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I.S.S.N.: 0212-5919Dep. Leg.: C379-83Nº 26 (2) - 2010

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Volume 26(2)

THALASSASAN INTERNATIONAL JOURNAL OF MARINE SCIENCES

This volumen includes selected papers presented in the ISMS09

Referees of Special Volume 26 (2) (ISMS09)

ANTONINA DOS SANTOSCRISTIAN ALDEA VENEGAS

EMILIO ROLÁNEVA CACABELOS REYES

FLORENCIO AGUIRREZABALAGA ELOSEGUIFRANCISCO VELASCO GUEVARA

FREE ESPINOSA TORREGERMÁN RODRÍGUEZ

JESUS SOUZA TRONCOSOJORGE TERRADOS

JOSÉ MANUEL GUERRA GARCÍAJOSE MOLARES VILA

JUAN MOREIRA DA ROCHAJULIO PARAPAR VEGAS

MANUEL ESPINO INFANTESMARCELA ASTORGA

MARCOS RUBALMINIA MANTEIGAROLAND HOUARTUNAI GANZEDO

VICENTE PÉREZ MUÑUZURRIVICTORIANO URGORRI CARRASCO

YOLANDA LUCAS RODRÍGUEZ

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ALFREDO ARCHE MIRALLESInstituto de Geología Económica. C.S.I.C., Madrid (Spain)

ANTONIO CENDRERO UCEDAD.C.I.T.T.Y.M. Facultad de CienciasUniversidad de Cantabria, Santander (Spain)

DARÍO DÍAZ COSÍNDepartamento de ZoologíaFacultad de Biología, Universidad Complutense de Madrid (Spain)

GRAHAM EVANSDepartment of Geology. Imperial CollegeThe London University (United Kingdom)

FERNANDO FRAGA RODRÍGUEZInstituto de Investigacións MariñasC.S.I.C., Vigo (Spain)

JOSÉ MARÍA GALLARDO ABUÍNInstituto de Investigacións Mariñas. C.S.I.C., Vigo (Spain)

FEDERICO ISLACentro de Geología de CostasUniversidad de Mar del Plata (Argentina)

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RICARDO RIGUERA VEGADepartamento de Química OrgánicaUniversidade de Santiago de Compostela (Spain)

RAFAEL ROBLES PARIENTEInstituto Español de OceanografíaMadrid (Spain)

AGUSTÍN UDÍAS VALLINADepartamento de GeofísicaFacultad de Física, Universidad Complutense de Madrid (Spain)

CARMINA VIRGILI RODÓNDepartamento de EstratigrafíaFacultad de Geología, Universidad Complutense de Madrid (Spain)

TAKESHI YASUMOTODepartment of ChemistryAgricultural Faculty,University of Tohoku (Japan)

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JESUS SOUZA TRONCOSOUniversity of Vigo

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INDEXJuan Moreira, Antía Lourido & Jesús S. TroncosoTemporal dynamics of the benthic assemblage in the muddy sediments of the Harbour of Baiona (Galicia, NW Iberian Peninsula).

Manuel González, Almudena Fontán, Ángel Borja, Andrea Del Campo, Ganix Esnaola, Luis Ferrer, Nerea Goikoetxea, Julien Mader, Adolfo Uriarte & Victoriano ValenciaTrend analysis of multidecadal datasets of air and sea surface temperatures within the southeastern bay of Biscay.

Xandro García-Regueira, Ramiro Tato, Juan Moreira & Victoriano UrgorriTemporal evolution of polychaete assemblages on intertidal hard substrata at two localities of the Galician coast after the “Prestige” oil spill.

Cristian Aldea & Jesús S. TroncosoRemarks on the Genus Trophon (s.l.) Montfort, 1810 (Mollusca: Gastropoda: Muricidae) in the southern ocean and adjacent areas.

Y. Ouagajjou, A. Aghzar, M. Miñambres, P. Presa & M. PérezDifferential gene flow between populations of Mytilus galloprovincialis distributed along Iberian and north African coasts.

Guillermo Díaz-Agras, Juan Moreira, Ramiro Tato, Xandro García-Regueira & Victoriano UrgorriDistribution and population structure of Patella vulgata linnaeus, 1758 (Gastropoda: Patellidae) on intertidal seawalls and rocky shores in the “ría de Ferrol” (Galicia, NW Iberian peninsula).

Eva Cacabelos, Juan Moreira & Jesús S. Troncoso Distribution and ecological analysis of the Syllidae (Annelida, Polychaeta) From the “ensenada de San Simón” (Galicia, NW Spain).

Mar Benavides, Fidel Echevarría, Reyes Sánchez-García, Natalia Garzón & Juan Ignacio González-GordilloMesozooplankton community structure during summer months in the bay of Cádiz.

M. Owner-Petersen, T. Andersen, P. Thejll, H. Gleisner, A. Ardeberg & A. UllaThe earthshine telescope project.

A. Pita, P. Presa & M. PérezGene flow, multilocus assignment and genetic structuring of the european hake. (Merluccius Merluccius)

Juan E. Guillén, Santiago Jiménez, Joaquín Martínez, Alejandro Triviño, Yolanda Múgica, José Argiles & Marisa BuenoExpansion of the invasive algae Caulerpa racemosa var. Cylindracea (sonder) Verlaque, Huisman & Boudouresque, 2003 on the region of Valencia Seabed.

S. Gaztelumendi, M. González, J. Egaña, A. Rubio, I.R. Gelpi, A. Fontán, K. Otxoa De Alda, L. Ferrer, N. Alchaarani, J. Mader & Ad. UriarteImplementation of an operational Océano-Meteorological system for the Basque country.

Cristian Aldea, Guillermo Díaz-Agras, Óscar García-Álvarez, Juan Moreira, Marcelo Rodrigues, Ramiro R. Tato, Victoriano Urgorri & Jesús S. TroncosoDeep-sea macrobenthic diversity and assemblages of “a selva”(NW Iberian peninsula): First Approach from samples taken aboard r/v Sarmiento de Gamboa.

9-22

23-31

33-45

47-73

75-78

79-91

93-102

103-118

119-128

129-133

135-149

151-167

169-179

Cover Photograph:“Opisthobranch mollusc of the genus

Polycera on Zostera meadowin the Inlet of O Grove. “.

Photograph courtesy of Jesús Souza Troncoso

TEMPORAL DYNAMICS OF THE BENTHIC ASSEMBLAGE IN THE MUDDY SEDIMENTS OF THE HARBOUR OF BAIONA

(GALICIA, NW IBERIAN PENINSULA)

ABSTRACT

Construction of artificial structures on the shoreline such as seawalls, breakwaters and jetties translates, in many cases, in changes in local current dynamics, alteration of sedimentation rates, siltation and organic enrichment. The temporal variation of the benthic fauna inhabiting the muddy sediments at the harbour of Baiona (Galicia, Spain) sheltered by an extensive breakwater was studied from May 1996 to May 1997 by means of quantitative sampling. Sediment was characterized by high content of silt and total organic matter; these results contrast to previous studies done in the same area, which reported a

dominance of sandy fractions in the sediment. A total of 17987 individuals representing 187 different taxa belonging to 11 phyla were found. The polychaete, Cossura pygodactylata, and the bivalve, Thyasira flexuosa, were the numerically dominant species at the studied site. Number of species, total abundance and densities of dominant species showed great monthly fluctuations and no clear seasonal patterns of temporal evolution could be detected. Values of diversity and evenness were, in general, high and stable through time. The composition of the assemblage was richer than that of assemblages from similar muddy sediments in other harbour areas from Europe but was poorer than those inhabiting surrounding sandy sediments at the Ensenada de Baiona. The values of the AMBI index and the numerical dominance of opportunistic species such as some deposit-feeding polychaetes indicated some degree of disturbance possibly linked to pulses in organic input derived from human activities in the area and, in first instance, to the construction of the harbour breakwater several decades ago.

(1) Estación de Bioloxía Mariña da Graña, Universidade de Santiago de Compostela, Casa do Hórreo, Rúa da Ribeira 1, E-15590, A Graña, Ferrol, Spain.e-mail: [email protected]

(2)Departamento de Ecoloxía e Bioloxía Animal, Facultade de Ciencias, Campus de Lagoas-Marcosende s/n, Universidade de Vigo, E-36310 Vigo, Spain.

Thalassas, 26 (2): 9-22An International Journal of Marine Sciences

Key words: benthic macrofauna, sediment, subtidal,organic matter, temporal dynamics, Ensenada de Baiona,

Iberian Peninsula, Atlantic Ocean.

JUAN MOREIRA(1), ANTÍA LOURIDO(2) & JESÚS S. TRONCOSO(2)

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INTRODUCTION Seasonal variation of benthic assemblages

depends on a number of abiotic and biotic factors such as hydrodynamism, granulometric composition of the sediment, food supply, predation and competition (e.g. Buchanan et al., 1974; Gray, 1981; Josefson & Rosenberg, 1988). In addition, activities derived from human population concentrating in coastal areas also strongly affect benthic assemblages. Among these activities, sewage disposal, dredging, fishing, mollusc harvesting and construction of artificial structures have, in general, a negative impact on benthic faunas by reducing biodiversity, facilitating the spread of invasive species or fragmenting the natural habitats (López-Jamar & Mejuto, 1988; Fairweather, 1990; Thrush et al., 1998; Guerra-García et al., 2003; Çinar et al., 2006).

The Galician rias (NW Spain) are characterized by having highly diverse benthic faunas which is due, in part, to the great variety sedimentary habitats present in the rias. In addittion, the shoreline of the rias is increasingly getting more urbanized because of the construction of seawalls, breakwaters and marinas. The presence of these artificial structures affects, in many cases, to the local hydrodynamic regimes usually resulting in alteration of sedimentation rates, increased siltation and organic enrichment (Alejo & Vilas, 1987; Martí et al., 1995; Evans, 2008). This results in further alterations of physical parameters of the sediment including granulometry, which affects, in turn, to the composition and structure of the benthic assemblage (Pearson & Rosenberg, 1978; Martin et al., 2005). For example, high increases in organic matter usually favours to oportunistic deposit-

JUAN MOREIRA, ANTÍA LOURIDO & JESÚS S. TRONCOSO

Figure 1: Location of the Ensenada de Baiona and sampling site.

feeder species thus resulting in empoverished assemblages which are numerically dominated by a few species, mostly polychaetes (Pearson, 1975; Grall & Chauvaud, 2002).

The Ensenada de Baiona is a small inlet located

in the southern margin of the Ría de Vigo, and is exposed to oceanic swell for most of the year (Alejo et al., 1999). During the 70’s, a extensive breakwater was built to shelter the harbour of Baiona (Alejo & Vilas, 1987). Sediments at those area were sandy but previous work has pointed out that granulometric composition is expected to get muddier (Alejo & Vilas, 1987). Data on abundance and recruitment for three bivalve species inhabiting those sediments have been provided by Veloso et al. (2007). In this paper, we describe the temporal dynamics of the whole benthic assemblage from a shallow subtidal muddy site sheltered by the harbour breakwater to test whether the granulometric composition and the fauna has changed according to previous observations and in comparison to other sandy areas at the inlet.

MATERIALS AND METHODS

Study area

The Ensenada de Baiona is located on the southern margin of the mouth of the Ría de Vigo, between 42º07’N-42º09’N and 08º51’W-08º49’W. Salinity ranges from 32‰ in winter to 35‰ in summer in the outer area, and from 28‰ to 35‰ in the harbour area. The western outer margin is exposed to the oceanic swell and winter winds (Alejo et al., 1999). Sediments are mostly sandy and their distribution follows a gradient in grain size (Alejo et al., 1999; Moreira et al., 2005). The harbour jetty built during the 1970s shelters the southern area around the harbour of Baiona (Alejo & Vilas, 1987); sediments range from sandy mud to mud with contents in silt/clay from 50% to 90% (Moreira et al., 2005). The harbour is mostly used by recreational and fishing vessels.

Sampling

The sampling site is located at a shallow subtidal muddy bottom (2 m depth) within the harbour of Baiona (42º07’19’’N; 08º50’45’’W; Figure 1). Quantitative sampling was done in a monthly basis from May 1996 to May 1997. Five replicates were taken on each date using a Van Veen grab with a sampling area of 0.056 m2 thus covering a total area of 0.28 m2. Samples were sieved through a 0.5 mm mesh and fixed in 10% buffered formalin for later sorting and identification of the fauna. An additional sediment sample was taken at each sampling date to determine granulometric composition,

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TEMPORAL DYNAMICS OF THE BENTHIC ASSEMBLAGE IN THE MUDDY SEDIMENTSOF THE HARBOUR OF BAIONA (GALICIA, NW IBERIAN PENINSULA)

Figure 2: Proportion of faunistic groups (A) and trophic strategies (B) for

each sampling date. Legend to (A): P, polychaetes; M, molluscs; C, crustaceans; O, others. Legend to (B): C, carnivores; SD, surface

deposit-feeders; SSD, sub-surface deposit-feeders; S,suspensivores; O, others.

grain-size median (Q50), sorting coefficient (So) and total organic matter (TOM, %). The following sedimentary fractions were considered: gravel (>2 mm), very coarse sand (2-1 mm), coarse sand (1-0.5 mm), medium sand (0.5-0.25 mm), fine sand (0.25-0.125 mm), very fine sand (0.125-0.063 mm), silt (0.063-0.0039 mm) and clay (<0.0039 mm). The total organic matter content was estimated from the weight loss on combustion at 450ºC for 4 hours.

Data analyses

Temporal variations of the structure and richness of the assemblage was investigated by calculating the following biotic parameters: total abundance (N), number of species (S), the Shannon-Wiener diversity index (H’, log2) and Pielou’s evenness (J); those were determined for each sampling date. A one-factor ANOVA (Analysis

of Variance) was used to test whether those parameters and the abundance of the numerically dominant species showed significant differences among sampling dates; the homogeneity of variances was previously evaluated by means of Cochran’s C test. Where ANOVA showed significant differences (p<0.05), a post hoc Student-Newman-Keuls (SNK) test was then done for a posteriori comparisons of the means from each sampling date. To describe the trophic composition of the benthic assemblage, taxa were assigned to one of the five feeding strategies usually considered in the literature, i.e., carnivores, surface deposit-feeders, sub-surface deposit-feeders, suspensivores and others (herbivores, scavengers, omnivores).

The AMBI (AZTI Marine Biotic Index) proposed by Borja et al. (2000) was used in order to investigate the ecological quality of the bottom. The procedure

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Table 1: Mean monthly density (individuals per m2), total numerical dominance (%) and presence (%) of the dominant taxa at the studied site.

consists of the calculation of the Biotic Coefficient (BC) which is based on the proportions of five (I-V) ecological groups of benthic taxa; those groups are defined by their sensitivity/tolerance to environmental stress. Values of the BC are referred to the AMBI in a range from 0 (unpolluted) to 7 (extremely polluted). The validity of this index has been successfully tested for several areas of the European coast (e.g. Borja et al., 2003; Muxika et al., 2005). The software available at http://www.azti.es was used for index computation.

In order to detect any patterns in evolution of the assemblage through time, multivariate analyses were done through the PRIMER 6 software package (Clarke & Gorley, 2006). A similarities matrix between samples was constructed by means of the Bray-Curtis similarity index by first applying

square root transformation on species abundance to downweight the contribution of the most abundant species. Data were previously averaged across the five replicates for each date thus obtaining a centroid. From the similarities matrix, samples (centroids) were classified by cluster analysis based on the group-average sorting algorithm. Clusters of samples determined as statistically significant by profile test SIMPROF (p<0.05) were considered as having a similar faunistic composition. Non-metric multidimensional scaling (nMDS) was used to visualize the ordination of centroids.

The possible relationship between benthic fauna and the measured sedimentary variables was explored using the BIO-ENV procedure (PRIMER). All variables expressed in percentages were previously transformed by log (x+1).

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Figure 3: Temporal variation in (A) number of species, (B) number of individuals, (C) diversity (Shannon-Wiener’s index) and (D) Pielou’s evenness

(mean per replicate + standard error) at the sampling site in the Ensenada de Baiona.

RESULTS

Sedimentary parameters

Sediment was mostly composed by silt (70.1±4.1%) during all the sampling period, ranging from 64% in March 1997 to 78% in December 1996. Very fine sand was the second granulometric fraction in content (16.9±2.6%) followed by clay (5.0±0.6%). Grain-size median corresponded to the silt fraction; sorting coefficient ranged from moderate to poor. Content in total organic matter was high (10.0±1.7%); values descended at the end of the period of study, ranging from 13.1% in May 1996 to 8.6% in May 1997.

Faunal composition

A total of 17987 individuals corresponding to 187 different taxa and 11 phyla were found. Polychaete

annelids and bivalve molluscs were the numerically dominant groups representing, respectively, 42% and 31% of total abundance. The most diverse groups in number of species were polychaetes (68) and crustaceans (57). The most abundant species were the polychaete, Cossura pygodactylata (16% of total abundance; Table 1), and the bivalve, Thyasira flexuosa (13%), followed by the bivalves, Mysella bidentata, Loripes lacteus and Abra nitida, the polychaetes, Exogone hebes and Capitella capitata, and two tubificid oligochaetes. In total, 17 species out of 187 contributed up to the 75% of total abundance and the first six up to the 50% (Table 1); many of those species were present in the assemblage for most of the year and had great variations in density through time as shown by the values of the standard deviation. About 56% of all species were represented by less than 10 individuals through all the sampling period.

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Figure 4: Temporal variation in density (mean per replicate + standard deviation expressed as individuals per m2) of selected numerically dominant species.

(A) Cossura pygodactylata, (B) Mysella bidentata, (C) Tubificidae sp. 1, (D) Tubificidae sp. 2.

Temporal evolution of the assemblage

Polychaetes and molluscs (mostly bivalves) dominated numerically the assemblage for most of the studied period (Figure 2A). The contribution of crustaceans was low apart from samples of July when sediment was covered by ulvacean algae; other groups such as tubificid oligochaetes had a greater numerical presence in samples from January and April. Both types of deposit-feeders were the most abundant trophic groups, constituting between 60% and 85% of total monthly abundance; carnivores and suspension feeders had each, in general, monthly dominances of less than 10% (Figure 2B).

Total number of species showed the lowest values in autumn and the highest in late summer, January and April (Figure 3A); values had, in general, great variations from month to month. Total abundance was stable from May to September (Figure 3B); minimal annual values were recorded in October and December with a posterior increase between January and April followed by a marked decrease by the end of the studied period. Diversity showed high values for most of the year (>3 bits; Figure 3C); evenness values did not greatly vary between either seasons or consecutive months and were always equal or greater than 0.7 (Figure 3D). Although all univariate parameters showed significant differences among sampling dates (Table 2), SNK tests only detected significant groups of samples for number of individuals.

The numerically dominant species showed different patterns of temporal evolution. The abundance of C. pygodactylata and T. flexuosa showed significant differences among sampling dates (Table 2) and great fluctuations in abundance between consecutive months (Figure 4A); the former showed its maximal abundance in November but densities tended to be lower in autumn. For T. flexuosa, the highest densities were detected in late summer and between January and April. On the

contrary, M. bidentata did not show great variations in abundance for most of the year (Figure 4B); maximal densities were recorded between March and April and then in May 1997 numbers decreased and were lower than those of May 1996. The oligochaete Tubificidae sp. 1 showed three peaks of abundance in June, April and the greatest density in January; the rest of the year abundance was low (Figure 4C). The oligochaete Tubificidae sp. 2 showed a similar pattern to the aforementioned species; peaks of abundance occured between January and April (Figure 4D).

The values of the AMBI index showed that the sampling site has some degree of disturbance, ranging from slightly disturbed to moderately disturbed (Figure 5A). In general, ecological groups III and IV (tolerant to pollution and second-order opportunistic species, respectively) were the numerically dominant ones for most of the studied period, being the only exception the sample from July when group I (sensitive species) accounted for >50% of the fauna (Figure 5B). First-order opportunistic species (group V) only had a contribution to total abundance greater than 20% in June, January and May 1997.

Multivariate analyses

Cluster analysis and SIMPROF test detected five different groups of monthly samples based on abundance data: two groups were constituted by samples from late spring and summer and other three composed by samples from autumn to early spring (Figure 6); the latter were located at the left of the graphic representation of the nMDS and the former at the center. The samples of July did not belong to any group and were the most dissimilar in comparison to the others; this was due, in part, to the lowest abundances of several infaunal numerically dominant species such as T. flexuosa, M. bidentata and the tubificids, and to the greater presence of epifaunal crustaceans (e.g. the amphipods, Microdeutopus anomalus and Pthisica marina, and the shrimp, Palaemon elegans).

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The BIO-ENV procedure showed, in general, low correlations among faunistic data and any combination of the measured sedimentary variables (pw<0.4). The greatest correlations were obtained for content of coarse silt (pw: 0.451) and the combination of coarse silt and grain-size median (pw: 0.448).

DISCUSSION

This study has shown that the sedimentary composition of the area sheltered by the breakwater of the harbour of Baiona has, as expected, turned from sandy to muddy in the last decades after the construction of that structure (Alejo & Vilas, 1987). In addition, the composition of the faunal assemblages now inhabiting those soft bottoms agrees with that of shallow subtidal muddy sediments reported elsewhere in temperate European waters (e.g. López-Jamar & Parra, 1997; Çinar et al., 2006). In general, soft-bottom benthic assemblages inhabiting inner harbour areas are impoverished and numerically dominated by a few opportunistic species, mostly polychaetes (Thompson & Shin, 1983; Je et al., 2003; Çinar et al., 2006). Those areas are also characterized by the low number of species of crustaceans due, in many cases, to their sensitivity to the pollutants which are usually disposed there (Estacio et al., 1997; Guerra-García & García-Gómez, 2004). On the contrary, the muddy site studied at the harbour of Baiona showed a richer assemblage than those reported from similar areas (Estacio et al., 1997; Grall & Glémarec, 1997; Rebzani-Zahaf et al., 1997; Dhainaut-Courtois et al., 2000). Total number of species (187) and diversity values (>3 bits) were high for such a kind of sediment; crustaceans (mostly peracarids) were present for most of the year although in lower numbers than polychaetes and bivalves. The high total number of species could be due to an “edge effect” because of the presence of species typical from nearby sandy sediments, such as some species of bivalves, peracarid crustaceans and polychaetes (Ergen et al., 2006). The assemblage was, however, dominated by deposit-feeding polychaetes and opportunistic ubiquitous species such as the poychaetes, Cossura

pygodactylata and Capitella capitata, and the bivalve, Thyasira flexuosa (Bachelet & Laubier, 1994; López-Jamar & Parra, 1997). These species are characteristic of estuarine muddy sediments which are subjected to disturbances and have a flexible life-history which allows them a posterior recolonisation of the sediment after perturbation (López-Jamar & Mejuto, 1988; Newell et al., 1998).

There were no conspicuous seasonal trends in the number of species and individuals in the studied assemblage at the harbour of Baiona. Similar results have been reported for other harbour areas in

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Figure 5: Mean values of AMBI (± standard deviation) for each sampling date

(A) and relative abundance of ecological groups according to the AMBI classification (B). I, disturbance-sensitive; II, disturbance

indifferent; III, disturbance-tolerant; IV, second-order opportunistic; V, first-order opportunistic.

temperate latitudes (e.g. Ergen et al., 2006). In the same way, numerically dominant species showed great variations in abundance between consecutive monthly samplings (cfr. Figure 4). In the case of bivalves, this fact seems to be related to successful recruitment, mostly between winter and spring (Veloso et al., 2007), which is responsible for the peaks in abundance observed in January and April. Çinar et al. (2006) detected similar patterns for benthic assemblages in Alsancak harbour (eastern Mediterranean) where maximal abundances occurred in spring; this was mostly due to an increase in number of juveniles of polychaetes and bivalves. At the harbour of Baiona, values of diversity and evenness were, in general, high and relatively stable through time. Low values of diversity are considered a symptom of perturbation (Simboura & Zenetos, 2002) but also reflect the seasonal changes of benthic assemblages in normal conditions, mostly when drastic increases in abundance of some species occur (Reiss & Kröncke, 2005). In our case, although those values suggest a good condition of the benthic assemblage it must be

taken into account that dominant species for most of the year are those considered as opportunistic (López-Jamar & Mejuto, 1988; Bachelet & Laubier, 1994). Although the AMBI index and nMDS ordination showed some discrepancies in the plotting of some samples from late winter and spring, values of the AMBI index pointed out symptoms of perturbation according to the relative abundance of ecological groups. This suggests that the assemblage may be subjected to any kind of perturbation, possibly related to pulses in organic input due to urban sewage. In fact, content in total organic matter of the sediment was high for all the sampling period (>7%), with maximal values of between 11% and 13% from May to December 1996; the latter period also coincided with the lowest abundances of several numerically dominant species. In general, an increase in the amount of organic matter in the sediment may initially induce further increases in the abundance of species which are followed by a subsequent diminution as the organic input rises and phenomena of anoxia occur in the sediment (Gray, 1979). Nevertheless, correlation

17


Figure 6: nMDS ordination of monthly samples based on abundance data (centroids). Groups of samples determined by the SIMPROF test are shown.

analyses done among the abundance of dominant species and the content of organic matter did not show significant results.

The numerically dominant species at the studied site, i.e. Cossura pygodactylata and Thyasira flexuosa, have previously been related to events of organic enrichment. The former is considered as an opportunistic species (Glémarec & Grall, 2000), which is able to proliferate in organically enriched sediments similarly as Capitella capitata does. Bachelet & Laubier (1994) reported densities of C. pygodactylata in muddy sediments of the Bay of Arcachon (Atlantic coast of France) of between 4800 and 32000 individuals per m2; numbers rise after recruitment occurring between April and May followed by a decline in abundance and then a posterior recovery in the next spring (Bachelet & Laubier, 1994). At the Ensenada de Baiona, the maximal abundance was, however, detected in August, being present in the assemblage all the year round. On the other hand, T. flexuosa has been reported as an abundant species in muddy sediments polluted by urban and industrial sewage (López-Jamar & Parra, 1997); this species is able to colonise sediments affected by dredging activities taking advantage of the lack of competitors (López-Jamar & Mejuto, 1988). In the

Ría da Coruña, this species is particularly abundant and had densities of up to 22000 individuals per m2 (López-Jamar & Parra, 1997). At the studied site, T. flexuosa also showed high densities which are greater than those recorded in other southern rias such as those of Vigo, Pontevedra, Arousa and Muros (López-Jamar & Parra, 1997). López-Jamar et al. (1995) pointed out that those and similar species are able to respond to frequent disturbance events occurring in harbour areas because they have short life-cycles, several periods of recruitment in the same year and high reproductive rates. On the contrary, assemblages present in more stable sediments, not subjected to periodical perturbations, are characterised by species which have longer life-cycles and only one period of recruitment each year, showing more conspicuous seasonal and annual variations, mostly due to eventual fails in recruitment (López-Jamar et al., 1995). Therefore, the regular presence and the observed fluctuations in abundance of the two aforementioned species may be indicative of regular disturbance at the studied site at the Ensenada de Baiona.

Crustaceans were numerically dominant only in samples of July, when sediment was covered with ulvacean algae and infaunal species were, in general, less abundant than in other monthly samples.

Table 2: Summary of ANOVA results for comparisons of number of species (S), number of individuals (N), Shannon-Wiener’s diversity index (H’), Pielou’s evenness (J) and abundance of Cossura

pygodactylata and Thyasira flexuosa among sampling dates. n = 5; df = 12; ns, not significant (P > 0.05); *P < 0.01; ** P < 0.001. Results of SNK tests are only shown when significant.

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Macroalgal blooms are becoming increasingly common in sheltered shallow areas, mostly in spring and summer (Bolam et al., 2000; Jones & Pinn, 2006). Those blooms are dependent on nutrient availability and shallow areas with low water renewal are more susceptible to develop macroalgal blooms whenever the organic input increases (Grall & Chauvaud, 2002). In addition, their effects are similar to those derived from organic enrichment (Pearson & Rosenberg, 1978). Thus, the extensive presence of macroalgae affects the physico-chemical features of the sediment-water interface and those of the sediment itself, often leading to reduction in the current velocity and the subsequent siltation, anoxia and accumulation of hydrogen sulphide (Norkko, 1998; Bolam et al., 2000; Lopes et al., 2000; Jones & Pinn, 2006). In general, this proliferation of macroalgae favours in first instance to epibenthic species such as peracarid crustaceans (Raffaelli et al., 1998; Bolam et al., 2000). On the contrary, alteration of the sediment may lead to changes in faunistic composition and reduction in a number of infaunal species (Raffaelli et al., 1991; Jones & Pinn, 2006), also favouring the proliferation of opportunistic species (Thrush, 1986) and preventing recruitment of bivalves (Currás & Mora, 1996). In our case, the later fact was possibly reflected in the poor summer recruitment of the bivalve Loripes lacteus (Veloso et al., 2007).

Although the benthic assemblage studied here is more diverse than others from similar muddy areas is, however, less diverse than those inhabiting sandy sediments found in other parts of the Ensenada de Baiona (Moreira & Troncoso, 2008). In fact, total number of species and abundance of macrofauna is lower than in the medium and fine-sand sediments of the central area of the inlet. Indeed, the construction of the harbour breakwater has induced great changes in the dynamics of currents in this area (Alejo & Vilas, 1987); this has resulted in increased siltation and a subsequent change in the granulometric composition, which was originally dominated by fine and very fine sand (Alejo & Vilas, 1987). Furthermore, these

alterations in sedimentation rates may also favour the deposition of organic matter from the Miñor river which flows nearby and that from urban sewage of the town of Baiona. Although previous data on the benthic assemblages of the area now sheltered by the harbour breakwater are not available, it is likely that the original assemblage was similar to that present on the fine-sand sediments; the later are characterised by a greater presence of bivalves such as Tellina tenuis, T. fabula and Chamelea striatula, magelonid polychaetes, and particularly by a more diverse peracarid fauna (Moreira et al., 2005, 2006, 2008). This overall situation has also been reported for the harbour of Valencia (Martí et al., 1995) and Ceuta (Guerra-García & García-Gómez, 2004), being benthic assemblages more diverse in the surrounding sandy sediments not sheltered by artificial structures. In short, the sum of those alterations would lead to an impoverished and less structured benthic assemblage, both regarding faunistic and trophic composition, and numerically dominated by deposit-feeding species, mostly opportunistic ones such as cossurid and capitellid polychaetes (Planas & Mora, 1989; Palacio et al., 1993).

These results emphasize again the necessity of a better management when urbanising the shoreline. Indeed, there is a proliferation in the construction of artificial structures such as jetties, breakwaters and piers on the shoreline (Chapman, 2003) which leads, in many cases, to changes in local hydrodynamic conditions, preventing movement of currents and allowing organic enrichment which leads to granulometric changes, anoxia and macroalgal blooms; this usually translates, in turn, into a loss of benthic biodiversity (Martí et al., 1995; Salen-Picard et al., 1997; Guerra-García & García Gómez, 2004). Simple measures such as the construction of channels under breakwaters and jetties may help to maintain current movement, reducing sedimentation rates and organic pollution and thus allowing the establishment of richer benthic assemblage as it has been pointed out for the harbour of Ceuta (Guerra-García & García-Gómez, 2004).

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ACKNOWLEDGEMENTS

The authors want to express their gratitude to F.J. Cristobo, C. Olabarria, P. Quintas and P. Reboreda for their help during field work. Comments from two anonymous referees are greatly acknowledged.

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TREND ANALYSIS OF MULTIDECADAL DATASETS OF AIR AND SEA SURFACE TEMPERATURES WITHIN THE

SOUTHEASTERN BAY OF BISCAY

ABSTRACT

The results of the trend analysis of air and sea surface temperatures measured in Donostia-San Sebastián, southeastern Bay of Biscay, are described within this contribution. The air temperature data series belongs to the Meteorological Observatory of Igeldo (AEMET) (43° 18’ N, 02° 02’ W; at 252 m above the mean sea level). The time series extends from 1928 to 2008, representing 81 years of daily maximum and minimum air temperatures. The sea surface temperature (SST) dataset, measured in a nearly daily basis at 10 a.m. at the Aquarium of

Donostia-San Sebastian (43° 19’ N, 02° 00’ W), extends from 1947 to 2008; representing 62 years of data. In order to remove fluctuations due to time-scales of less than a year (such as seasonal variability), an annual moving average has been calculated. Subsequently, a trend analysis has been performed with the annual air and sea surface temperature data, by linear regression fitting and by minimising absolute deviation. Globally, a slightly decreasing trend (-0.003 °C·year-1) can be observed, for the whole of the SST time series (1947-2008). In contrast, a warming trend of 0.008 and 0.011 °C·year-1 is detected for the minimum and maximum air temperature series (1928-2008), respectively. However, the analysis of both time series, in a decadal basis, shows a remarkable warming trend since the mid 1980s. Such increase is of 0.019 and 0.026 °C·year-1 for the annual averaged minimum and maximum air temperatures; whilst it is of 0.019 °C·year-1, for the annual averaged SST.

(1) Marine Research Division, AZTI-Tecnalia,Herrera Kaia – Portualdea z/g, 20110, Pasaia, Gipuzkoa, Spain, www.azti.ese-mail: [email protected]


Key words: Warming trend, SST, air temperature, Bay of Biscay, Basque coast, Iberian Peninsula, Atlantic Ocean.

MANUEL GONZÁLEZ(1), ALMUDENA FONTÁN(1), ÁNGEL BORJA(1), ANDREA DEL CAMPO(1), GANIX ESNAOLA(1), LUIS FERRER(1), NEREA GOIKOETXEA(1), JULIEN MADER(1), ADOLFO URIARTE(1) & VICTORIANO VALENCIA(1)

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24

MANUEL GONZÁLEZ, ALMUDENA FONTÁN, ÁNGEL BORJA, ANDREA DEL CAMPO, GANIX ESNAOLA, LUIS FERRER, NEREA GOIKOETXEA,JULIEN MADER, ADOLFO URIARTE & VICTORIANO VALENCIA

INTRODUCTION

Although the reliability and accuracy of the numerical models have increased over the last years, the studies concerning the global change must be sustained within the analysis of long time series. Additionally, monitoring needs to be continued from year to year, in order to extract natural cycles of varying frequency and develop predictive capacity (Southward, 1995). Moreover, such long time series are essential to analyse both natural and human-induced fluctuations. Above all, such series are of crucial interest to detect potential impacts of climate

change on marine ecosystems and to promote efficient adaptation strategies.

At global scale, eleven of the last twelve years (1995-2006) rank among the twelve warmest years in the instrumental record of global surface temperature (since 1850). The 100-year linear trend (1906-2005) of 0.74 ± 0.18 °C is larger than the trend of 0.6 ± 0.2 °C corresponding to the period 1901-2000. The linear warming trend over the 50 years from 1956 to 2005 (0.13 ± 0.03 °C·decade-1) is nearly twice that for the 100 years from 1906 to 2005 (IPCC, 2007; Trenberth et al., 2007).

Figure 1: The location of the study area (shaded rectangle) and of the monitoring stations, in detail. Bathymetry in meters.

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TREND ANALYSIS OF MULTIDECADAL DATASETS OF AIR AND SEA SURFACE TEMPERATURESWITHIN THE SOUTHEASTERN BAY OF BISCAY

Europe has warmed more than the global average. The increase for the European continental area and European continental and ocean area has been 1.16 °C and 0.95 °C, respectively, comparing the trend towards 2006 with pre-industrial times (CRU, 2006). The warmest year in European continental has been 2000, closely followed by 2006 and 2002. The temperature changes have been largest in south-western, central and north-eastern Europe and in mountainous regions (Jones and Moberg, 2003). The annual average temperature for Europe is projected to rise this century1-5.5 °C (comparing 2080-2100 with 1961-1990 average), taking into account the uncertainties in future socio-economic development and in climate models (Christensen and Christensen, 2007). The warming is projected to be greatest over Eastern Europe and Scandinavia in winter (December to February), and over south-western and Mediterranean Europe in summer (June to August) (Giorgi et al., 2004; Christensen and Christensen, 2007). Especially south-western Europe may experience a considerable warming in summer, exceeding 6 °C in parts of France and the Iberian Peninsula (IPCC, 2007).

Comparatively, Spain has warmed, on average, more than Europe (1.2-1.5 ºC over the last century). Likewise, during the 20th century and particularly within the last third of the century, such increase has been more pronounced in spring and summer. From 1850 to 2003, the annual average maximum and minimum daily temperatures have increased of about 0.12 ºC·decade-1 and 0.10 ºC·decade-1, respectively (Ministerio de Medio Ambiente, 2007).

The studies relating to climate change, undertaken within the Basque coastal area, are those from Koutsikopoulos et al. (1998), Borja et al. (2000), Valencia et al. (2003; 2004), González et al. (2008a, 2008b), Fontán et al. (2008) and Goikoetxea et al. (2009). In this context, several aspects relating changes in temperature were identified. Koutsikopoulos et al. (1998) concluded that the southeastern part of the Bay of Biscay showed the strongest warming trend (an increase of SST of 0.064 °C·year-1 for the period 1972-1993). Borja et al. (2000) reported that air temperature and solar irradiance explain most of the SST seasonal and interannual variability, within the Basque coastal area. Additionally, the vapour stress and the relative humidity, the upwelling-downwelling indices or the turbulence appeared to modulate SST, with different seasonal strength and statistical significance (Borja et al., 2000). Valencia et al. (2003; 2004) postulated that the concavity of the southeastern corner of the Bay of Biscay (Figure 1) results in a strong continental influence over the region. As a consequence, shelf waters are warmer in summer and fresher and colder in winter than those of western areas at equivalent latitudes. As abovementioned, air temperature is the most direct and influential parameter with regard to the SST variations; both air and sea water temperatures show a marked seasonality, which is typical of temperate areas at mid-latitudes (Valencia et al., 2004). Thus, Fontán et al. (2008), found a significant coupling (r2=0.88; α<0.0001) between monthly average air temperature and SST at San Sebastián, for the period 1986-2005. Goikoetxea et al. (2009) concluded that

Table 1: Summary of the dataset, including source, record length and sampling rate (for locations, see Fig. 1).

*Station elevation (above sea level) and water depth (below sea level) (m).

26


the SST measurements in San Sebastián from 1947 to 2007, show a slightly decreasing trend. However, a warming trend is observed in the last three-decadal period.

In this context, one of the longest SST series is that of the Aquarium of San Sebastián, with 62 years of nearly daily SST measurements (Borja et al., 2000; González et al., 2008a; González et al., 2008b; Goikoetxea et al., 2009). Additionally, the air temperature series from Igeldo Observatory consists of 81 years of daily minimum and maximum temperatures.

Based upon the available long-term SST and air temperature series, the main objective of this investigation is to quantitatively determine changes and trends in temperature series, within the southeastern Bay of Biscay.

DATA AND METHODS

The study area is located in the southeastern Bay of Biscay between west-east oriented Spanish coast and the north-south oriented French coast (Figure 1). The coastal area can be characterised as being more influenced by land˙ climate and inputs, than other typically ‘open sea’ ˙areas (Valencia et al., 2004).

A description of the available data, including its source, record length and sampling rate, is presented in Table 1. Additionally, the location of the monitoring sampling stations is shown in Figure 1. The data utilised include measurements of SST at the Aquarium of Donostia-San Sebastián and of minimum and maximum air temperature at the Meteorological Observatory of Igeldo. The Aquarium monitoring station is located within La Concha Bay. The SST series extends from 1947 to 2008, representing nearly 62 years of data, recorded in a nearly daily basis at 10 a.m. The time series has gaps in the data, especially between 1967 and 1975; consequently, up to 22.8% of the total data set is missing. In this context, an EOF (Empirical Orthogonal Function) based on DINEOF

reconstruction of the SST measurements is proposed (see Álvarez-Azcárate et al. (2005), for more detail about methodology).

The Igeldo meteorological station is located at the Igeldo Mountain, at 252 m above mean sea level. The minimum and maximum air temperature series extends from 1928 to 2008. Such datasets are almost complete; the missing values are 13 and 116 days for the minimum and maximum air temperature series, respectively.

An annual-centred moving average was calculated, in order to remove fluctuations due to time-scales of less than a year (such as seasonal variability), taking into account missing data within the SST time series. The expression applied is as follows:

where p=(l-1)/2 is the half-width. In this particular case, l = 365 days and p = 182 days.

The uncertainty in the moving average estimations was calculated from:

where q is the number of data within a year-interval, being q=2•p for the air and sea surface temperature datasets.

The anomalies were determined by means of annual-centred moving average series, following

where:

27


N is the number of days for those annual-centred moving averages are calculated.

Subsequently, a trend analysis has been performed with the annual data by linear regression fitting (Press et al., 1989). The linear regression method is based on minimising the function:

where x and y are the independent and dependent variables, respectively. σi is the uncertainty estimation of yi and a and b are the regression coefficients.

RESULTS AND DISCUSSION

In order to provide confirmation and validation of the reconstruction method, 5% of available data were removed from the SST time-series and subsequently, reconstruction of the data was performed following the method of Álvarez-Azcárate et al. (2005). The reconstructed data,

corresponding to previously removed data, was further compared with real observations (Figure 2). The results show that the reconstruction independently reproduces instrumental estimates. Afterwards, reconstruction were again carried out with 100% of the observations.

A trend analysis performed with the annual-centred moving averaged (ACMA) SST data by linear regression fitting is shown in Figure 3. Globally, a slight cooling trend (-0.003 ºC·year-1) can be observed, for the whole of the time-series (Figure 3(a)). However, a change in the tendency is observed for the latter part of the series, 1986-2008, with a warming trend of 0.019 ºC·year-1 (Figure 3(b)). This positive trend can be detected even if extreme periods of hot weather, such as the summer 2003 and the second half of 2006, are removed from the analysis (González et al., 2008a).

In addition, a trend analysis with the minimum and maximum air temperature data has been estimated, by linear regression fitting (Figure 4). A warming trend of 0.008 and 0.011°C·year-1 is detected for the minimum and maximum air temperature series (1928-2008), respectively. However, the analysis of both time-series, in a decadal basis, shows a remarkable warming trend from 1986 to 2008. Such increase is of 0.019 and 0.026 °C·year-1 for the annual averaged minimum and maximum air temperatures (González et al., 2008b). That increase is in agreement with that described by Trenberth et al. (2007), 0.029 and 0.034 °C·year-1, in the Northern Hemisphere for the period 1979-2005.

The trend observed, relating minimum temperatures in San Sebastián within the period 1928-2008 as well as the period 1986-2008, is in agreement with that observed in the Northern Hemisphere for the period 1901-2005 (between 0.0063 y 0.0079 °C·year-1) (Trenberth et al., 2007). In contrast, the trend detected, for the maximum temperatures, is above that detected by Trenberth et al. (2007).

Figure 2:Validation of the reconstructed SST measurements, in the Aquarium

of San Sebastián, with DINEOF.

28

Figure 3: Annual-centred moving averaged (ACMA) SST data together with the trend for the periods: (a) 1947-2008 and (b) 1986-2008,

at the Aquarium of San Sebastián.

29


Figure 4: Annual-centred moving averaged (ACMA) air temperature measurements together with the trend for: (a) maximum air temperature within the period 1947-2008; (b) minimum air temperature within the period 1947-2008; (c) maximum air temperature within the period 1986-2008; and (d) minimum

air temperature within the period 1986-2008, at the Igeldo Meteorological station.

30


CONCLUSIONS

A slightly decreasing trend (-0.003 °C·year-1) can be observed, for the whole of the SST time series (1947-2008). In contrast, a warming trend of 0.008 and 0.011°C·year-1 is detected for the minimum and maximum air temperature series (1928-2008), respectively. However, a remarkable warming trend from 1986 to 2008 is observed. Such increase is of 0.019 and 0.026 °C·year-1 for the annual averaged minimum and maximum air temperatures; whilst it is 0.019 °C·year-1, for the annual averaged SST.

Long time-series, such as those presented here, are essential to analyse and detect trends and anomaly patterns. In this context, both the Aquarium SST series together with the Igeldo air temperature series, are of invaluable interest when determining trends, in the southeastern corner of the Bay of Biscay.

More research is needed, based on longer time-series, in order to corroborate that the existing trends are maintained in the future.

ACKNOWLEDGMENTS

The SST data were provided by the Oceanographic Society of Gipuzkoa. The air temperature data were obtained from the Meteorological Observatory of Igeldo AEMET, Spanish State Meteorological Agency). This study has been partially funded by the ETORTEK Strategic Research Programme (Basque Government, Department of Industry, Trade and Tourism and Department of Transport and Civil Works) through the projects EKLIMA21 and ITSASEUS and Caja Navarra Foundation (Social Activities Programme of Caja Navarra). G. Esnaola and N. Goikoetxea are supported by a research Grant from the Fundación Centros Tecnologicos, Iñaki Goenaga. This is contribution number 848, of the Marine Research Division of AZTI-Tecnalia.

REFERENCES

Alvera-Azcárate, A., Barth, A., Rixen, M. and Beckers, J., 2005. Reconstruction of incomplete oceanographic data sets using empirical orthogonal functions: application to the Adriatic Sea surface temperature. Ocean Model 9: 325-346.

Borja, Á., Egaña, J., Valencia, V., Franco, J., Castro, R., 2000. 1947-1997, estudio y validación de una serie de datos diarios de temperatura del agua del mar en San Sebastián, procedente de su Aquarium. Ozeanografika 3: 139-152.

Christensen, J.H. and Christensen, O.B., 2007. A summary of PRUDENCE model projections of changes in European climate by the end of this century. Climate Change 81(1): 7-30.

CRU. (2006). HadCRUT3 Temperature: Global. Climatic Research Unit, University of East Anglia. Retrieved 1-1-07, from http://www.cru.uea.ac.uk/cru/data/temperature.

Fontán, A., Valencia, V., Borja, Á. and Goikoetxea, N., 2008. Oceano-meteorological conditions and coupling in the southeastern Bay of Biscay, for the period 2001-2005: a comparison with the last two decades. Journal of Marine Systems 72: 167-177.

Giorgi, F., Bi, X.Q. and Pal J., 2004. Mean, interannual variability and trends in a reginal climate change experiment over Europe. II: climate change scenarios (2071-2100). Climate Dynamics 23(7-8): 839-858.

Goikoetxea, N., Borja, Á., Fontán, A., González, M. and Valencia, V., 2009. Trends and anomalies in sea-surface temperature, observed over the last 60 years, within the southeastern Bay of Biscay. Continental Shelf Research 29:1060-1069.

González, M., Mader, J., Fontán, A., Uriarte, A. and Ferrer, L., 2008a. Análisis de la tendencia de la temperatura superficial del agua en Donostia-San Sebastián, a partir del estudio de la serie del Aquarium (1946-2007). Revista de Investigación marina 4: 7 pp.

González, M., Mader, J., Fontán, A., Uriarte, Ad., Del Campo A., Ferrer, L. y Revilla, M. 2008b. Análisis de la tendencia de la temperatura atmosférica en Donostia-San Sebastián a partir del estudio de la serie del Observatorio del Monte Igeldo (1928-2007). Revista de Investigación Marina 7: 7 pp.

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IPCC, 2007. Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, Pachauri, R.K and Reisinger, A. (eds.)]. IPCC, Geneva, Switzerland, 104 pp.

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Ministerio de Medio Ambiente, 2007. El cambio climático en España. Estado de situación 2007. Unpublished report, 50 pp.

Koutsikopoulos, C., Beillois, P., Leroy, C. and Taillefer, F., 1998. Temporal trends and spatial structures of the sea surface temperature in the Bay of Biscay. Oceanologica Acta 21: 335-344.

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Southward, A.J., 1995. The importance of long time series in understanding the variability of natural systems. Helgoländer Meeresuntersuchungen 49: 329-333.

Trenberth, K.E., P.D. Jones, P. Ambenje, R. Bojariu, D. Easterling, A. Klein Tank, D. Parker, F. Rahimzadeh, J.A. Renwick, M. Rusticucci, B. Soden and P. Zhai, 2007: Observations: Surface and Atmospheric Climate Change. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Valencia, V., Borja, A., Fontán, A., Pérez, F.F. and Ríos, A.F., 2003. Temperature and salinity fluctuations in the Basque Coast (SE Bay of Biscay) from 1986 to 2000 related to the climatic factors. ICES Marine Science Symposia 219 : 340–342.

Valencia, V., Franco, J., Borja, Á. and Fontán, A., 2004. Hydrography of the southeastern Bay of Biscay. In: Borja, A., Collins, M. (eds.), Oceanography and Marine Environment of the Basque Country. Elsevier Oceanography Series, vol. 70. Elsevier, Amsterdam, pp. 159–194.

ABSTRACT

The Prestige oil spill on November 2002 affected many coastal areas of the NW Iberian Peninsula. At the Galician coast, many rocky intertidal areas were strongly impacted and large amounts of fuel

reached there. The temporal evolution of intertidal polychaete assemblages inhabiting mussel and algal beds at natural intertidal rocky shores were studied in one affected location of the western Galician coast (Caldebarcos) and compared to the temporal trends at one control location (O Segaño, Ría de Ferrol), from winter 2004 to summer 2005. Values of univariate parameters (number of species, abundance, Shannon-Wiener’s diversity) and multivariate analyses did not suggest a strong effect on the temporal variability in the composition of assemblages or abundance of taxa. Nevertheless, the lack of baseline data prevents from a full assessment of the impact and the eventual recovery of the polychaete assemblages. In addition, effects of chronic anthropogenic disturbances occurring along the Galician coast and rias might overlap with those of the Prestige oil spill according to the trends in temporal evolution observed at the control location.


33

TEMPORAL EVOLUTION OF POLYCHAETE ASSEMBLAGES ON INTERTIDAL HARD SUBSTRATA AT TWO LOCALITIES OF

THE GALICIAN COAST AFTER THE ‘PRESTIGE’ OIL SPILL

(1) Estación de Bioloxía Mariña da Graña,Universidade de Santiago de Compostela, Casa do Hórreo, Rúa da Ribeira 1, E-15590, A Graña, Ferrol, Spain.

(2) Departamento de Zooloxía e Antropoloxía Física,Universidade de Santiago de Compostela, Campus Sur,E-15782, Santiago de Compostela, Spain.

(3) Instituto de Acuicultura,Universidade de Santiago de Compostela, Campus Sur,E-15782, Santiago de Compostela, Spain.

e-mail: [email protected]

Key words: Prestige oil spill; Polychaeta; assemblages; intertidal; Galicia; Iberian Peninsula; Atlantic Ocean

XANDRO GARCÍA-REGUEIRA(1), RAMIRO TATO(1), JUAN MOREIRA(1) & VICTORIANO URGORRI(1,2,3)

34

XANDRO GARCÍA-REGUEIRA, RAMIRO TATO, JUAN MOREIRA & VICTORIANO URGORRI

INTRODUCTION

Oil spills over recent decades have become a major source of pollution in the seas across the world; those spills have, in general, negative effects on marine life (e.g. Jewett et al., 1999; Dauvin, 2000). The oil tanker Prestige sunk off the Galician coast on November 2002 after releasing to the marine environment more than 10000 tons of fuel (Junoy et al., 2005). This spill constituted the worst shipping disaster off Spain (Junoy et al., 2005) and the fuel affected both intertidal, subtidal and bathyal habitats along the Galician coast (Junoy et al., 2005; Sánchez et al., 2006; Serrano et al., 2006), also reaching other Spanish, French and Portuguese shores (García-Soto, 2004). The high heterogeneity of the Galician coast, comprising extensive rocky intertidal habitats, sandy beaches and mudflats, made it difficult to evaluate in first instance the scope of the impact of the spill (DelValls, 2003). In addition, the lack of previous studies about the biodiversity of many rocky intertidal areas added up to the aforementioned situation.

Benthic assemblages have traditionally been the subject of monitoring studies to detect changes in the environment because of their life span, response to perturbations and their sedentary or sessile nature (Bellan, 1967; Pearson & Rosenberg, 1978; Warwick, 1988; Gómez-Gesteira & Dauvin, 2005). Oil spills constitute a major source of perturbation for both intertidal and subtidal benthic assemblages (Marshall & Edgar, 2003). Benthic fauna may respond differently to these disturbances; some groups such as peracarid crustaceans are greatly affected by fuel and populations can be severely reduced (Dauvin, 1998).

Among the benthic taxa, polychaetous annelids are one of the most important groups in the coastal environment in terms of diversity, abundance and biomass (Belan, 2003) and are well-represented in the lower levels of the tidal zone in the Galician coast (Villalba & Viéitez, 1985, 1988; Parapar et al., 2009). Many polychaete species have high tolerance

to pollution by organic matter, hydrocarbons and other compounds (Borja et al., 2000; Belan, 2003; Faraco & Lana, 2003); some opportunistic species are favoured by perturbations and their presence and relative abundance might be useful to interpret changes in composition and structure of benthic assemblages (Gray & Pearson, 1982; Olsgard & Gray, 1995).

In this paper, we describe the temporal evolution of the polychaete assemblages at two intertidal locations in the West coast of Galicia after the Prestige oil spill. One of these locations was strongly affected by the spill and is compared to another location which was not affected; this was done by examining values of abundance, number of species, diversity and by means of multivariate analyses. In addition, we provide the first data on composition and structure of these assemblages at three different tidal levels to serve as baseline data for forthcoming studies.


Study area

Two study sites, located in the Galician coast (NW Spain), were selected for this study: Punta de Caldebarcos (CA; 42°50 47´ N, 009°07´52´ W), which was highly affected by the spill, and Punta do Segaño in the Ría de Ferrol (OS; 43°27´17´ N, 008°18´38´ W), which was supposedly not affected by the spill and therefore here used as control station. Both locations are exposed to oceanic swell and have extensive intertidal granitic rocky shores with a tidal range of about 3 m. Several benthic assemblages can be distinguished according to the tidal level and dominant sessile organisms in both stations: supralittoral fringe characterized by the presence of the cirripeds, Chthamalus stellatus and C. montagui; upper eulittoral fringe defined by the mussel Mytilus galloprovincialis; and lower eulittoral fringe by sessile assemblages dominated by several foliose algae, mostly Mastocarpus stellatus.

35

TEMPORAL EVOLUTION OF POLYCHAETE ASSEMBLAGES ON INTERTIDAL HARD SUBSTRATA AT TWO LOCALITIESOF THE GALICIAN COAST AFTER THE ‘Prestige’ OIL SPILL

Sampling

Quantitative sampling was done for two consecutive years (2004 and 2005) twice a year (summer and winter) at three different tidal levels at which polychaetes were present: high, corresponding to upper limit of distribution of M. galloprovincialis; middle, where M. galloprovincialis had a greater cover on the substratum; low, corresponding to the lower intertidal where algae were the dominant sessile

organisms. At each sampling date, two surfaces of 40x40 cm were scraped manually at each tidal level; samples were deposited in plastic bags and fixed in 5% buffered formalin for later sorting and identification of the polychaete fauna.

Data analysis

A matrix of abundance of species was constructed and the following univariate parameters were

Figure 1: Temporal variation in mean number of species per sample (A-C), mean number of individuals (D-F) and mean diversity (Shannon-Wiener’s index; G-

I) at each tidal level (high, middle and low) at O Segaño (control, white bars) and Caldebarcos (affected, black bars).

36


determined for each sample: total abundance (N), number of species (S) and the Shannon-Wiener’s diversity index (H’, log2). Patterns of temporal evolution in the composition of the assemblage were examined by means of multivariate analyses done through the PRIMER 6 software package (Clarke & Gorley, 2006). A similarities matrix between samples was constructed by means of the Bray-Curtis similarity index by first applying square root transformation on species abundance to downweight the contribution of the most abundant species. From the similarities matrix, samples were classified by cluster analysis based on the group-average sorting algorithm. Clusters of samples determined as statistically significant by profile test SIMPROF (alpha<0.05) were considered as having a similar polychaete composition. Non-metric multidimensional scaling (nMDS) was used to provide a visual ordination of the samples. Multivariate analyses were also done based on the similarities matrix calculated after the presence-absence data of species and based on the Sorensen similarity index.

RESULTS

A total of 33,912 polychaetes were found belonging to 104 different taxa, of which 25,640 were collected at OS (54 species) and 8,272 at CA (84 species). Syllidae and Spionidae were the most diverse families in number of species, with 23 and 10, respectively. Spirorbidae with 85.4% of the specimens collected, was by far the most abundant family being followed by Syllidae (1.6%) and Sabellidae (1.2%). Full list of taxa identified to the species/genus level is shown in Appendix I.

High tidal level

Total number of species was smaller in comparison to the other two considered tidal levels (Table 1). Total number of species and mean number of species per sample was greater in OS (13, 4) than in CA (8, 3). The families best represented were Syllidae (5 in OS; 3 in CA) and Nereididae (3, 2). Temporal evolution in

number of species was similar at both areas (Figure 1A); numbers were always smaller at CA than at OS. At the control site, maximal numbers were found in summer 2004 and winter 2005, while at CA maximal values were recorded in summer 2004. Minimal values were found in summer 2005 at both areas.

Syllids were the dominant taxa in number of individuals at both areas followed by nereidids at OS and phyllodocids at CA. Total number of individuals was greater at OS (118) than at CA (52); mean number of individuals was, in general, smaller at CA than at OS (Figure 1D). Maximal values were found in 2004 for both sampling sites; number of individuals decreased at OS by the end of the sampling period and increased slightly at CA.

Values of diversity (H’) were greater at OS during all the studied period (Figure 1G). At both sites, mean diversity increased from winter 2004 to winter 2005 and then decreased by summer 2005.

Multivariate analyses based on presence-absence and quantitative data did not reveal any significant grouping in the samples (Figures 2A-B, 3A-B). MDS ordinations showed, however, that samples from OS collected in the same year tend to be plotted close to each other.

Middle tidal level

Total number of species was greater at OS than at CA (21 vs 17). The polychaete assemblage was at both sites more diverse in number of families and species at this level than at the high level. The most diverse families were Syllidae (8 in OS; 7 in CA) and Nereididae (3, 2). Mean number of species per sample was greater in OS (8) than in CA (4); those numbers were more or less constant at OS while at CA maximal value was recorded in winter 2004 and summer 2005 and the smallest in summer 2005 (Figure 1B).

Total abundance was greater at OS (410 individuals) than at CA (86); the same pattern was

37


Figure 2: nMDS ordination of samples based on presence-absence data for each tidal level (high, A-B; middle, C-D; low, E-F) at O Segaño (A, C, E)

and Caldebarcos (B, D, F). Groups of samples determined as statiscally significant by the SIMPROF test are also shown. , winter 2004; , summer 2004; , winter 2005; , summer 2005.

38


observed for the mean number of individuals per sample. Maximal abundance was found at both sites by the end of the sampling period (summer 2005); minimal values were observed in winter (Figure 1E). Syllids and phyllodocids were the numerically dominant taxa at both sampling sites.

Diversity showed at this level the highest values in any given sample in comparison to the other two tidal levels (OS: 2.94; CA: 3.07). Mean diversity was greater at OS than at CA (Figure 1H); values were similar for all the sampling period at OS while at CA showed marked oscillations, with maximal values at winter 2004 followed by a decrease from summer 2004 to winter 2005 and a posterior increase in summer 2005.

SIMPROF analysis did not detected significant groups for samples based on presence-absence data (Figure 2C-D); nevertheless, at OS samples from the same year tend to plot together in the MDS ordination. When considering quantitative data, three different significant groups can be distinguished at OS: samples from winter 2004, those from summer 2004 and a third group composed by all samples from 2005 (Figure 3C-D). No significant groups were detected at CA.

Low tidal level

At this level, the polychaete assemblage was more diverse at CA (81 taxa) than at OS (49); mean number of species per sample was also greater at CA than at OS (22 vs 17). Syllids were the most speciose at both sampling sites (OS: 15; CA: 20), followed by Polynoidae (4 and 8, respectively), Spionidae (3, 7) and Phyllodocidae (4, 5). At OS, mean number of taxa increased trough time, showing the maximal value in winter 2005 and then decreasing in summer 2005 (Figure 1C). Values showed a seasonal pattern at CA, with maximal values in both summers and the lowest values in winter.

Total abundance showed the highest values at this tidal level; total number of individuals was

greater at OS (25,112) than at CA (8,134). Spirorbids were the dominant taxa at both sites (OS: 88%; CA: 84%), followed by syllids (3% and 7%), sabellids (4% and 2%) and nereidids (3% and 2%). At OS, mean numbers of individuals increased through 2004 and then decreased in 2005 (Figure 1F). On the contrary, at CA there was a seasonal pattern in abundance, with maximal values in summer and a posterior decrease in winter.

Mean values of diversity at OS decreased from summer to winter in both years (Figure 1I). At CA, values of diversity were more or less constant through time; maximal value (1.45) was smaller than that recorded at OS (1.90).

Multivariate analyses based on presence-absence data showed that there were two significant groups of samples at OS: that composed by samples from 2004 and another one comprised of those from 2005 (Figure 2E-F). Samples from CA showed a similar pattern; in this case the group corresponding to 2004 also included a sample from summer 2005. Quantitative analyses determined three significant groups for OS: samples from 2005, samples from summer 2004 and another group composed by samples from winter 2004 (Figure 3E-F). There were no significant groups for samples from CA.

DISCUSSION

The Prestige oil spill affected many marine habitats along the Galician coast, from the intertidal areas to bathyal depths (Junoy et al., 2005; Serrano et al., 2006). Abundance of many species decreased in the impacted areas such as those of some decapods, fishes and birds (Sánchez et al., 2006; Martínez-Abraín et al., 2006); in some cases, recovery of populations were observed the year after the spill (Sánchez et al., 2006). On the other hand, plankton dynamics were not altered in the short term by the spill (Varela et al., 2006) and the small differences found could be caused by phenomena of natural variability. Nevertheless, intertidal habitats on hard and soft bottoms were strongly affected and

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Figure 3: nMDS ordination of samples based on quantitative data for each tidal level (high, A-B; middle, C-D; low, E-F) at O Segaño (A, C, E)

and Caldebarcos (B, D, F). Groups of samples determined as statiscally significant by the SIMPROF test are also shown. , winter 2004; , summer 2004; , winter 2005; , summer 2005.

40


large quantities of fuel reached the Galician shores. In addition, cleaning activities also greatly affected those intertidal habitats (Junoy et al., 2005; Rodríguez et al., 2007), i.e. there was a decrease in populations of some polychaetes and isopods. Studies done on intertidal sediments after the spill pointed out that macrofaunal assemblages also showed differences before-after the spill (de la Huz et al., 2005; Junoy et al., 2005).

In the case of rocky intertidal habitats, many areas were covered by the fuel after the spill including one of the locations studied here, i.e. Caldebarcos. Nevertheless, our results showed that the polychaete assemblage seemed not to be greatly affected by the spill. In fact, total number of species was greater at the affected location than at O Segaño, which did not receive fuel from the spill. At the high tidal level

20

Table 1: Relative abundance (%) and total number of taxa (in brackets) of the polychaete

families present at each tidal level adding up all the samples from 2004 and 2005 for each

location. OS, O Segaño (control); CA, Caldebarcos (affected); S, total number of species.

High Middle Low OS CA OS CA OS CA

Family

Arenicolidae 0.5 (1) 0.4 (2) 0.2 (2)

Capitellidae 0.2 (1)

Cirratulidae 24.0 (2) 19.8 (1) 1.2 (1) 0.2 (4) 0.4 (6)

Eunicidae <0.1 (3)

Hesionidae <0.1 (2)

Lumbrineridae 2.3 (2) <0.1 (1) 0.6 (3)

Maldanidae <0.1 (1)

Nereididae 25.0 (3) 11.5 (2) 8.8 (3) 8.1 (2) 2.8 (3) 2.0 (5)

Opheliidae 0.1 (1)

Orbiniidae 0.1 (3)

Pholoidae <0.1 (1) 0.4 (1)

Phyllodocidae 2.5 (1) 40.4 (2) 26.6 (2) 48.9 (1) 0.5 (4) 0.3 (5)

Polynoidae 1.7 (1) 5.8 (1) 0.9 (2) 2.3 (1) 0.2 (4) 0.3 (8)

Sabellariidae 0.2 (1) <0.1 (2) 0.1 (2)

Sabellidae 3.4 (2) 4.0 (3) 2.3 (3)

Serpulidae <0.1 (2) 0.1 (2)

Sigalionidae 0.1 (3)

Syllidae 46.0 (5) 42.3 (3) 39.0 (8) 31.5 (7) 2.9 (15) 6.9 (20)

Spionidae 0.7 (1) 2.3 (1) 0.4 (3) 1.6 (7)

Spirorbidae 1.0 (1) 88.1 (1) 84.0 (1)

Terebellidae 0.8 (1) 2.5 (1) 0.1 (3) <0.1 (2)

S (total) 13 8 21 17 49 80

Table 1: Relative abundance (%) and total number of taxa (in brackets) of the polychaete families present at each tidal level

adding up all the samples from 2004 and 2005 for each location. OS, O Segaño (control); CA, Caldebarcos (affected);S, total number of species.

41


considered here, number of species and diversity were, however, greater at O Segaño than at Caldebarcos but at the end of the period of study mean number of species, abundance and diversity was similar for both locations. In general, the assemblage at both locations was dominated by “errant” families such as syllids, nereidids and phyllodocids (cfr. Table 1). Similarly, studies done on macroalgal assemblages at lowshore along the Galician coast after the spill did not show any significant change in composition of assemblages and abundance of taxa and did not detect proliferation of opportunistic species (Lobón et al., 2008). In many cases, the inmediate effects of the spill translate in loss of diversity, decrease in abundance of many taxa and an increase of species which take advantage of the lack of competitors. The overall situation suggests that the impact on the intertidal assemblage at low tidal levels was not so strong as, perhaps, in higher levels where, in addition, aggresive cleaning methods were used in many areas to wash the fuel away; those methods have usually a greater impact on the assemblages than the oil spill (Le Hir & Hily, 2002). Methods using pressurized sea water not only eliminate the fuel but also most of the sessile assemblage, i.e., barnacles, algae and mussels; this might make more difficult for new colonizing organisms to settle there. For example, the presence of barnacles provides refuge at highshore to the periwinkle, Melaraphe neritoides, whether the former are alive or dead (Le Hir & Hily, 2002); removal of the barnacle cover prevents the settlement and the survival of the periwinkle, this way delaying the recovery of their populations.

Multivariate analyses did not show, in general, any clear temporal trend between years for samples from Caldebarcos at the three studied tidal levels. At O Segaño, there were, however, differences among samples from 2004 and 2005 mostly at lowshore. This fact might be due to changes induced by the construction of the jetty of the outer harbour at the mouth of the Ría de Ferrol a few years prior to the Prestige oil spill. It is likely that the presence of this jetty could have changed the hydrodynamism at the mouth of the ria and therefore this could have translated

in changes in composition of assemblages during the last years. In fact, the cover of the substratum at low tidal levels by the alga Corallina officinalis decreased from 2004 to 2005 while that of Mastocarpus stellatus increased (authors’ unpublished data); the former is a typical species from semi-exposed and exposed rocky shores and may be affected by human perturbations (Menconi et al., 1999; Le Hir & Hily, 2002) such as those derived from changes in hydrodynamism.

Nevertheless, there was a lack of quantitative data on abundance of benthic species and composition of intertidal assemblages on rocky substrata for many areas of the Galician coast which were impacted by the Prestige oil spill, including the two locations studied here. Indeed, baseline data are needed in order to differentiate the variability of the natural systems in normal conditions from that due to the very impact of the spill and to evaluate the eventual recovery of the assemblages and populations (Lobón et al., 2008; Veiga et al., 2009). In our case, although the overall situation for the affected location suggest a normal situation or, at least, a recovery of the polychaete assemblage, the lack of previous data from the affected areas prevents a full assessment of the possible impact of the Prestige oil spill. In addition, it should be taken into account that many areas of the Galician coast are regularly affected by a number of human activities such as sewage disposal, small spills due to ship cleaning, dredging and construction of breakwaters (Alejo & Vilas, 1987; López-Jamar & Mejuto, 1988); these disturbances might induce chronic alterations on the assemblages by increase of pollutants, organic enrichment and alteration of current dynamics and their effects may overlap to those of the oil spills, as it has been pointed out for estuarine areas in Cantabria, N Iberian Peninsula (Puente et al., 2009). For instance, the changes observed in the assemblage at O Segaño during the studied period could be related to the construction of the outer harbour. In conclusion, long-term monitoring in areas susceptible to be affected by further oil spills is needed to properly separate their effects from those related to other perturbations.

42


ACKNOWLEDGEMENTS

The authors want to express their gratitude to all colleagues who collaborated in the field work and the sorting of the samples at the laboratory. Two anonymous referees provided valuable comments which contributed to greatly improve the final version of the manuscript.

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Le Hir M, Hily C (2002). First observations in a high rocky-shore community after the Erika oil spill (December 1999, Brittany, France). Marine Pollution Bulletin 44: 1243-1252.

Lobón CM, Fernández C, Arrontes J, Rico JM, Acuña JL, Anadón R, Monteoliva JA (2008). Effects of the “Prestige” oil spill on macroalgal assemblages: Large-scale comparison. Marine Pollution Bulletin 56: 1192-1200.

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Warwick RM (1988). The level of taxonomic discrimination required to detect pollution effects on marine benthic communities. Marine Pollution Bulletin 19: 259-268.

APPENDIX I

List of polychaete species found at Caldebarcos and/or O Segaño.

Class POLYCHAETAOrder PHYLLODOCIDA

Family Phyllodocidae Örsted, 1843

Eteone picta Quatrefages, 1866Eteone sp.Eulalia aurea Gravier, 1896Eumida sanguinea (Örsted, 1843)Nereiphylla parietti Blainville, 1828Phyllodoce laminosa Lamarck, 1818

Family Hesionidae Grube, 1850Psamathe fusca Johnston, 1836Syllidia armata Quatrefages, 1866

43


Family Nereididae Savigny, 1822Eunereis longissima (Johnston, 1840)Nereis pelagica Linnaeus, 1758Perinereis cultrifera (Grube, 1840)Perinereis oliveirae (Horst, 1889)Platynereis dumerilii (Audouin & Milne-Edwards, 1833)

Family Syllidae Grube, 1850Exogone naidina Örsted, 1845Odontosyllis ctenostoma Claparède 1868Salvatoria clavata (Claparède, 1863)Sphaerosyllis histrix Claparède 1863Sphaerosyllis pirifera Claparède 1868Syllides edentatus Westheide, 1974Syllis alternata Moore 1908Syllis amica Quatrefages, 1865Syllis armillaris (O.F. Müller, 1771)Syllis columbretensis (Campoy, 1982)Syllis corallicola Verrill, 1900Syllis gerlachi (Hartmann-Schröder, 1960)Syllis gracilis Grube, 1840Syllis kabilica Ben-Eliahu, 1977Syllis krohni Ehlers, 1864Syllis pectinans Haswell, 1920Syllis prolifera Krohn, 1852Syllis variegata Grube, 1860Syllis vivipara Krohn, 1869

Family Polynoidae Malmgren, 1867Harmothoe areolata (Grube, 1860)Harmothoe cf. antilopes McIntosh, 1876Harmothoe sp.Lepidonotus clava (Montagu, 1808)Malmgreniella sp.

Family Pholoidae Kinberg, 1858Pholoe synophtalmica Claparède 1868

Family Sigalionidae Malmgren, 1857Sthenelais boa (Johnston, 1839)

Order EUNICIDAFamily Eunicidae Savigny, 1818

Eunice harassii Audouin & Milne-Edwards, 1834

Lysidice ninetta Audouin & Milne-Edwards, 1833

Family Lumbrineridae Schmarda, 1861Lumbrinereis coccinea (Renier, 1804)Lumbrineris gracilis (Ehlers, 1868)Scoletoma funchalensis (Kinberg, 1865)Scoletoma impatiens (Claparède, 1868)

Order ORBINIDAFamily Orbiniidae Hartman, 1942

Phylo norvegicus (M. Sars in G.O. Sars, 1872)Protoaricia oerstedii (Claparède, 1864)

Order SPIONIDA Family Spionidae Grube, 1850

Aonides oxycephala (Sars, 1862)Dipolydora giardi (Mesnil, 1896)Malacoceros girardi (Quatrefages, 1843)Polydora caeca (Örsted, 1879)Polydora hoplura Claparède, 1869Scolelepis tridentata (Southern, 1914)

Order CIRRATULIDAFamily Cirratulidae Ryckholdt, 1851

Aphelochaeta marioni (de Saint Joseph, 1894)Caulleriella bioculata (Keferstein, 1862)Cirratulus cirratus (O.F. Müller, 1776)Cirriformia tentaculata (Montagu, 1808)Dodecaceria concharum Örsted, 1843

Order OPHELIIDAFamily Opheliidae Malmgren, 1867

Polyophthalmus pictus (Dujardin, 1839)

Order CAPITELLIDAFamily Capitellidae Grube, 1862

Capitella capitata (Fabricius, 1780)

Family Arenicolidae Johnston, 1835Arenicolides ecaudata (Johnston, 1835)Branchiomaldane vincenti Langerhans, 1881

Order TEREBELLIDA Family Sabellariidae Johnston, 1865

44


Sabellaria alveolata (Linnaeus, 1767)Sabellaria spinulosa Leuckart, 1849

Family Terebellidae Malmgren, 1867Amphitritides gracilis (Grube, 1860)Nicolea venustula (Montagu, 1818)Terebella lapidaria Linnaeus, 1767

Order SABELLIDA Family Sabellidae Malmgren, 1866

Amphiglena mediterranea (Leydig, 1851)Branchiomma lucullana (Delle Chiaje, 1828)Fabricia sabella (Ehrenberg, 1836)

Family Serpulidae Johnston,1865Pomatoceros lamarcki (Quatrefages, 1865)Pomatoceros triqueter (Linnaeus, 1767)

Family Spirorbidae Pillai, 1970Spirorbis sp.

45


REMARKS ON THE GENUS TROPHON (S.L.) MONTFORT, 1810 (MOLLUSCA: GASTROPODA: MURICIDAE)

IN THE SOUTHERN OCEAN AND ADJACENT AREAS

ABSTRACT

Among the several groups of molluscs in the southern hemisphere, the genus Trophon Montfort, 1810 has a particular importance, because it is a highly diversified taxon in the Southern Ocean and Sub-Antarctic waters. In the middle of the XX century, 27 species were known, which increased to 33 species at the beginning of the XXI century, but more than 100 species were described under this genus along the time, most of them being synonyms or belonging to other genera at the moment. Despite the great diversification

of this genus, no summarizing data from these areas are known and some records are confused by using of combining genera/subgenera (i.e. Coronium Simone, 1996, Pagodula Monterosato, 1884, Nodulotrophon Habe & Ito, 1965 and Fuegotrophon Powell, 1951). In this work we gathered data of the distribution, shell morphology and taxonomic remarks of 46 species of Trophon (s.l.) starting from a performed database with all records toward the pole from about 20ºS in South-American waters, and from about 45ºS in the Eastern Atlantic, Indian and Western Pacific Oceans. Seventeen species were found inhabiting exclusively in South-America, three in Antarctica, five in Western Sub-Antarctic waters, and five in Eastern Sub-Antarctic waters; 16 species presented a wide range of distribution. Bathymetrically, 22 species were exclusive of the continental shelf, 23 reached the slope and one the deep-sea (>3,000 m). From the shell morphology, five main morphotypes were recognized. Affinities between species and with combining genera were discussed from the obtained data.

(1) Departamento de Ecología y Biología Animal,Facultad de Ciencias del Mar.Campus Lagoas Marcosende, 36310.Universidad de Vigo, ESPAÑA.E-mail: [email protected] (C. Aldea), [email protected]

(2) Fundación Centro de Estudios del Cuaternario de Fuego-Patagonia y Antártica (CEQUA), Avenida Bulnes 01890, Punta Arenas, CHILE.


Key words: Trophon, distribution, bathymetry, morphology, Antarctica, South-America, Sub-Antarctic islands.

CRISTIAN ALDEA(1,2) & JESÚS S. TRONCOSO(1)

47

48

CRISTIAN ALDEA & JESÚS S. TRONCOSO

Fig.�1/10

Figure 1: Distribution of species of Trophon (s.l.) in South-America: T. acanthodes (ac), T. amettei (am), T. bahamondei (ba), T.

columbarioides (cb), T. ceciliae (ce), T. clenchi (cl), T. condei (co), T. declinans (de), T. fasciolarioides (fa), T. geversianus (ge), T. iarae (ia), “T.” malvinarum (ma), T. minutus (mi), T. ohlini (oh), T. pallidus (pa), T. pelseneeri (pe), T. plicatus (pl), T. parodizi

(pr), T. patagonicus (pt), T. triacanthus (tr), T. vangoethemi (va) and T. veronicae (ve).

49

REMARKS ON THE GENUS TROPHON (S.L.) MONTFORT, 1810 (MOLLUSCA: GASTROPODA: MURICIDAE)IN THE SOUTHERN OCEAN AND ADJACENT AREAS

INTRODUCTION

The genus Trophon Montfort, 1810 represents particular importance among the several genera of molluscs in the southern hemisphere since it has a high diversification, mainly in the Southern Ocean and adjacent waters. The austral origin, being the older species traced as far back as the Oligocene (Griffin and Pastorino, 2005), and

the morphologic pattern with all fusiform and/or lamellate –usually with spiral ornamentation– muricids (Pastorino and Scarabino, 2008) are highlighted points of shell morphology in the identity of this genus.

From the proposal of the genus for Buccinum geversianus Pallas, 1774, numerous records with taxonomic remarks and new species from research

Fig.�2/10

Figure 2: Distribution of species of Trophon (s.l.) around Antarctica: T. coulmanensis coulmanensis (cc), T. coulmanensis multilamellatus (cm), T. cuspidarioides (cu), T. drygalskii (dr), T. echinolamellatus (ec), T. enderbyensis (en), T. leptocharteres (le), T. longstaffi (lo), T. minutus (mi), T. nucelliformis (nu), T. poirieria (po), T. shackletoni paucilamellatus (sp), T. shackletoni shackletoni (ss)

and T. scotianus (st).

50


expeditions were published (e.g. Rochebrune and Mabille, 1889; Strebel, 1908; Powell, 1951; Powell, 1958), giving a first account of 27 species by Powell (1960). Later on, new records and new

species have been noticed (e.g. McLean and Andrade, 1982; Dell, 1990; Numanami, 1996; Houart, 1997), considering morphological aspects, but regardless of their real affinities.

Fig.�3/10

Figure 3: Distribution of species of Trophon (s.l.) in western Sub-Antarctica: T. acanthodes (ac), T. albolabratus (al), T. arnaudi (ar), T.

brevispira (br), T. coulmanensis coulmanensis (cc), T. cribellum (cr), T. cuspidarioides (cu), T. distantelamellatus (di), T. drygalskii (dr), T. echinolamellatus (ec), T. emilyae (em), T. leptocharteres (le), T. longstaffi (lo), T. minutus (mi), T. nucelliformis (nu), T.

shackletoni paucilamellatus (sp), T. shackletoni shackletoni (ss) and T. scotianus (st).

51


Then Pastorino (2002a) revised the morphological patterns of the systematics and phylogeny of the genus in Patagonia and Antarctica, pointing out the existence of 33

species from more than 100 proposed species names under the genus for South America and Antarctica, many of which are now junior synonyms or belong to other genera (i.e. Xymenopsis Powell, 1951). The

Fig.�4/10

Figure 4: Distribution of species of Trophon (s.l.) in eastern Sub-Antarctica: T. albolabratus (al), T. coulmanensis coulmanensis (cc), T.

declinans (de), T. eversoni (ev), T. geversianus (ge), T. macquariensis (mc), T. minutus (mi), T. mawsoni (mw), T. pallidus (pa), T. scolopax (sc), T. septus (se) and T. shackletoni shackletoni (ss)..

52


same author (Pastorino, 2005) developed a review of all living species from both coasts of southern South America, involving those taxa living in environments associated with the continental shelf, but not considering deeper water species.

The last works known on the genus are the review of the last described species of Trophoninae from Chilean waters (Houart and Sellanes, 2006) and the description of two species from Argentinean deep-sea by Pastorino and Scarabino (2008).

Fig.�5/10

Figure 5: Bathymetry of species of Trophon (s.l.). Three bathymetric boundaries were marked at 400 m, 800 m and 3,000 m; in brackets the

depth range of the species; species with large distribution with black bars. T. acanthodes (ac), T. albolabratus (al), T. amettei (am), T. arnaudi (ar), T. bahamondei (ba), T. brevispira (br), T. columbarioides (cb), T. coulmanensis coulmanensis (cc), T. ceciliae (ce), T. clenchi (cl), T. coulmanensis multilamellatus (cm), T. condei (co), T. cribellum (cr), T. cuspidarioides (cu), T. declinans

(de), T. distantelamellatus (di), T. drygalskii (dr), T. echinolamellatus (ec), T. emilyae (em), T. enderbyensis (en), T. eversoni (ev), T. fasciolarioides (fa), T. geversianus (ge), T. iarae (ia), T. leptocharteres (le), T. longstaffi (lo), “T.” malvinarum (ma), T.

macquariensis (mc), T. minutus (mi), T. mawsoni (mw), T. nucelliformis (nu), T. ohlini (oh), T. pallidus (pa), T. pelseneeri (pe), T. plicatus (pl), T. poirieria (po), T. parodizi (pr), T. patagonicus (pt), T. scolopax (sc), T. septus (se), T. shackletoni paucilamellatus

(sp), T. shackletoni shackletoni (ss), T. scotianus (st), T. triacanthus (tr), T. vangoethemi (va) and T. veronicae (ve).

53


Despite the extensive information existing at the present time, no summarizing data are available mainly in the Antarctic and East Sub-Antarctic areas and some records are confused by using combining genera/subgenera (i.e. Coronium Simone 1996, Pagodula Monterosato, 1884 and Fuegotrophon Powell, 1951). Therefore, the aim of this paper is to gather the scattered literature of all Trophon (s.l.) species in the Southern Ocean and adjacent areas, standing out the morphology of the shell and geographical, bathymetrical and some systematics aspects to help to the identification of the species.


A complete database with about 700 records of Trophon (s.l.) and related genus (Coronium and Pagodula) of species distributed in the Southern Ocean and adjacent areas was performed. Concretely, those records toward the pole from about 20ºS in the western Atlantic Ocean and eastern Pacific Ocean –South America–, and from about 45ºS in the eastern Atlantic, Indian and western Pacific Oceans were considered. The database included the geographic location, bathymetry, and some taxonomic remarks of all records of the species of the genus found in the literature and in the National Collection of the Smithsonian National Museum of Natural History, USNM, available in Internet (http://invertebrates.si.edu/, accessed in March, 15th, 2009).

Data were processed geographically and bathymetrically to characterize the species by their distributions. The bathymetrical boundaries were established following Aldea et al. (2008). For each species, taxonomic remarks and morphological information of the shell were processed, and images or draws of representative specimens were redrawn to point out the main conchological features and to split the species in morphological groups. A dichotomic key for all species was performed by means of the division of the groups and using the terminology given in the original descriptions of the species or subsequent revisions for the sculpture.

RESULTS

Distribution and bathymetry

Forty-six species of the genus Trophon (s.l.) were found (Table 1) inhabiting in the study area. Twenty-two species were distributed in South America (Fig. 1), of which 17 species presented an exclusive South-American distribution (T. amettei, T. bahamondei, T. ceciliae, T. clenchi, T. columbarioides, T. condei, T. fasciolarioides, T. iarae, “T.” malvinarum, T. ohlini, T. parodizi, T. patagonicus, T. pelseneeri, T. plicatus, T. triacanthus, T. vangoethemi and T. veronicae). Fourteen species were found in Antarctic waters (Fig. 2), from which three are exclusive from there (T. coulmanensis multilamellatus, T. enderbyensis and T. poirieria). Eighteen species are from western Sub-Antarctic islands and waters (Fig. 3), five of which being endemic from there (T. arnaudi, T. brevispira, T. cribellum, T. distantelamellatus and T. emilyae). Twelve species are from eastern Sub-Antarctic waters (Fig. 4), five from which being endemic from there (T. eversoni, T. macquariensis, T. mawsoni, T. scolopax and T. septus).

Sixteen species have a distribution that exceeded the limits established here: T. acanthodes, T. geversianus and T. pallidus have a large South-American distribution (Fig. 1), but the first reaches western Sub-Antarctic waters (Fig. 3) while T. geversianus and T. pallidus were found in eastern Sub-Antarctic islands (Fig. 4); T. coulmanensis coulmanensis, T. drygalskii, T. longstaffi, T. minutus, T. scotianus and T. shackletoni shackletoni have a circum-Antarctic distribution (Fig. 2) that reaches the western Sub-Antarctic waters (Fig. 3), while T. minutus also reaches South-America (Fig. 1) and eastern Sub-Antarctic waters (Fig. 4) and T. coulmanensis coulmanensis and T. shackletoni shackletoni also reach eastern Sub-Antarctic waters (Fig. 4); T. cuspidarioides, T. echinolamellatus, T. leptocharteres, T. nucelliformis and T. shackletoni paucilamellatus are species shared between the West Antarctica (Fig. 2) and western Sub-Antarctic waters (Fig. 3); T. albolabratus and T.

54


declinans are species from eastern Sub-Antarctic waters (Fig. 4), being the first found in the western Sub-Antarctic islands (Fig. 3) as well and the second in the waters of South-America (Fig. 1).

In terms of vertical distribution (Fig. 5), 22 species had a distribution above 400 m depth, being been able to consider them as exclusive of the continental shelf, 10 species reached the upper slope zone and 13

species the lower slope (above 800 and 3,000 m depth, respectively), and one species (T. shackletoni shackletoni) reached the deep-sea (below 3,000 m depth).

External morphology and dichotomic key

Five main morphotypes were recognized: (a) fusiform shells of rounded shape with rounded –or

A

rr rr

rrwc

lc

lc

c

rll

l

l

l

l

l

lc

bc

c

gs

B

CD

E

F

G

H

I

Fig.�6/10

Figure 6: Redraws of Trophon (s.l.) species: A, T. parodizi, paratype from Pastorino (2005), 21.1 x 10.6 mm; B, T. minutus, holotype from Melvill and Standen (1907), 7.3 x 4.0 mm; C, T. pallidus, specimen from Strebel (1908), 27.1 x 12.9 mm; D, T. condei, holotype from Houart (2003), 61.4 x 27.7 mm; E, T. macquariensis, USNM 886110, 19.6 x 9.3 mm; F, T. declinans, from Watson (1886),

20.3 x 8.1 mm; G, T. emilyae, holotype from Pastorino (2002b), 12.1 x 3.2 mm; H, T. cuspidarioides, holotype from Powell (1951), 13.0 x 5.7 mm; I, T. fasciolarioides, holotype from Pastorino and Scarabino (2008), 11.2 x 4.8 mm; bc, blunt cord; c, cord; gs,

growth stria; l, lamella; lc, low cord; rr, rounded ridge; rl, rolled lamella; wc, weak cord.

55


weakly angulose– shoulders and external lip, and siphonal canal variable in length (Fig. 6); (b) fusiform shells of angulated shape with angulose shoulders and external lip, and a long (about 25–43% total shell length) almost straight or curved strong siphonal canal (Fig. 7), or (c) short to medium (about 13–23% total shell length) siphonal canal (Fig. 8); (d) oval shells with a short to medium siphonal canal (Fig. 9) or (e) with a long, thin and brittle prolonged siphonal canal and long and straight open abaxial spines along the shoulders (Fig. 10).

(1) Fusiform shells of rounded shape with rounded –or weakly angulose– shoulders and external lip (Fig. 6)

(2)

(1’) Shells with other shape: fusiform shells of angulated shape or oval shells

(10)

(2) Axial sculpture with lamellae and/or growth striae

(3)

(2’) Axial sculpture only of irregular and low rounded ridges.

T. parodizi Pastorino, 2005 (Fig. 6A)

AB

C

D

E

F G

l

ll

t

l

c

wc

ll

lc

os

os

os

os

os

Fig.�7/10

Figure 7: Redraws of Trophon (s.l.) species: A, T. acanthodes, from Watson (1886), 38.1 x 16.3 mm; B, T. columbarioides, holotype from

Pastorino and Scarabino (2008), 14.7 x 8.4 mm; C, T. septus, from Watson (1886), 23.1 x 10.9 mm; D, T. vangoethemi, holotype from Houart (2003), 16.9 x 7.9 mm; E, T. veronicae, holotype from Pastorino (1999), 52.2 x 19.6 mm; F, T. arnaudi, holotype

from Pastorino (2002b), 11.0 x 5.8 mm; G, T. scolopax, from Watson (1886), 24.1 x 10.7 mm; c, cord; l, lamella; os, open spine; t, thread; wc, weak cord.

56


(3) Siphonal canal medium to long and no strong axial lamellae adaperturally rolled

(4)

(3’) Siphonal canal short and axial lamellae adaperturally rolled. Some specimens can be more shouldered. T. minutus Strebel, MS. Melvill and Standen, 1907 (Fig. 6B)

(4) Axial rounded ribs with lamellae (5)

(4’) Without axial rounded ribs, only lamellae or growth striae

(7)

(5) Few axial lamellae located on top of the ribs crossing low, almost obsolete, spiral cords

(6)

(5’) Many axial lamellae arranged tightly, crossing narrow and strong spiral cords and forming reticulate sculpture.

T. pallidus (Broderip, 1833) (Fig. 6C)

(6) The lamellae are weak and the aperture is expanded.

T. condei Houart, 2003 (Fig. 6D)

(6’) The lamellae tend to be strong and the aperture is not expanded.

T. macquariensis Powell, 1957 (Fig. 6E)

(7) Lamellae clearly visible and they are arranged in order

(8)

(7’) Very weak lamellae that are not arranged in order, or growth striae

(9)

(8) Protruding lamellae and without spiral sculpture.

T. declinans Watson 1882 (Fig. 6F)

(8’) Not protruding lamellae and low rounded spiral cords.

T. emilyae Pastorino, 2002 (Fig. 6G)

(9) Weak lamellae crossing a few blunt spiral cords.T. cuspidarioides Powell, 1951 (Fig. 6H)

(9’)Growth striae crossing many rounded and well defined spiral cords.

T. fasciolarioides Pastorino and Scarabino, 2008 (Fig. 6I)

(10) Fusiform shells of angulated shape with angulose shoulders and external lip (Figs. 7 and 8)

(11)

(10’) Oval shells (31)

(11) Long (about 25–43% total shell length) almost straight or curved strong siphonal canal (Fig. 7)

(12)

(11’) Short to medium (about 13–23% total shell length) siphonal canal (Fig. 8)

(18)

(12) Axial lamellae producing open spines only along the shoulders

(13)

(12’) Axial lamellae producing open spines that tend to be short –or spine-like expansions– along the spiral sculpture or weak projections along the periphery when crossing the spirals

(16)

(13) The spines tend to be long and abaxial (14)

(13’) The spines tend to be short (or triangular) and adapical

(15)

(14) Irregular spiral cords, mainly visible at the base.

T. acanthodes Watson, 1883 (Fig. 7A)

(14’) Without spiral sculpture. T. columbarioides Pastorino and

Scarabino, 2008 (Fig. 7B)

(15) Spire low (about 28% total length) and “sub-quadrate” expanded aperture. Some specimens have weak expansions on the base.

T. septus Watson, 1882 (Fig. 7C)

(15’) Spire high (about 34% total length) and less expanded aperture.

T. vangoethemi Houart, 2003 (Fig. 7D)

(16) Lamellae that tend to produce spines; spire tending to be shorter (25–35% total length) with less that seven whorls

(17)

(16’) Weak lamellae that tend to produce weak projections along the periphery; spire tending to be higher (about 40% total shell length) with seven or more whorls.

T. veronicae Pastorino, 1999 (Fig. 7E)

(17) Four to five real spiral cords on last whorl. T. arnaudi Pastorino, 2002 (Fig. 7F)

(17’) Two to three feeble rounded threads on last whorl.

T. scolopax Watson, 1882 (Fig. 7G)

(18) Shell sculptured only by axial low varices, or spines not produced by striae neither lamellae; with spiral ribs or cords

(19)

(18’) Shell sculptured by axial lamellae or growth striae, which can produce spines; with or without spiral sculpture

(20)

(19) Low varices crossing about three spiral cords in the last whorl. Six whorls. “T.” malvinarum Strebel, 1908 (Fig. 8A)

57


(19’) Spines on periphery arranged in three spiral ribs in the last whorl. Striae at the base. Four whorls.

“T.” triacanthus Castellanos, Rolán and Bartolotta, 1987 (Fig. 8B)

(20) Spiral sculpture almost invisible, rarely present and very weak or lacking

(21)

(20’) Evident spiral sculpture of cords, ribs or threads

(26)

(21) Well defined long and open axial spines only along the shoulders, which tend to be abaxial. Spiral sculpture lacking

(22)

(21’) Axial lamellae producing open spines that tend to be adapical. Spiral sculpture lacks or very weak and rarely present

(23)

(22) The spines are connected to growth striae. T. poirieria Powell, 1951 (Fig. 8C)

(22’) The spines are connected to evident axial lamellae.

T. iarae Houart, 1998 (Fig. 8D)

(23) Relatively thick shells with lamellae that tend to be thick, attached to the shell or sometimes almost lack

(24)

(23’) Delicate shells with lamellae that tend to be thin and sharp

(25)

(24) Well defined thick lamellae that can produce open adapical curved spines along the shoulders; the lamellae being sometimes adaperturally cur-ved or sometimes almost lack. Spiral ornamentation almost invisible, some-times six weak cords at the base.

T. plicatus (Lightfoot, 1786) (Fig. 8E)

(24’) Thick lamellae that tend to be not protruding, but producing open adapical short spines along the shoulders. Lack of spiral ornamentation.

T. bahamondei McLean and Andrade, 1982 (Fig. 8F)

(25) The lamellae produce open adapical spines only along the shoulders. Spiral ornamentation of very fine striae.

T. coulmanensis coulmanensis Smith, 1907 (Fig. 8G)

(25’) The lamellae produce open adapical spines along the shoulders and the base. Spiral ornamentation unknown.

T. coulmanensis multilamellatus Numanami, 1996 (Fig. 8H)

(26) Axial lamellae crossing many spiral cords, weak ribs or threads

(27)

(26’) Many thin and tight axial lamellae crossing three thick spiral cords in the last whorl beginning at the periphery, which are more visible along the external lip.

T. drygalskii Thiele, 1912 (Fig. 8I)

(27) Axial lamellae crossing many strong cords producing knobs with short spines along the shoulders or a cancellated sculpture

(28)

(27’) Axial lamellae crossing many weak ribs or threads, only producing open spines or expansions along the shoulders

(29)

(28) Ten axial lamellae producing knobs and sometimes short open spines along the periphery.

T. ceciliae Houart, 2003 (Fig. 8J)

(28’) Up to 13 axial arranged lamellae producing a cancellate sculpture when crossing the spirals. Sometimes the lamellae producing a short expansion on the shoulder of the last whorl.T. distantelamellatus Strebel, 1908 (Fig. 8K)

(29) The axial lamellae tend to be strong and adaperturally curved, producing adapical spines or expansions along the shoulders. Spiral sculpture of tight weak threads or cords

(30)

(29’) The axial lamellae tend to be weak and shallow producing feeble expansions along the shoulders. Spiral sculpture of distant weak ribs. Some specimens can be a more rounded shape.

T. ohlini Strebel, 1904 (Fig. 8L)

(30) The expansions produced by the lamellae are rounded and concave. Spiral sculpture of 6–10 cords on lower part of the last whorl, others obsolete.

T. amettei Carcelles, 1946 (Fig. 8M)

(30’) The expansions produced by the lamellae tend to be angulose to true open spines, although some specimens can be a more rounded shape. Spiral sculpture of weak threads.

T. pelseneeri Smith, 1915 (Fig. 8N)

(31) Oval shells with siphonal canal short to medium and without long and straight open abaxial spines along the shoulders (Fig. 9)

(32)

58


(31’) Oval shell with a long, thin and brittle prolonged siphonal canal and axial lamellae (7–9) producing long and straight open abaxial spines along the shoulders (Fig. 10).

T. clenchi (Carcelles, 1953)

(32) Shells with well defined spiral sculpture of cords or ridges

(33)

(32’) Shells without spiral sculpture, missing, or very weak either spaced lines, low ridges or very fine striae

(42)

(33) Axial sculpture of regular lamellose cords crossing strong spirals cords, giving a cancellated sculpture

(34)

(33’) Axial sculpture of true lamellae, which can produce reticulation when crossing the spirals in some species

(35)

(34) Spire very low (about 24% total length) of four whorls.

T. brevispira Martens, 1885 (Fig. 9A)

(34’) Spire higher (about 36% total length) of five whorls.

T. cribellum Strebel, 1908 (Fig. 9B)

(35) Numerous axial lamellae producing reticulated sculpture when crossing conspicuous spiral cords or ridges

(36)

(35’) Axial lamellae that, being more distant, do not produce reticulation when crossing low rounded spiral cords

(40)

(36) Without expansions nor open spines along the shoulders

(37)

(36’) Expansions or adapical short open spines along the shoulders produced by axial lamellae

(39)

(37) Axial lamellae not producing sharp recurved hollow spines when crossing rounded spiral cords

(38)

(37’) Axial lamellae producing sharp recurved hollow spines when crossing flat spiral cords.T. echinolamellatus Powell, 1951 (Fig. 9C)

(38) About 46–50 axial lamellae crossing about 13–18 spirals cords.

T. albolabratus Smith, 1875 (Fig. 9D)

(38’) About 20–28 axial lamellae crossing about 17–18 spirals cords. Some half-grown specimens can present some weak expansion in lamellae.

T. mawsoni Powell, 1957 (Fig. 9E)

(39) About 8–10 well defined and regular axial lamellae crossing strong spiral cords beginning at the periphery, and producing adapical short open spines along the shoulders; whilst some specimens can vary in thickness and from almost smooth with more prominent spiral sculpture to very lamellated with weak spirals

T. geversianus (Pallas, 1774) (Fig. 9F)

(39’) About 17–22 irregular axial lamellae crossing weak spiral ridges, and sometimes producing rounded expansions along the shoulders.

T. leptocharteres Oliver and Picken, 1984 (Fig. 9G)

(40) More than six thin axial lamellae regularly spaced

(41)

(40’) With about one shallow lamellate varix in one-third whorl and a closely spaced group of three associated with the labial varix.

T. enderbyensis Powell, 1958 (Fig. 9H)

(41) About 12–13 adaperturally curved lamellae producing weak adapical rounded expansions along the shoulders in some specimens.

T. eversoni Houart, 1997 (Fig. 9I)

(41’) About 6–11 more straight lamellae producing adapical coronated processes along the shoulders.

T. scotianus Powell, 1951 (Fig. 9J)

(42) Axial ornamentation of lamellae (in some cases almost obsolete), spiral lacking, missing or very fine striae, and expanded aperture

(43)

(42’) Axial ornamentation of irregular growth striae, spiral of very weak spaced lines or low ridges in some shells, and oval less expanded aperture. T. nucelliformis Oliver and Picken, 1984

(Fig. 9K)

(43) Less than about 14 solid lamellae producing adapical spines or conspicuous expansions along the shoulders, lacking or missing spiral sculpture

(44)

(43’) About 10–27 thin lamellae sometimes producing weak sharp and rounded expansions along the shoulders. Very fine spiral striae that are rubbed off in some specimens.

T. longstaffi Smith, 1907 (Fig. 9L)

59


A B CD

EG

FH

I

J

K

L

M

N

vc

s osos

gsl

l

l

l

l

l

l

wr

cs

lc

c

c

k

l

l

l

l

os

os

fsos

os

os

c

r

Fig.�8/10

Figure 8: Redraws of Trophon (s.l.) species: A, “T.” malvinarum, from Strebel (1908), 7.2 x 3.6 mm; B, T. triacanthus, holotype from Castellanos et al. (1987), 3.1 x 2.1 mm; C, T. poirieria, holotype from Powell (1951), 15.5 x 8.8 mm; D, T. iarae, holotype

from Houart (1991), 74.6 x 61.0 mm; E, T. plicatus, from Pastorino (2005), 51.0 x 25.9 mm; F, T. bahamondei, holotype from McLean and Andrade (1982), 49.4 x 26.1 mm; G, T. coulmanensis coulmanensis, holotype from Smith (1907), 13.0 x 7.0 mm; H, T. coulmanensis multilamellatus, from Numanami (1996), 9.0 x 4.6 mm; I, T. drygalskii, from Thiele (1912), 7.0 x 3.7 mm; J, T.

ceciliae, holotype from Houart (2003), 41.5 x 21.6 mm; K, T. distantelamellatus, from Strebel (1908), 15.1 x 7.9 mm; L, T. ohlini, USNM 901764, 8.7 x 4.3 mm; M, T. amettei, holotype from Pastorino (2005), 26.8 x 13.7 mm; N, T. pelseneeri, from Strebel

(1908), 20.5 x 9.5 mm; c, cord; cs, concave spine; fs, fine stria; gs, growth stria; k, knob; lc, low cord; l, lamella; os, open spine; r, ridge; s, spine; v, varix; wr, weak rib.

60


A BC D

E F G

H

I J K L

M

N O

llc

llcl

l

l ll

os

fc

hs c

cc

r

lv

l

l

lc

lc

c

gsl

l

l

l

os

os

fs

c

c

Fig.�9/10 Figure 9: Redraws of Trophon (s.l.) species: A, T. brevispira, from Martens and Pfeffer (1886), 29.0 x 21.0 mm; B, T. cribellum, from Strebel

(1908), 17.7 x 8.8 mm; C, T. echinolamellatus, paratype from Powell (1951), 64.0 x 39.0 mm; D, T. albolabratus, from Smith (1879), 40.0 x 18.0 mm; E, T. mawsoni, USNM 896644, 27.0 x 17.0 mm; F, T. geversianus, from Pastorino (2005), 61.8 x 40.5 mm; G, T. leptocharteres, USNM 901770, 18.5 x 10.8 mm; H, T. enderbyensis, holotype from Powell (1958), 70.0 x 38.5 mm; I, T. eversoni, holotype from Houart (1997), 75.8 x 43.8 mm; J, T. scotianus, holotype from Powell (1951), 34.0 x 24.0 mm; K, T.

nucelliformis, holotype from Oliver and Picken (1984), 21.6 x 12.6 mm; L, T. longstaffi, from Smith (1907), 41.0 x 25.5 mm; M, T. patagonicus, syntype from Pastorino (2005), 54.2 x 38.4 mm; N, T. shackletoni shackletoni, from Hedley (1911), 26.0 x 18.0 mm; O, T. shackletoni paucilamellatus, holotype from Powell (1951), 31.0 x 21.0 mm; c, cord; fc, flat cord; fs, fine stria; gs, growth

stria; hs, hollow spines; l, lamella; lc, low cord; llc, lamellose cord; lv, lamellate varix; os, open spine; r, ridge.

61


(44) Axial lamellae thin but solid, producing adapical open spines that tend to be long. Lacking spiral sculpture

(45)

(44’) Axial lamellae strong producing adapical conspicuous expansions that tend to be short or in some specimens the lamellae become obsolete or lacking. Spiral sculpture missing and only present in first whorls of some specimens. T. patagonicus (d’Orbigny, 1839) (Fig. 9M)

(45) About 12–14 axial lamellae. T. shackletoni shackletoni Hedley, 1911

(Fig. 9N)

(45’) About 7–10 more prominent axial lamellae.

T. shackletoni paucilamellatus Powell, 1951 (Fig. 9O)

DISCUSSION AND CONCLUSIONS

Of the numerous well-known works for the genus Trophon in the Southern Ocean and Sub-Antarctic adjacent waters, the work of Pastorino (2005) can be considered as a true revision, which constitutes a review of all living species from both coasts of southern South America living in environments associated with the continental shelf. Other good accounts where some species were synonymized were developed by Powell (1951), focused mainly on Magellan, Sub-Antarctic and West Antarctic species, and by Dell (1990), focused mainly on Antarctic Ross Sea species, but none of both studies was a true revision. The work of Pastorino (2002a) revised the morphological patterns of the systematics and phylogeny of the genus in Patagonia and Antarctica. All fragmented information generated contrasting with the high number of species found in this work that shared distribution between Antarctic and Sub-Antarctic areas, being at the moment more viable a work of compilation to gather the scattered information and data of this genus, without taken account species distributed from median/low latitudes toward the equator (i.e., South African species and from 20ºS in South America), and starting from the aim to achieve a quick identification of the species using macroscopic conchological characters, considering

that many specimens lose the protoconch and firsts whorls. However, there are some taxonomical remarks and distributional observations important to detail.

Taxonomical remarks

Well documented species and some of them with a long list of accepted synonyms are those revised in South America by Pastorino (2005), but he did not include in his work T. mucrone Houart, 1991 (not considered here, see below) and T. veronicae since they seem to belong in a different group when more data are available, T. ohlini for resembling the boreal Boreotrophon truncatus, and T. triacanthus for belonging probably to the muricid genus Apixystus (see Pastorino, 2005, p. 55). However, Pastorino in his work included Trophon wilhelmensis Ramírez-Bohme, 1981, from off Chiloé Island, Chile, as a valid species, which later on was located under the muricid genus Coronium by Houart and Sellanes (2006) based on radular and protoconch characters; therefore, we did not consider the currently Coronium wilhelmensis in this paper. Pastorino also included “Trophon” malvinarum under dubius genus awaiting

l

c

ss

Fig.�10/10

Figure 10: Redraw of Trophon clenchi, holotype from Pastorino (2005), 52.3 x

32.8 mm; c, cord; l, lamella; ss, straight spine.

62


more data to confirm the true identity, and included T. varians (d’Orbigny, 1839) as a junior synonym of T. geversianus, but Houart (1998) figured a syntype from MNHN (Paris) that Pastorino did not list as synonym. Furthermore, there are species whose generic position is pending of definitive verification, like T. acanthodes, which possess a shell similar to south Atlantic Coronium coronatum (Penna-Neme & Leme, 1978) according Pastorino (2005), being able to belong to that genus.

T. pallidus was referred as Fuegotrophon pallidus by Pastorino (2002a), but we do not have data to consider it under that genus, which originally proposed as the subgenus Fuegotrophon by Powell (1951) based on the protoconch and radula.

Houart and Sellanes (2006) described Pagodula concepcionensis from off Concepción, Chile, and one specimen assigned as P. cf. concepcionensis, that according the same authors may be referable to T. concepcionensis (Houart and Sellanes, 2006, p. 61), but more data and specimens are necessary.

Finally, T. pileus Lamy is a doubtful species from Southwest Atlantic Ocean (55ºS, 64.8ºW) housed in USNM and not figured.

Distributional observations

In this work the geographic and bathymetric range of the species is gathered and actualized. In this sense, Pastorino (2002a) showed three groups of species arranged according to their geographical distributions: Magellanic, Circumantarctic and insular ones, and that there is no interchange between Patagonia and Antarctica species. However we found some species recorded in both areas –Magellan and Antarctica– (e.g. T. minutus) and that only three are truly Antarctic species, most species reaching insular and Sub-Antarctic areas at deeper waters.

Although a definite pattern of distribution was observed in most species, inhabiting contiguous

areas as southern South America and Sub-Antarctic areas (e.g. T. acanthodes), or high Antarctic and Sub-Antarctic islands (e.g T. drygalskii), there are some species with doubtful records (see Table 1) such as T. geversianus at Western Antarctic Peninsula and South Orkney Islands that was questioned by Pastorino (2005), or T. poirieria at South Georgia Islands, questioned by Zelaya (2005). In addition, the strongly discontinuous pattern of distribution of some species caught our attention, such as the South American T. geversianus and T. pallidus that were found at eastern Sub-Antarctic islands, and the eastern Sub-Antarctic T. albolabratus and T. declinans that were found at western Sub-Antarctic islands and in waters of South-America, respectively (see Table 1). All those records need a comparison by means of future revision works and more data –and specimens– available from intermediate areas.

Extralimital species of this study were the South American T. aculeatus Watson, 1882, from Brazil (9–23ºS), T. verrillii Bush, 1893, from Brazil (19ºS), and T. mucrone Houart, 1991, from Brazil (18–38ºS), presenting more affinity with species from the northern hemisphere (see Houart, 1991), excepting T. mucrone that presented affinity with T. ceciliae as well, that differs in having a larger and broader shell with more numerous primary spiral cords and secondary cords, which are not present in T. mucrone (Houart, 1998).

ACKNOWLEDGMENTS

This paper was generated from the data gathered and information developed starting from the Spanish cruises BENTART 2003/2006 that were carried out under the auspices of the Spanish Government through the Antarctic Programmes REN2001-1074/ANT and GLC2004-01856/ANT of the Ministry of Education and Science (MEC). We thank Linda Ward of the Department of Invertebrate Zoology, Smithsonian Institution, for kindly sending the Trophon records of USNM. We also thank two anonymous referees for improving the manuscript and Cristina Vertan for her kindly revision of the English language.

63


25

Table 1. Species of Trophon (s.l.) arranged alphabetically showing their distribution and bathymetry. Coordinates of geographic toponyms are indicated in the Appendix; USNM, Smithsonian National Museum of Natural History; n.d., no data were obtained.

Species - Distribution Bathymetry (m) and source T. acanthodes Watson, 1883 Río Grande do Sul n.d. (Rios, 1994) Off Uruguay n.d. (Pastorino, 2005) Off Punta Médanos 104–111 (Pastorino, 2005) Off Mar del Plata 192 (Pastorino, 2005) Off Bahía Blanca 82–95 (Pastorino, 2005) East of Falkland/Malvinas Islands

(56.7ºW) 855–866 (Pastorino, 2005)

Between South Georgia and South Orkney Islands (59ºS, 38ºW)

n.d. (Houart, 1998)

Tierra del Fuego Island n.d. (Pastorino, 2005) Off Desolación Island (75.3ºW) 119–319 (Pastorino, 2005) Between Manuel Rodriguez and

Desolación Islands 188–544 (Pastorino, 2005), 448 (Watson, 1886)

Wellington Island 320 (Watson, 1886) Boca del Guafo to Ninualac Channel 160–200 (Osorio et al., 2006) Gulf of Corcovado 130–169 (Cárdenas et al., 2008) T. albolabratus Smith, 1875 South Georgia Islands n.d. (Martens and Pfeffer, 1886) (1) Kerguelen Islands 0 (Smith, 1879), 0–30 (Powell, 1957), 25–50 (Troncoso et al., 2001),

0–104 (Cantera and Arnaud, 1985), 46–110 (Watson, 1886) T. amettei Carcelles, 1946 Bustamante Bay 11 (Pastorino, 2005) T. arnaudi Pastorino, 2002 South Sandwich Islands 355–468 (Pastorino, 2002b) T. bahamondei McLean and Andrade, 1982 Off Coquimbo to off Pichilemu 200–400 (McLean and Andrade, 1982) SW Coquimbo 370 (Houart, 2003) Off Coquimbo 400 (Pastorino, 2005) Gulf of Ancud to Gulf of Corcovado 130–252 (Cárdenas et al., 2008) T. brevispira Martens, 1885 South Georgia Islands 0–16 (Martens, 1885), 2–15 (Strebel, 1908), 18–37 (Carcelles,

1953), 18–270 (Powell, 1951), n.d. (Lamy, 1911, Zelaya, 2005) T. ceciliae Houart, 2003 Antofagasta 1000–1300 (Houart, 2003) Off Caldera 434 (Houart and Sellanes, 2006) Off Coquimbo 600 (Houart and Sellanes, 2006) Off Concepción Bay (73.7°W) 900 (Houart and Sellanes, 2006) T. clenchi (Carcelles, 1953) Off Mar del Plata (55.6ºW) 90 (Pastorino, 2005) Off Gulf of San Matías (57.6ºW) 1062 (Pastorino, 2005) Off Gulf San Jorge (57.3ºW) n.d. (Pastorino, 2005)

Table 1: Species of Trophon (s.l.) arranged alphabetically showing their distribution and bathymetry. Coordinates of geographic toponyms are indicated in the

Appendix; USNM, Smithsonian National Museum of Natural History; n.d., no data were obtained.

64


26

Species - Distribution Bathymetry (m) and source East of Falkland/Malvinas Islands

(56.6ºW) 646–845 (Pastorino, 2005)

Staten Island n.d (Pastorino, 2005) Tierra del Fuego Island 342–353 (Pastorino, 2005) T. columbarioides Pastorino and Scarabino, 2008 Off Mar del Plata (54–55ºW) 209–382 (Pastorino and Scarabino, 2008) T. condei Houart, 2003 Ancud 1350 (Houart, 2003) Off Concepción Bay (73.7°W) 728–930 (Houart and Sellanes, 2006) T. coulmanensis coulmanensis Smith, 1907 South Sandwich Islands 93–121 (USNM) (2) Weddell Sea n.d. (USNM) (2) South Shetland Islands 220–1120 (Dell, 1990) (2) Bransfield Strait 809–1116 (USNM) (2) Western Antarctic Peninsula 294 (Aldea and Troncoso, 2008) Ross Sea 183 (Smith, 1907) (2), 351–1674 (Dell, 1990) (2) Cape Adare 329–366 (Smith, 1915) (2) George V Land 527 (Hedley, 1916) (2) Davis Sea n.d. (Thiele, 1912) (2) Kerguelen Islands 125–1218 (Cantera and Arnaud, 1985) (2) T. coulmanensis multilamellatus Numanami, 1996 East Antarctica (24ºE) 270–289 (Numanami, 1996) T. cribellum Strebel, 1908 South Georgia Islands 20–75 (Strebel, 1908), 22 (Zelaya, 2005), 44 (Carcelles, 1953) (3) T. cuspidarioides Powell, 1951 South Georgia Islands 120–204 (Powell, 1951) Peter I Island 410 (Aldea and Troncoso, 2008) T. declinans Watson 1882 Northwest of Heard Island (52.1ºS,

71.4ºE)274 (Watson, 1886)

Kerguelen Islands 30–190 (Cantera and Arnaud, 1985) Crozet Islands 115–235 (Cantera and Arnaud, 1985) Marion Island 99–113 (Powell, 1951), 126 (Watson, 1886), 0–527 (Branch et al.,

1991) East of Falkland/Malvinas Islands

(57ºW) 229–236 (Powell, 1951)

Drake Passage (59.8ºS, 68.8ºW) 1043–1208 (USNM) T. distantelamellatus Strebel, 1908 South Georgia Islands 64–74 (Strebel, 1908), 18–110 (Powell, 1951), 46–101, (USNM) T. drygalskii Thiele, 1912 South Sandwich Islands 161–210 (USNM) Weddell Sea 588 (Hain, 1990), 119–2315 (Gutt et al., 2000) South Shetland Islands and Bransfield

Strait210–426 (Dell, 1990)

Bransfield Strait n.d. (USNM)

65


27

Species - Distribution Bathymetry (m) and source Western Antarctic Peninsula 126 (USNM) Bellingshausen Sea 1426–1814 (Aldea and Troncoso, 2008) Ross Sea 311–348 (USNM), , 265–392 (Dell, 1990), , 292–457 (Smith, 1915) Davis Sea n.d. (Thiele, 1912) Enderby Land 193–300 (Powell, 1958) East Antarctica (24ºE) n.d. (Numanami, 1996) T. echinolamellatus Powell, 1951 South Sandwich Islands 93–228 (USNM) South Georgia Islands 220–320 (USNM) Weddell Sea 504 (Gutt et al., 2000) South Orkney Islands 284 (USNM) South Shetland Islands 115 (Aldea and Troncoso, 2008), 342 (Powell, 1951), 120–462

(USNM) Bransfield Strait 210–1373 (USNM) Western Antarctic Peninsula 37–800 (USNM) T. emilyae Pastorino, 2002 NW Amundsen Sea (54.8ºS, 129.8ºW) 549–1153 (Pastorino, 2002b) T. enderbyensis Powell, 1958 Enderby Land 193 (Powell, 1958) T. eversoni Houart, 1997 Kerguelen Islands 185 (Houart, 1997) T. fasciolarioides Pastorino and Scarabino, 2008 Off Bahía Blanca 1000 (Pastorino and Scarabino, 2008) Burdwood Bank 286–292 (Pastorino and Scarabino, 2008) T. geversianus (Pallas, 1774) Buenos Aires Province n.d. (Pastorino, 2005) South Atlantic Ocean (37.8ºS, 36.2ºW) 100 (Strebel, 1908) San Antonio Oeste 0 (Pastorino, 2005) Sierra Grande 0 (Pastorino, 2005) Puerto Lobos n.d. (Pastorino, 2005) Puerto Pirámides n.d. (Pastorino, 2005) Puerto Madryn n.d. (Pastorino, 2005) Gulf San Jorge n.d. (Pastorino, 2005) Puerto Deseado 5 (Pastorino, 2005) Punta Peñas 0–2 (Pastorino, 2005) Río Santa Cruz n.d. (Pastorino, 2005) Off Rio Santa Cruz (67.7ºW) 56–84 (Powell, 1951) Rio Gallegos n.d. (Pastorino, 2005) Falkland/Malvinas Islands 0–11 (Melvill and Standen, 1907) (4), 1–16 (Powell, 1951), 22

(Watson, 1886), 10–40 (Strebel, 1908), n.d. (Melvill and Standen, 1898), (Pastorino, 2005)

Burdwood Bank 102 (Melvill and Standen, 1912) (4), n.d. (Pastorino, 2005) Staten Island 0 (USNM), 0–641 (Pastorino, 2005) Usuahia n.d. (Strebel, 1908, Pastorino, 2005) Usuahia and Beagle Channel n.d. (Rochebrune and Mabille, 1889) Beagle Channel 0 (Pelseneer, 1903, Dell, 1971), 15–53 (Osorio, 1999)

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28

Species - Distribution Bathymetry (m) and source Cape Horn n.d. (Rochebrune and Mabille, 1889) Magellan Strait 0 Mutschke et al., 1998), 2–3 (USNM), 14–22 (Osorio, 1999), 27

(Powell, 1951), 0–296 (Pastorino, 2005), n.d. (Rochebrune and Mabille, 1889, Lamy, 1906, Houart, 1998, Linse, 2002)

Tierra del Fuego Island 0–1 (USNM), 0–31 (Pastorino, 2005), 27–38 (Powell, 1951) (4), n.d. (Smith, 1905, USNM)

Heard Island 137 (Watson, 1886) Western Antarctic Peninsula 30 (Lamy, 1906) (5) South Orkney Islands 16–18 (Melvill and Standen, 1907) (5) T. iarae Houart, 1998 Off Albardão 55 (Houart, 1998) Off Uruguay n.d. (Houart, 1998) T. leptocharteres Oliver and Picken, 1984 South Orkney Islands 15–30 (Oliver and Picken, 1984) South Shetland Islands 64–82 (USNM) Western Antarctic Peninsula 18–130 (USNM) T. longstaffi Smith, 1907 South Sandwich Islands 148–201 (USNM) South Georgia Islands 1299–1400 (USNM) Weddell Sea 123–446 (Gutt et al., 2000) Peter I Island 90–126 (Aldea and Troncoso, 2008) Ross Sea 47–75 (Smith, 1907), 8–124 (USNM), 37–146 (Hedley, 1911), 457

(Smith, 1915), 8–1080 (Dell, 1990) George V Land 22–732 (Hedley, 1916) Adelie Land 5–140 (Arnaud, 1972) Wilkes Land 128–146 (USNM) East Antarctica (40ºE) 5 (Numanami, 1996) T. macquariensis Powell, 1957 Macquarie Island 69 (Powell, 1957), 110–124 (USNM) T. mawsoni Powell, 1957 Macquarie Island 69 (Powell, 1957), 29–549 (USNM), n.d. (Hedley, 1916) (6) T. minutus Strebel, MS. Melvill and Standen, 1907 South Sandwich Islands 148–201 (Dell, 1990), 122–210 (USNM) South Georgia Islands 24–52 (Strebel, 1908) Drake Passage (56ºS, 61.5ºW) 47–54 (USNM) Magellan Strait 27–73 (USNM) South Orkney Islands 16–18 (Melvill and Standen, 1912), 20 (Oliver and Picken, 1984),

16–27 (Melvill and Standen, 1907) Weddell Sea 119–170 (Gutt et al., 2000) South Shetland Islands 38–82 (USNM) Bransfield Strait 210–240 (USNM), 210–265 (Dell, 1990) Western Antarctic Peninsula 6–37 (Dell, 1990), 53 (Aldea and Troncoso, 2008), 93–130 (Powell,

1951), 21–305 (USNM) Ross Sea n.d. (Dell, 1990) George V Land 46 (Hedley, 1916) (7) Adelie Land 31 (Arnaud, 1972) (7)

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29

Species - Distribution Bathymetry (m) and source Kerguelen Islands 24–158 (Cantera and Arnaud, 1985) (7) T. nucelliformis Oliver and Picken, 1984 South Orkney Islands 3–6 (Melvill and Standen, 1907) (8), 2–20 (Oliver and Picken, 1984) South Shetland Islands 44 (USNM) Western Antarctic Peninsula 4–6 (USNM) T. ohlini Strebel, 1904 South Atlantic Ocean (47.6ºS, 60.8ºW) 133–219 (Powell, 1951) West of Falkland/Malvinas Islands

(63ºW) 141–162 (Powell, 1951)

Burdwood Bank 124 (USNM) Magellan Strait 27 (Strebel, 1904), 38–92 (Linse, 2002) (9), 91–110 (USNM) Beagle Channel 13–135 (Linse, 2002) (9) Cape Horn 40 (Linse, 2002) (9) T. pallidus (Broderip, 1833) Falkland/Malvinas Islands 11 (Melvill and Standen, 1907) (10), 10–146 (Powell, 1951) Burdwood Bank 102 (Melvill and Standen, 1907) (10), 124–128 (USNM), 137–150

(Strebel, 1908) (12) Staten Island 118 (Powell, 1951) Off Tierra del Fuego Island (65–67.2ºW) 79–124 (USNM) Beagle Channel 15–53 (Osorio, 1999), 15–135 (Linse, 2002) Cape Horn 40–66 (Linse, 2002), 115 (USNM), 24–357 (Rochebrune and

Mabille, 1889) (10) (11) Drake Passage (56.3ºS, 67.2ºW) 121 (Powell, 1951) Magellan Strait 0 Mutschke et al., 1998), 14–35 (Osorio, 1999), 45–92 (Linse, 2002),

95 (Powell, 1951) Off Desolación Island (74.9–75ºW) 64–101 (USNM) Gulf of Corcovado 130 (Cárdenas et al., 2008) Gulf of Ancud 252 (Cárdenas et al., 2008) Crozet Islands 505 (Cantera and Arnaud, 1985) T. parodizi Pastorino, 2005 Le Maire Strait 229–265 (Pastorino, 2005) T. patagonicus (D'orbigny, 1839) Rocha n.d. (Houart, 1998) (13) Off Rocha 100 (Pastorino, 2005) Off Punta Rasa (54.6–54.7ºW) 26–54 (Pastorino, 2005) Mar Azul 55 (Pastorino, 2005) Mar del Plata n.d. (Pastorino, 2005) Miramar n.d. (Pastorino, 2005) Necochea 30–50 (Pastorino, 2005) T. pelseneeri Smith, 1915 Macaé 30–55 (Pastorino, 2005) Río de Janeiro 50–100 (Houart, 1991), 55–225 (Ríos, 1994) Off Rocha (34.8ºS, 54.4ºW) 25 (Pastorino, 2005) Buenos Aires n.d. (Pastorino, 2005) Necochea n.d. (Carcelles, 1944) Falkland/Malvinas Islands n.d. (Pastorino, 2005)

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30

Species - Distribution Bathymetry (m) and source West of Falkland/Malvinas Islands 229 (Smith, 1915) T. plicatus (Lightfoot, 1786) Río Grande do Sul n.d. (Ríos, 1994) Necochea 0 (Carcelles, 1944) (14) Off Bustamante Bay (65ºW) 82–88 (Pastorino, 2005) Comodoro Rivadavia n.d. (Pastorino, 2005) Cabo Blanco 82–88 (Powell, 1951) (14) Punta Peñas 2–3 (Pastorino, 2005) Falkland/Malvinas Islands 25 (Strebel, 1908), 79 (Powell, 1951) (14), 79 (Houart, 1998) (16),

n.d. (Melvill and Standen, 1898) (14) West of Shag Rocks (43.4ºW) 160 (Strebel, 1908) Burdwood Bank 137–150 (Strebel, 1908) Off Tierra del Fuego Island (65–67.2ºW) 82–128 (Pastorino, 2005) Tierra del Fuego Island n.d. (Pastorino, 2005) Staten Island 84–91 (Pastorino, 2005) Cape Horn 0 (Lamy, 1906) (14), 12–28 (Rochebrune and Mabille, 1889) (14),

n.d. (Pastorino, 2005) Usuahia 8–10 (Pastorino, 2005), 12–28 (Rochebrune and Mabille, 1889) (14) Beagle Channel 24–65 (Osorio, 1999), 55–82 (Pastorino, 2005) Magellan Strait 0 Mutschke et al., 1998), 24 (Osorio, 1999), 13–46 (Pastorino, 2005) Off Desolación Island (75ºW) 92–101 (Pastorino, 2005) Puerto Edén 0–18 (Dell, 1971) (15) Gulf Elefantes 0–15 Reid and Osorio, 2000) Off Gulf of Penas (83.9ºW) 298 (Pastorino, 2005) Estero Elefantes 0–15 Reid and Osorio, 2000) Pulluche Channel 62 (Osorio et al., 2006) Gulf of Ancud 252 (Cárdenas et al., 2008) T. poirieria Powell, 1951 South Shetland Islands 342 (Powell, 1951) Western Antarctic Peninsula 93–130 (Powell, 1951) South Georgia Islands n.d. (Carcelles, 1953) (17) T. scolopax Watson, 1882 Northwest of Heard Island (52.1ºS,

71.4ºE)274 (Watson, 1886)

Kerguelen Islands 60–620 (Cantera and Arnaud, 1985) Crozet Islands 330–600 (Cantera and Arnaud, 1985) T. scotianus Powell,1951 South Georgia Islands 0 (Carcelles, 1953), 97–101 (Dell, 1990), 107 (Powell, 1951), 18–

144 (Zelaya, 2005), 84–218 (USNM) Weddell Sea 437–519 (USNM), 202–617 (Hain, 1990) (18), 462–620 (Gutt et al.,

2000) Western Antarctic Peninsula 20–106 (USNM) Ross Sea 256–474 (Dell, 1990) East Antarctica (39.5ºE) 147 (Numanami, 1996) T. septus Watson, 1882 Kerguelen Islands 52 (Watson, 1886), 48–65 (Troncoso et al., 2001), 0–150 (Powell,

1957), 30–620 (Cantera and Arnaud, 1985)

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31

Species - Distribution Bathymetry (m) and source Crozet Islands 62–355 (Cantera and Arnaud, 1985) Marion and Prince Edward Islands 140–200 (Branch et al., 1991) T. shackletoni paucilamellatus Powell, 1951 South Georgia Islands 18 (Carcelles, 1953), 75 (Strebel, 1908) (19), 97–101 (Dell, 1990),

82–138 (Zelaya, 2005), 100–178 (Powell, 1951), 66–366 (USNM) South Sandwich Islands 121–228 (USNM), 278–329 (Powell, 1951) Southeast of South Orkney Islands

(61.4ºS, 41.9ºW) 593–598 (Dell, 1990)

South Orkney Islands 97–305 (USNM), 298–403 (Dell, 1990) South Shetland Islands 421–462 (USNM) Western Antarctic Peninsula 128–165 (Dell, 1990), 50–375 (USNM) Ross Sea 347–358 (USNM) T. shackletoni shackletoni Hedley, 1911 South Georgia Islands 102–137 (USNM) (21) Weddell Sea 123 (Gutt et al., 2000), n.d. (Hain, 1990) (20) South Orkney Islands 35 (Oliver and Picken, 1984) Ross Sea 13–37 (Hedley, 1911) (21), 293–549 (Smith, 1915) (21), 188–1890

(Dell, 1990) West of Macquarie Island (151ºE) 2746–3248 (Dell, 1990) George V Land 100–110 (Hedley, 1916) (21) Shackleton Ice Shelf 43 (Egorova, 1982) Davis Sea 110 (Hedley, 1916) (21) Amery Ice Shelf 456 (Powell, 1958) (21) Enderby Land 193–220 (Powell, 1958) (21) East Antarctica (24ºE) 275–310 (Numanami, 1996) T. triacanthus Castellanos, Rolán and Bartolotta, 1987 Off Gulf San Jorge (60°W) 600 (Castellanos et al., 1987) Falkland/Malvinas Islands 646–866 (USNM) T. vangoethemi Houart, 2003 Gulf of Corcovado 169 (Cárdenas et al., 2008) Off Concepción Bay (73.1–73.6°W) 350 (Houart, 2003), 530–613 (Houart and Sellanes, 2006) T. veronicae Pastorino, 1999 Northwest of South Georgia Islands

(50.5ºS, 43.5ºW) 298–1281 (Pastorino, 1999)

Desolación Island 675 (Pastorino, 1999) Off Southern Chile (46–46.1°S, 83.9–

84°W) 298–742 (Pastorino, 1999)

Boca del Guafo 200 (Osorio et al., 2006) "T." malvinarum Strebel, 1908 Falkland/Malvinas Islands 197 (Strebel, 1908) Beagle Channel 83 (Pastorino, 2005) (22)

(1) Cited as T. cinguliferus Pfeffer, 1886. Synonymized after Strebel (1908) and Cernohorsky (1977).(2) Cited as T. coulmanensis.(3) Misidentified as T. cinguliferus Pfeffer, 1886 according Zelaya (2005).

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APPENDIX

List of toponyms used in the Table 1 and their locations. AR, Argentina; AN, Antarctica; BR, Brazil; CL, Chile; UR, Uruguay.

Adelie Land, AN (136.2–142ºE)Albardão, BR (33.2ºS, 52.7ºW)Amery Ice Shelf, AN (70–75ºE)Amundsen Sea, AN (99–126ºW)Ancud, CL (41.9ºS, 73.8ºW)Antofagasta, CL (23.6ºS, 70.4ºW)Bahía Blanca, AR (39ºS, 62ºW)Beagle Channel (54.9–55.1ºS, 66.5–70.2ºW)Bellingshausen Sea, AN (70–99ºW)Boca del Guafo, CL (43.7ºS, 75ºW)Bransfield Strait, AN (63ºS, 59ºW)Buenos Aires (Province), AR (34.1–41ºS, 58.4–62.8ºW)Burdwood Bank (53.8–55.3ºS, 55.7–61.5ºW)Bustamante Bay, AR (45.1ºS, 66.5ºW)Cabo Blanco, AR (47.2ºS, 65.7ºW)

Caldera, CL (27.1ºS, 70.8ºW)Cape Adare, AN (69.7ºS, 163.4ºE)Cape Horn (56ºS, 67.2ºW)Comodoro Rivadavia, AR (45.9ºS, 67.5ºW)Concepción Bay, CL (36.6–36.7ºS, 73–73.1ºW)Coquimbo, CL (30ºS, 71.4ºW)Crozet Islands (46–46.5ºS, 50.2–52.3ºE)Davis Sea, AN (80–105ºE)Desolación Island, CL (52.8–53.4ºS, 73.1–74.7ºW)Drake Passage (56–62ºS, 58–69ºW)Enderby Land, AN (44.6–59.6ºE)Estero Elefantes, CL (45.8º–46.3ºS, 73.7ºW)Falkland/Malvinas Islands (51–52.5ºS, 57.7–61.3ºW)George V Land, AN (142–153.8ºE)Gulf Elefantes, CL (46.3–46.6ºS, 73.8ºW)Gulf of Ancud, CL (41.8–42.3ºS, 72.6–73.4ºW)Gulf of Corcovado, CL (42.3–43.5ºS, 72.8–73.5ºW)Gulf of Penas, CL (46.8–47.7ºS, 74.1–75.7ºW)Gulf of San Matías, AR (40.8–42.3ºS, 63.5–65.2ºW)Gulf San Jorge, AR (44.9–47.1ºS, 65.5–67.6ºW)Heard Island (53–53.2ºS, 73.3–73.8ºE)Kerguelen Islands (48.5–49.8ºS, 68.7–70.6ºE)

32

(4) Cited as T. philippianus Dunker, 1878. Synonymized after Pastorino (2005). (5) According Pastorino (2005) are probably T. nucelliformis Oliver and Picken, 1984 or T.maquariensis Powell, 1957, or T. echinolamellatus sensu Powell (1951). (6) Cited as T. albolabratus, according Powell (1957). (7) Cited as T. condensatus Hedley, 1916. Synonymized after Dell (1990). (8) Misidentified as T. cinguliferus Pfeffer, 1886 according Oliver and Picken (1984). (9) Conferred specimens. (10) Cited as T. crispus (Couthouy M.S. Gould, 1849). (11) Cited as T. fasciculatus (Hombron and Jacquinot, 1848). Synonymized after Powell (1951).(12) Cited as T. crispus var. burwoodianus (Couthouy M.S. Gould, 1849). Synonymized after Powell (1951). (13) Misidentified as T. plicatus according Pastorino (2005). (14) Cited as T. laciniatus (Martyn, 1784) (Pastorino, 2005). (15) Cited as T. lamellosa (Gmelin, 1791) (Pastorino, 2005). (16) Misidentified as T. iarae according Pastorino (2005). (17) Zelaya (2005) doubts this record since no reference in collections was neither found nor well documented. (18) Cited as “T. sp.1” according Numanami (1996). (19) Cited as T. laciniatus, but according Powell (1951) are probably T. shackletoni paucilamellatus.(20) Cited as T. shackletoni, conferred. (21) Cited as T. shackletoni.(22) Established under dubious genus.

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Le Maire Strait, AR (54.8ºS, 64.9ºW)Macaé, BR (22.4ºS, 41.8ºW)Macquarie Island (54.5–54.8ºS–158.8–159ºE)Magellan Strait¸ CL (53.5ºS–70.8ºW)Manuel Rodriguez Island, CL (52.7ºS–73.8ºW)Mar Azul, AR (37.3ºS, 57ºW)Mar del Plata, AR (38ºS, 57.5ºW)Marion Island (46.8–47ºS, 37.6–37.9ºE)Miramar, AR (38.3ºS, 57.8ºW)Necochea, AR (38.6ºS, 58.7ºW)Ninualac Channel, CL (45ºS, 73.8–74.4ºW)Peter I Island, AN (68.8–68.9ºS, 90.4–90.7ºW)Pichilemu, CL (34.4ºS, 72ºW)Prince Edward Island (46.6–46.7ºS, 37.9–38 ºE)Puerto Deseado, AR (47.8ºS, 65.9ºW)Puerto Edén, CL (49.2ºS, 74.4ºW)Puerto Lobos, AR (42ºS–65.1ºW)Puerto Madryn, AR (42.8ºS–65ºW)Puerto Pirámides, AR (42.6ºS–64.3ºW)Pulluche Channel, CL (45.8ºS, 74.6ºW)Punta Médanos, AR (36.9ºS, 56.7ºW)Punta Peñas, AR (49.2ºS, 67.6ºW)Punta Rasa, AR (36.3ºS, 56.8ºW)Río de Janeiro, BR (22.9ºS, 43.2ºW)Rio Gallegos, AR (51.6ºS, 69.2ºW)Río Grande do Sul, BR (29.3–33.8ºS, 49.7–53.3ºW)Río Santa Cruz, AR (50.1ºS, 68.3ºW)Rocha, UR (34.6ºS, 54ºW)Ross Sea, AN (171ºE–150ºW)San Antonio Oeste, AR (40.8ºS, 64.9ºW)Shackleton Ice Shelf, AN (95–105ºE)Shag Rocks (53.6–53.7ºS, 41.8–42ºW)Sierra Grande, AR (41.6ºS, 65ºW)South Georgia Islands (54–54.9ºS, 35.8–38ºW)South Orkney Islands (60.5–60.8ºS, 44.4–46ºW)South Sandwich Islands (56.3–59.5ºS, 26.1–27.7ºW)South Shetland Islands, AN (61–63.4ºS, 53.9–62.8ºW)Staten Island, AR (54.7–54.9ºS, 63.8–64.8ºW)Tierra del Fuego Island (52.4–55ºS, 65.1–70.5ºW)Usuahia, AR (54.8ºS, 68.3ºW)Weddell Sea, AN (10–60ºW)Wellington Island, CL (48.7–50.1ºS, 74.3–75.3ºW)Western Antarctic Peninsula, AN (63–70ºS)Wilkes Land, AN (100.5–136.2ºE)

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Pastorino G (1999). A new species of gastropod of the genus Trophon Montfort, 1810 (Mollusca: Gastropoda: Muricidae) from subantarctic waters. The Veliger, 42: 169–174.

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Pastorino G (2002b). Two new Trophoninae (Gastropoda: Muricidae) from Antarctic waters. Malacologia, 44(2): 353–361.

Pastorino G (2005). A revision of the genus Trophon Monfort, 1810 (Gastropoda: Muricidae) from southern South America. The Nautilus, 119(2): 55–82.

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ADDENDA

During the edition of this volume of Thalassas, was publish the following paper: Harasewych MG, Pastorino G (2010). Trophonella (Gastropoda: Muricidae), a new genus from Antarctic waters with description of a new species. The Veliger 51(1): 85-103.

The authors describe a new species under the genus Trophonella from Laurie Island (South Orkney Islands ) called Trophonella rugosolamellata. Besides four species (Trophon scotianus, T. echinolamellatus, T. enderbyensis and T. eversoni) previously cited by us in this paper like Trophon was translated to the new genus Trophonella.

DIFFERENTIAL GENE FLOW BETWEEN POPULATIONS OF MYTILUS GALLOPROVINCIALIS DISTRIBUTED ALONG

IBERIAN AND NORTH AFRICAN COASTS

ABSTRACT

This population genetics study on Mytilus galloprovincialis aims to clarify whether northern Moroccan populations fit into the biogeographical pattern of Iberian populations characterized by a main genetic discontinuity at the Almería - Orán Oceanographic Front (AOOF). We report a reduced gene flow between northern Moroccan mussels distributed at both sides of Gibraltar Strait and a limited gene flow between Iberian and Moroccan populations in the Alboran Sea. These results observed with microsatellites do not fully match previous ones where Moroccan populations from Alboran did not differ from other Atlantic populations.

INTRODUCTION

Previous studies using molecular markers such as allozymes (Sanjuan et al., 1994), mtDNA (Quesada et al., 1995), and microsatelites (Diz & Presa, 2008) have shown the existence of two differentiated population sets of Mytilus galloprovincialis in Iberia, one extending in continuity from the Cantabric Sea (NE Iberia) to the Alboran Sea (SE Iberia), and another one in the Mediterranean. The oceanographic properties of the Almería - Oran Oceanographic Front (AOOF; Tintoré et al., 1998) have been proposed as the causative force of such divide i.e. acting as an effective barrier to gene f low between those population sets. The present work aimed to clarifying genetic status of Northern Moroccan populations of M. galloprovincialis in the Alboran Sea using microsatellite markers, i.e., to test if they fit into the Iberian biogeographical pattern characterized by two gene pools distributed at both sides of the AOOF exclusion zone, respectively.

(1) ECIMAT - Faculty of Marine Sciences, University of Vigo, 36310 Vigo, Spain, [email protected](2) Unité Biosurveillance, Laboratoire Alimentation,Environnement et Santé, Faculté des Sciences et Techniques, Université Cadi Ayyad, Marrakech, Morocco.(3) Université Abdelmalek Essaâdi, Faculté des Sciences, Laboratoire de Biologie Appliquée et Pathologie, BP. 2121, Mhannech 2, 93002 Tétouan, Morocco

Thalassas, 25 (3) Special issue: 75-78An International Journal of Marine Sciences

Key words: Mytilus galloprovincialis, genetic structure, gene flow, Alboran Sea, microsatellites

Y. OUAGAJJOU(1,2), A. AGHZAR(1,3), M. MIÑAMBRES(1), P. PRESA(1) & M. PÉREZ(1)

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Y. OUAGAJJOU, A. AGHZAR, M. MIÑAMBRES, P. PRESA & M. PÉREZ

MATERIAL AND METHODS

Seven populations of M. galloprovincialis were sampled (35-50 individuals each) at intertidal areas of the northern Atlantic (three from Atlantic Morocco, N = 135, and one from Atlantic Iberia, N = 40), the western Mediterranean (two from Alboran Morocco, N = 87, and one from Mediterranean Iberia, N = 38) (Figure 1). DNA from 300 mussels was extracted following the CTAB protocol (Sokolov, 2000) and genotyped with seven polymorphic microsatellites, four of them previously described (Mgµ1, Mgµ3, Mgµ4, and Mgµ5; Presa et al., 2002) and three ones unpublished (MgµD5- (CA)6, MgµD10-(CA)6 and MgµH7 (CAAA)9). Amplification conditions for published markers conformed to those described in Presa et al. (2002) and the three new markers were amplified at 55ºC x 1.6 mM MgCl2 (MgµD5), 58ºC x 1.3 mM MgCl2 (MgµD10), and 57ºC x 1.5 mM MgCl2 (MgµH7), following a thermocycler routine of 95ºC x 5 min, 35 cycles x (94ºC x 1 min, annealing temperature x 1 min and 72ºC x 1 min), plus a final extension step

at 72ºC x 15 min. Amplicons were electrophoresed in an ALFexpressII automatic fragment analyser (GE Healthcare) and alleles were sized using molecular ladders. Genetic parameters (allelic frequencies, HO, HE and FIS) were calculated with Genepop 4 (Raymond & Rousset, 1995) and allelic series were tested for null alleles with Micro-Checker (van Oosterhout et al., 2004). Fixation index between populations (FST) and differences in population diversity between Atlantic and Mediterranean populations were calculated with Fstat 3.9.5 (Goudet, 1995). Analysis of molecular variance (AMOVA) (Excoffier et al., 1992) as implemented in Arlequin 2.0 (Schneider et al., 1997) was used to calculate the distribution of the genetic variance between subpopulations of the Atlantic and the Alboran Sea.

RESULTS

A significant heterogeneity of allele frequencies was observed at six out of seven loci between samples of the four areas studied. A significant variation was observed between the two Moroccan groups, Atlantic and Alboran, (AMOVA, d.f. = 1; 3.04% variation), and this variation was larger than that within groups (AMOVA, d.f. = 3; 1.01% variation). The main multilocus discontinuity among Moroccan samples was observed in Gibraltar Straight, i.e. the two samples from Alboran Morocco (MEnad: Nador;

Figure 1: Map location of the seven M. galloprovincialis populations analysed,

as three from Atlantic Morocco (ATtan1, ATtan2, ATlar), two from Alboran Morocco (MEtet, MEnad), and one reference population from

both, the Atlantic (ATrib) and the Mediterranean (MEoro).

Table 1: Estimating Fst of Weir and Cockerham (1996) for each pair of the

Moroccan and the two outgroup populations of M. galloprovincialis over loci. Initial nominal level (* p < 0.05) was corrected with

Bonferroni test for multiple comparisons.

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DIFFERENTIAL GENE FLOW BETWEEN POPULATIONS OF Mylitus galloprovincialis DISTRIBUTED ALONG IBERIAN AND NORTH AFRICAN COASTS

MEtet: Tétouan) were significantly divergent from those in Atlantic Morocco (ATtan: Tanger; ATlar: Lârache) (Table 1). The phylogenetic groups comprised populations from western Mediterranean (MEoro: Oropesa-Almería), Atlantic Iberia (ATrib: Ribeira-Galicia), Atlantic Morocco (ATlar: Lârache; ATtan1: north Tanger ; ATtan2: south Tanger) and Alboran Morocco (MEnad: Nador; MEtet: Tétouan) (Figure 2).

DISCUSSION

The genetic divergence between northern Moroccan mussels and other European populations of M. galloprovincialis has been reported in previous studies, i.e. Comesaña et al. (1998) for an Atlantic divergence, or Jaziri & Benazzou (2002) for a Mediterranean divergence. In addition, a population split between northern Moroccan populations has been made patent herein with microsatellites. Although Iberian populations have shown a main interbasin restriction to gene flow imposed by the AOOF barrier (e.g., Diz & Presa, 2008), the main biogeographical breakpoint determining a reduced gene flow between northern Moroccan populations seems to be Gibraltar Strait after present data. This result contrasts with previous allozymic studies on northern Moroccan mussels in which Nador and Tétouan populations from Alboran Sea showed null (Comesaña et al., 1998) or very weak divergence from Atlantic populations (Daguin & Borsa, 1999; Jaziri & Benazzou, 2002). Another interesting result is

the genetic divergence between Alboran populations from Morocco versus those from Atlantic Iberia (e.g., ATrib), these later showing a genetic continuity from the Cantabric Sea to the Almería-Oran Oceanographic Front (Diz & Presa, 2008). This result suggests that such distinct distributions are likely determined by the specific current dynamics of the Alboran Sea, characterised by gradients of temperature and salinity, strong water currents, and multiple eddies and gyres that flow anticyclonically from SE Iberian Peninsula (Almeria) to Algeria (Oran) (Tintoré et al., 1998). The oceanographical confinement of Alboran mussels from northern Morocco, leaning south from the main Atlantic current that flows eastward through Gibraltar Strait, could help to explain the gene flow limitation among Alboran Sea mussel populations.

ACKNOWLEDGEMENTS

This research has been funded by AECID (Ministerio Español de Asuntos Exteriores y Cooperación) through grants PCI-A/5248/06, PCI-A/011426/07, and a research scholarship II-A from MAEC-AECID #0000215094 (2007-2008) to A. Aghzar.

REFERENCES

Comesaña, A.S., Posada, D. and Sanjuan, A. (1998) Mytilus galloprovincialis Lmk. in Northern Africa. J. Exp. Mar. Biol. Ecol., 223(2): 271-283.

Daguin, C. and Borsa, P. (1999) Genetic characterisation of Mytilus galloprovincialis Lmk. in North West Africa using nuclear DNA markers. J. Exp. Mar. Biol. Ecol., 235: 55-65.

Diz, A.E. and Presa, P. (2008) Regional patterns of microsatellite variation in Mytilus galloprovincialis from the Iberian Peninsula. Mar. Biol., 154(2): 277-286.

Excoffier, L., Smouse, P.E. and Quattro, J.M. (1992) Analysis of molecular variance inferred from metric distances among DNA haplotypes: Application to human mitochondrial DNA restriction data. Genetics, 131: 479–491.

Figure 2: Neighbor-joining tree built with allelic frequencies from seven

microsatellite systems. Branch support figures are percentages from 1,000 bootstrap tree replicates.

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Y. OUAGAJJOU, A. AGHZAR, M. MIÑAMBRES, P. PRESA & M. PÉREZ

Goudet, J. (1995) Fstat (vers. 2.9.3): a computer program to calculate F-statistics. J. Hered., 86: 485-486.

Jaziri, H. and Benazzou, T. (2002) Différenciation allozymique multilocus des populations de moule Mytilus galloprovincialis LmK. des côtes marocaines. C. R. Biologies, 325: 1175-1183.

Presa, P., Perez, M. and Diz, A. (2002) Polymorphic microsatellite markers for blue mussels (Mytilus spp.). Conservation Genetics, 3: 441-443.

Quesada, H., Beynon, C.M. and Skibinski, D.O.F. (1995) A mitochondrial DNA discontinuity in the mussel Mytilus galloprovincialis Lmk: pleistocene vicariance biogeography and secondary intergradation. Mol. Biol. Evol. 12: 521-524.

Raymond, M. and Rousset, F. (1995). GENEPOP (version 1.2): Population genetics software for exact tests and ecumenicism. J Hered. 86: 248–249.

Sanjuan, A., Zapata, C. and Alvarez, G. (1994) Mytilus galloprovincialis and M. edulis on the coasts of the Iberian Peninsula. Mar. Ecol. Prog. Ser., 113: 131-146.

Schneider, S., Kueffer, J.M., Roessli, D. and Excoffier, L. (1997) Arlequin vs. 1.1. A software for population genetic data analysis. Genetics and Biometry Laboratory, University of Geneva, Switzerland. Available at http://anthropologie.unige.ch/arlequin.

Sokolov, E.P. (2000) An improved method for DNA isolation from mucopolysaccharide-rich Molluscan tissues. J. Mollus. Stud., 66: 573-575.

Titoré, J., La Violette, P.E., Blade, I. and Cruzado, G. (1998) A study of an intense density front in the eastern Alboran Sea: the Almeria-Oran front. J. Phys. Oceanogr., 18: 1384-1397.

van Oosterhout, C., Hutchinson, W.F., Wills. D.P.M. and Shipley, P. (2004) Micro-Checker: Software for identifying and correcting genotyping errors in microsatellite data. Mol. Ecol. Notes, 4: 535-538.

Weir, B.S., and Cockerham, C.C. (1984). Estimating F-Statistics for the analysis of population structure. Evolution, 38: 1358–1370.


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DISTRIBUTION AND POPULATION STRUCTURE OF PATELLA VULGATA LINNAEUS, 1758 (GASTROPODA: PATELLIDAE) ON INTERTIDAL SEAWALLS AND ROCKY SHORES IN THE RÍA DE

FERROL (GALICIA, NW IBERIAN PENINSULA)

ABSTRACT

Intertidal seawalls are a common feature on the shoreline of many urbanized coastal areas. In the Ría de Ferrol (Galicia, NW Iberian Peninsula), many seawalls are built vertically and have replaced or fragmented most of the natural horizontal rocky shores. Grazing gastropods, including the limpet, Patella vulgata Linnaeus, 1758, play an important role in the structuring of the assemblages of intertidal organisms,

by affecting the distribution and abundance of algae, sessile and mobile invertebrates. In order to compare patterns of abundance and population structure of P. vulgata on intertidal horizontal rocky shores and vertical seawalls in the Ría de Ferrol, four sampling stations were selected at the middle part of the ria, corresponding to semi-exposed areas. At each station, two rocky shores and two seawalls extensive enough for the intended sampling were selected and two sites separated by 5-10 m were visually sampled at each seawall/rocky shore. There were no clear differences regarding abundance, frequency of occurrence and population structure between the two studied habitats. Differences were found between sites (at the scale of metres) within any given seawall or rocky shore. Nevertheless, at some stations maximal sizes of limpets were greater on rocky shores than on seawalls. These results need to be further explored by manipulative experiments in order to understand whether seawalls constitute a surrogate habitat for limpets.

(1) Estación de Bioloxía Mariña da Graña, Universidade de Santiago de Compostela, Casa do Hórreo,Rúa da Ribeira 1, E-15590, A Graña, Ferrol, Spain.e-mail: [email protected](2)Departamento de Zooloxía e Antropoloxía Física, Universi-dade de Santiago de Compostela,Campus Sur, E-15782, Santiago de Compostela, Spain.(3)Instituto de Acuicultura, Universidade de Santiago de Compostela,Campus Sur, E-15782, Santiago de Compostela, Spain.

Key words: Patella vulgata; Gastropoda; artificial; seawall; rocky shore; intertidal; population; distribution; Ría de Ferrol; Iberian

Peninsula; Atlantic Ocean

GUILLERMO DÍAZ-AGRAS(1), JUAN MOREIRA(1), RAMIRO TATO(1), XANDRO GARCÍA-REGUEIRA(1)

& VICTORIANO URGORRI(1,2,3)

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GUILLERMO DÍAZ-AGRAS, JUAN MOREIRA, RAMIRO TATO, XANDRO GARCÍA-REGUEIRA & VICTORIANO URGORRI

INTRODUCTION

The continuous town-planning development associated to the constant growing of human population makes the urbanized areas have a greater and greater impact on the natural ecosystems (Carroll et al., 2004). It has been estimated that approximately between 30 and 40% of the human population live at present in coastal areas or next to them (Small & Nicholls, 2002) and it is foreseen that this percentage will grow up to 60% towards the year 2030 (Pickett et al., 2001). This means a proliferation of artificial structures as jetties, breakwaters, groynes, pilings, pontoons and seawalls, which destroy and fragment the natural habitats and add new structures to the marine ecosystems (McDonnell & Pickett, 1990; Glasby & Connell, 1999). These new structures differ from the natural ones in composition, orientation and texture of the surface as well as in the diversity and characteristics of the microhabitats they host (Chapman & Bulleri, 2003). Although previous work suggests that these new structures provide with new habitats and might be surrogates for natural rocky shores (Thompson et al., 2002), recent studies have shown that the greater differences between intertidal seawalls and natural rocky areas are not only in the composition of biological assemblages but also in the relative abundance of common species (Chapman,

2003; Chapman & Bulleri, 2003; Bulleri & Chapman, 2004). Understanding how these new structures affect the processes and the assemblages they host, is the key to try to mitigate the effects they have on the natural habitats to enable the design of artificial structures that have a lower impact on the coastal ecosystems and allow to host a diversity of organisms similar to the present on natural rocky shores.

To date, numerous studies have been carried out on the contamination level of water and sediment or on the effects of different pollutants on marine organisms (Thomas, 1999; Biselli et al., 2000; Diez et al., 2002). However, very few studies have been carried out on the impact that the artificial structures that replace the natural rocky areas have on the assemblages of intertidal organisms. In general, these studies have been done in very specific areas around the world as Australia (Chapman, 2003) and Italy (Bulleri & Chapman, 2004), where the tidal ranges vary between 1 and 2 metres. The intertidal zone of the Galician rias (NW Iberian Peninsula) has a tidal range of up to 4 m and a large diversity of natural habitats inhabited by a rich and diverse benthic fauna (e.g. Junoy & Viéitez, 1990; Troncoso & Urgorri, 1991). The shoreline of the rias is nowadays highly urbanized because of the concentration of population in coastal areas; many natural areas have been replaced or fragmented by

Figure 1: Location of the Ría de Ferrol and of sampling stations. AP, A Palma; SF, San Felipe; OB, O Baño; OV, O Vispón.

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DISTRIBUTION AND POPULATION STRUCTURE OF Patella vulgata LINNAEUS, 1758 (GASTROPODA: PATELLIDAE) ON INTERTIDAL SEAWALLS AND ROCKY SHORES IN THE RÍA DE FERROL (GALICIA, NW IBERIAN PENINSULA)

the construction of vertical seawalls, marinas and a number of harbour facilities. To date, no study has been done on the impact of the artificial structures on the intertidal assemblages of the rias.

In the Galician rias, intertidal seawalls are usually built vertically and made of granite, which is the material making up most of the natural shores. In many areas, seawalls are extensive and constitute the most common artificial habitat. Preliminary observations show that intertidal seawalls are colonized by a series of algae and invertebrates, including several species of limpets and snails. The Mollusca, sessile and vagile, are an important and varied component of the natural populations of invertebrates on the Galician coasts. For example, the bivalve, Mytilus galloprovincialis Lamarck, 1819, is very frequent on natural rocky shores and intertidal seawalls where it constitutes extensive belts at mid-tidal levels; on natural shores, mussel beds also provide with habitat to a large suite of organisms. Among the intertidal molluscs, grazing gastropods also play an important role in the intertidal assemblages (Underwood et al., 1983), for example, controlling the growth and distribution of algae (Underwood, 1980; 1998; Underwood & Jerkanoff, 1981) and ‘bulldozing’ small sessile specimens (Denley & Underwood, 1979). Among these grazers, the limpet, Patella vulgata Linnaeus, 1758, is one of the most common and numerous on natural habitats of the Galician coasts and is also present on intertidal vertical seawalls. This limpet mostly grazes on diatoms, settling stages of algae and filamentous and blue green algae growing on the rock surface and shows homing behaviour (Evans & Williams, 1991). Previous studies done on other limpets in other parts of the world (Chapman, 2006) show that the populations of some species inhabiting intertidal natural rocky shores and seawalls are similar as regards presence and frequency of appearance. However, there are differences in behaviour and performance between natural and artificial habitats, for example, as regards nourishing and mobility habits (Bulleri et al., 2004), sizes and reproductive output (Moreira et al., 2006).

Previous observations indicate that P. vulgata is a common species on intertidal seawalls. However, it is not known whether there are differences in abundance and population structure among natural rocky shores and seawalls. If they were found, this would mean that seawalls do not make up a suitable habitat for the populations of P. vulgata and therefore, they could not be considered as surrogate for natural habitats.

In this paper, we present a comparison of abundance, frequency of occurrence and population size-structure of the limpet, P. vulgata, among intertidal seawalls made of granite blocks and natural granitic rocky shores, located at a highly urbanized ria, i.e., the Ría de Ferrol.


Study sites and sampling

Sampling was done in four stations in the middle area of the Ría de Ferrol (Galicia, NW Iberian Peninsula; Figure 1) because the shoreline has vertical seawalls and horizontal rocky shores which are extensive enough to do the intended sampling. Inner areas of the ria were not sampled because the adequate rocky shores were not available; similarly, the outer ria has no seawalls extensive enough for the same purpose. Sampling was done in summer 2008 (August) and winter 2009 (February); at each station, two seawalls and two rocky shores (locations) were sampled. On each location (seawall or rocky shore) three heights representing different assemblages of organisms were chosen to examine the abundance, frequency of occurrence and sizes of Patella vulgata: 3-3.5 m (highshore), 2-2.5 m (midshore) and 1.5-2 m (lowshore); heights varied slightly depending on the place. Tidal level below 1.5 m was not sampled because it was not available in each location. The sampling design did not eliminate potential sources of confounding due to intrinsic characteristics of locations, but was a sensible scheme on the fragmented shoreline of the Ría de Ferrol. All stations were, however, located in the semi-exposed

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Figure 2: Densities of Patella vulgata (mean number per quadrat + SE) for midshore at each site on seawalls and rocky shores at each station. AP, A Palma;

SF, San Felipe; OB, O Baño; OV, O Vispón. Legend for sites: W1-1, seawall 1 - site 1; R1-1, rocky shore 1 - site 1

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Figure 3: Densities of Patella vulgata (mean number per quadrat + SE) for lowshore at each site on seawalls and rocky shores at each station. AP, A Palma;

SF, San Felipe; OB, O Baño; OV, O Vispón. Legend for sites: W1-1, seawall 1 - site 1; R1-1, rocky shore 1 - site 1.

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Figure 4: Length-frequency distribution of Patella vulgata on seawalls and rocky shores at each station in summer and winter. Black bars, rocky shores; white

bars, seawalls; n, total number of individuals measured; AP, A Palma; SF, San Felipe; OB, O Baño; OV, O Vispón. Results of KS tests are shown.

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zone of the Ría de Ferrol and apparently experienced similar wave-wash due to the intense maritime traffic. In addition, because seawalls were built vertically and are not gently sloped, comparisons among seawalls of different slope were not possible. Furthermore, patches of vertical rocky shores are not present in the Ría de Ferrol and therefore could not be sampled for comparisons.

Two replicate sites, approximately 5 m long and separated by 5-10 m were selected at each tidal level at each seawall and rocky shore. Five replicate quadrats (20 x 20 cm each) were randomly positioned in each site. Quadrats within the same site were separated by at least 50 cm. On seawalls and rocky shores, quadrats were placed at least 10 cm away from crevices. Numbers and sizes (shell length) of P. vulgata were counted and measured respectively in each quadrat.

Analysis of data

Abundances of P. vulgata were compared between habitats (seawall vs rocky shore) for each tidal level at each station by means of analysis of variance (three-factor ANOVA), to test for effects of habitat (fixed), location (nested in habitat) and site (nested in habitat and location). Analyses were done separately for summer and winter. Homogeneity of variances was checked using Cochran s test before analysis and data were transformed when appropriate. Data were analyzed untransformed when homogeneity of variances could not be achieved. ANOVA is a robust analysis despite heterogeneous variances when there are many independent replicates and sizes of samples are equal (Underwood, 1997).

To compare the frequency of occurrence of P. vulgata between habitats at each station regardless of actual densities, counts of presence/absence were added for each tidal level and habitat (Chapman, 2006); frequencies were compared through χ2 contingency tests separately for summer and winter.

For each station, the length-frequency distribution of limpets on seawalls and rocky shores were compared by means of Kolmogorov-Smirnov tests (KS). To achieve that, frequency distributions were constructed by considering all limpets present at the three tidal levels at the two seawalls and the two rocky shores.

RESULTS

Comparisons of abundance of Patella vulgata among seawalls and rocky shores did not show a clear pattern for midshore and lowshore (Tables 1, 2). Analyses were not done for highshore because of the low numbers of limpets there. When there were differences between habitats, those were not consistent between summer and winter. For example, at midshore level at A Palma and O Baño, there were more limpets on the seawalls than on the rocky shores in summer and there were no significant differences in winter (Figures 2-3). In general, there were no differences between seawalls or rocky shores at the same location apart from both rocky shores at lowshore at San Felipe in winter. On the contrary, significant differences were common between sites within the same seawall or rocky shore for both midshore and lowshore.

Frequencies of occurrence of P. vulgata were compared between habitats for each station through χ2 contingency tests, adding all the counts of presence/absence across either seawalls or rocky shores for each tidal level and sampling period. When there were significant differences (San Felipe and A Palma), limpets tended to be more frequent on seawalls than on rocky shores for midshore and the opposite pattern was found for lowshore, i.e. limpets were more frequent on rocky shores (Table 3). At O Baño and O Vispón there were no significant differences between habitats.

Kolmogorov-Smirnov tests showed that there were significant differences in sizes of limpets in summer and winter at A Palma and O Baño and in winter at O

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Vispón (Figure 4). In general, limpets longer than 30 mm tended to be more frequent on rocky shores than on seawalls although this was not true for San Felipe and in summer at O Vispón.

DISCUSSION

There were no consistent differences across stations on abundance and frequency of occurrence among populations of Patella vulgata on seawalls and rocky shores at the Ría de Ferrol. Similar patterns of abundance were observed for other limpets, namely Patelloida alticostata, P. latistrigata and Siphonaria denticulata, on seawalls and rocky shores at Sydney

Harbour (Chapman, 2006; Moreira et al., 2006). On the contrary, other limpets such as Cellana tramoserica, Patella aspera and P. rustica showed greater densities on rocky shores than on seawalls (Bulleri & Chapman, 2004; Bulleri et al., 2004). Furthermore, Guerra-García et al. (2004) found greater numbers of Patella ferruginea in artificial breakwaters than on natural shores. In general, when differences are observed those have been suggested to be related to the very nature of the habitat, i.e. seawalls provide a different habitat because they are vertical and lack microhabitats such as crevices and tidal pools (Chapman, 2006). Indeed, the physical characteristics of the habitat may have

Table 1

Table 2

87


a great influence in processes such as recruitment, competition and predation, which, in turn, affect the structure of populations (McGuinness, 1989; Underwood & Chapman, 1992).

There was a lack of a consistent pattern in differences in abundance between habitats. In general, differences were found between sites within locations for most of the studied stations. According to the intraspecific variability among populations of P. vulgata, these differences might be related to the aggregation of specimens in relation to trophic resources or use of habitat, being indifferent whether they are on rocky shores or seawalls. On natural

rocky shores, P. vulgata shows great behavioural plasticity (Hartnoll & Wright, 1977); for example, there are differences in patterns of foraging activity according to inclination of substratum, geographical latitude, topography and cover of sessile organisms (Little et al., 1988; Williams et al., 1999). On the contrary, Santini et al. (2004) pointed out that foraging behaviour varies depending on the time of the year rather than substratum being vertical or horizontal; this suggests that populations are very variable. Nevertheless, Bulleri et al. (2004) showed that differences in topography among seawalls and rocky shores may translate in differences in patterns of long-term dispersal; thus, many seawalls are made

Table 1: Analyses of densities of Patella vulgata at

midshore on seawalls and rocky shores at the Ría de Ferrol. ns, not significant (p>0.05); *,

p<0.05; **, p<0.01; ***, p<0.001.

Table 2: Analyses of densities of Patella vulgata at

lowshore on seawalls and rocky shores at the Ría de Ferrol. ns, not significant (p>0.05); *,

p<0.05; **, p<0.01;***, p<0.001.

88


of stone blocks separated by crevices which can be a physical limit for the movement of limpets. In our case, the studied seawalls at the Ría de Ferrol have, in many cases, crevices among blocks but it is not known yet whether this can affect biological performance of P. vulgata there, e.g. foraging activity and intra- and interespecific competition.

At some stations, limpets tended to be more frequent at midshore on seawalls than on rocky shores while the opposite pattern was found for lowshore. This fact could be related to differences between habitats in the vertical extent of intertidal space and the cover ofsessile organisms. At both habitats, cover of barnacles at midshore was similar while at lowshore mussel beds appeared to be denser on seawalls. In addition, on seawalls the intertidal extent is about 3.0-3.5 m while on the studied rocky shores that is about >10 m; therefore, distances among tidal levels and among different sessile assemblages (i.e. barnacles and mussel beds) are smaller on seawalls. Presence of mussel beds favour recruitment of limpets (Lewis & Bowman, 1975) and thus it is likely that limpets would migrate from those beds to higher on the shore as they grow in size (Hobday, 1995), where space is not occupied by mussels. In addition, because on seawalls mussel beds are relatively close to limpets at midshore (at the scale of tens of centimetres rather than of metres) limpets could set their home

scars close to those and benefit of protection against desiccation (Lewis & Bowman, 1975). Nevertheless, patterns of homing behaviour on seawalls are not yet known and this needs to be further studied. On the other hand, this pattern in frequency of occurrence might just be a consequence of populations of limpets being more crowded on seawalls because of the smaller intertidal extent.

On the other hand, P. vulgata shows a high tenacity to the substratum of up to 5.1 kg/cm2 which is helped by the production of mucus (Branch & Marsh, 1978). This might explain its common presence on the studied vertical seawalls where the presence of other grazers (i.e. snails) is more sparse; those snails might have more difficulties to stand on vertical surfaces in comparison to limpets (Díaz-Agras, unpublished results). Therefore, this intrinsic ability of this limpet could suppose an advantage in terms of interspecific competition and, in turn, to contribute to a different structuring of intertidal assemblages on seawalls. On the contrary, standing on vertical surfaces might translate in more energy dedicated to attach to the substratum and this can be affect to the biological performance of limpets on seawalls (maximal sizes attained, reproductive output, survival) when compared to those of populations on natural horizontal rocky shores (Branch, 1981).

Table 3: Summary of contingency tests for comparisons of frequency of occurrence of Patella vulgata among seawalls (SW) and rocky

shores (RS) at midshore and lowshore levels. ns, not significant (p>0.05); *p<0.05; ** p<0.01.

89


In fact, there seem to be differences on length-frequency distribution among populations on seawalls and rocky shores. Thus, greater sizes were observed on rocky shores (>30 mm in length) although this pattern was not true for all stations. Moreira et al. (2006) showed that populations of the pulmonate limpet, S. denticulata, on vertical seawalls are composed by juveniles and small adults and that reproductive output of those are smaller than on populations on rocky shores. In our case, it is not known yet whether the reproductive output of P. vulgata differs among natural and artificial habitats. Smaller adults of gastropods in general, and of limpets, in particular, have a smaller reproductive output than larger specimens (Creese, 1980; Valentinsson, 2002; Moreira et al., 2006). This fact has an important implication in maintenance of populations on seawalls. Thus, if animals on seawalls have a smaller reproductive output and produce few larvae, maintenance of their populations in the artificial habitat will depend on the existence of viable populations on natural habitats (Moreira et al., 2006). That way, reduction or fragmenting of rocky shores at expenses of artificial structures could translate in a potential risk for survival of local populations, and, in turn, in the structuring of intertidal assemblages and in a loss of biodiversity. In addition, alterations in composition assemblages may facilitate the spread of invasive species, which in many cases have a negative impact in survival of local species (Vaselli et al., 2008).

In conclusion, further experimental work is needed to test the patterns found here. Furthermore, reproductive output, competitive interactions and grazing behaviour of P. vulgata should be studied and compared among natural and artificial habitats in order to understand the value of seawalls as a surrogate habitat for this limpet.

ACKNOWLEDGEMENTS

The authors want to express their gratitude to the staff of the Estación de Bioloxía Mariña da Graña for their help during field work and to J. García-

Carracedo who kindly revised the English version of the manuscript. Two anonymous referees provided useful comments which contributed to improve the final version of the manuscript.

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93

DISTRIBUTION AND ECOLOGICAL ANALYSIS OF THE SYLLIDAE (ANNELIDA, POLYCHAETA) FROM THE ENSENADA

DE SAN SIMÓN (GALICIA, NW SPAIN)

ABSTRACT

Syllids (Annelida: Polychaeta: Syllidae) are one of the most diverse and numerically dominant polychaete taxa on marine benthic assemblages. In this paper, the distribution, diversity and composition of syllid assemblages at the soft bottoms of the Ensenada de San Simón (north-western coast of Spain) is studied by means of quantitative sampling. Sampling was done at 29 stations (8 intertidal and 21 subtidal). A total of 1057 individuals belonging to fourteen species were collected. Syllids showed the highest number of species and total abundance at subtidal sediments, and were rare in intertidal areas. The numerically dominant species in subtidal bottoms were Sphaerosyllis hystrix and Parexogone hebes. Depth, finer granulometric fractions and calcium

carbonate were the most important abiotic factors in determining the patterns of distribution of the syllids in the Ensenada de San Simón. In general, syllid diversity was lower than in other Galician rias which have a greater sedimentary diversity.

INTRODUCTION

The Syllidae constitute a large family of small polychaetes comprising more then 700 valid species and 70 genera (Aguado & San Martín, 2009). They have a wide range of feeding habits (Fauchald & Jumars, 1979; Giangrande et al., 2000) and live in cryptic places, moving around actively on the surface of the substrate. They have been reported on a great variety of substrates such as macrophytes and mangroves (Russell, 1989; López et al., 1997), sponges and corals (San Martín, 1991; Pascual et al., 1996), being particularly diverse and abundant in rocky environments (Bone & San Martín, 2003; Serrano et al., 2006) and in soft bottoms as well (Granados-Barba et al., 2003; Moreira et al., 2006). In fact, the family frequently represents the most abundant and diversified group within polychaete collections.

(1) Departamento de Ecoloxía e Bioloxía Animal,Facultade de Ciencias do Mar, Universidade de Vigo,E-36310 Vigo, Spain. e-mail: [email protected]

(2) Estación de Bioloxía Mariña de A Graña,Universidade de Santiago de Compostela,E-15590 A Graña, Ferrol, Spain.

Key words: macrofauna, Syllidae, subtidal, sediment, spatial distribution, biodiversity, Ensenada de San Simón, Atlantic Ocean.

EVA CACABELOS(1), JUAN MOREIRA(2) & JESÚS S. TRONCOSO(1)

94

EVA CACABELOS, JUAN MOREIRA & JESÚS S. TRONCOSO

The taxonomy and ecology of the macrobenthic assemblages inhabiting intertidal and subtidal soft bottoms of the Galician coasts have extensively been studied in the last years (e.g. López-Jamar, 1978; Mora, 1982; Junoy, 1996; Moreira et al., 2006; Lourido et al., 2008). The benthic assemblages of the Ensenada de San Simón have previously been studied as a whole (Cacabelos et al., 2008),

but the structure and composition of the syllid assemblages have not been exhaustively quantified yet. Therefore, the aim of the present study is to describe the diversity and assemblage structure of the syllids inhabiting intertidal and subtidal soft substrata at the Ensenada de San Simón, as well as to determine which are the main abiotic factors structuring their populations.

16

12

3

45

6

78 9 10

11 12 13 14 15

16 17 18 19 20

24

26 29

Río Oitabén-Verdugo

PONTESAMPAIO

SOUTOXUSTO

REDONDELA

1 K

m

N

5

15 10

22 2523

282721

Río XunqueiraRí

oA

l ve d

osa

Iberian Peninsula Ria de

Vigo

Ensenada San Simón

Ria deVigo

8º 36’ W10 K

m

N

42º 18’ N

FIGURES

Figure 1. Location of the Ensenada de San Simón and distribution of the sampling sites.

Eliminado: <sp>

Figure 1: Location of the Ensenada de San Simón and distribution of the sampling sites

95

DISTRIBUTION AND ECOLOGICAL ANALYSIS OF THE SYLLIDAE (ANNELIDA, POLYCHAETA)FROM THE ENSENADA DE SAN SIMÓN (GALICIA, NW SPAIN)


Study area The Ensenada de San Simón is located in the

inner part of the Ria de Vigo, between 42º 170 and 42º 210 N and 8º 370 and 8º 390 W (Figure 1). Soft-bottoms of this inlet are mainly muddy with high organic matter content (Vilas et al., 1995). Intertidal and shallow subtidal areas have meadows of the seagrasses Zostera noltii Hornem. and Z. marina L. Culture of mussels on rafts is a common practice in large areas at the mouth of the inlet. Large freshwater input occurs in the innermost part of the inlet which translates into fluctuations of salinity on both a tidal and seasonal basis (Nombela & Vilas, 1991).

Sampling design Benthic samples were collected in November-

December 1999 from 29 sites (Figure 1). Five replicate samples were taken at each site with a van Veen grab (0.056 m2); samples were sieved through 0.5 mm mesh. Retained material was fixed in 10% buffered formalin. Fauna was sorted in the laboratory, preserved in 70% ethanol and identified to the species level. Temperature and pH were measured in situ from water and sedimentary samples taken from each site. An additional sedimentary sample was taken at each site for grain-size analyses (content in granulometric fractions (%), median grain size, sorting coefficient, skewness) and to determine content of calcium carbonate and total organic matter (see for details Cacabelos et al., 2008).

17

Figure 2. Spatial distribution and densities of the numerically dominant syllid species

at the Ensenada de San Simón.

1 - 4950 - 99100 - 499> 500

Densities of

(Ind m-2)Sphaerosyllis hystrix

1 - 910 - 4950 - 199> 200

Densidades de

(Ind m-2)Parexogone hebes

Eliminado: <sp>

Figure 2: Spatial distribution and densities of the numerically dominant syllid species at the Ensenada de San Simón.

96


Data analysis

Total abundance of each species was determined for each site. Syllid assemblages were characterized through non-parametric multivariate techniques using the Plymouth Routines in Multivariate Ecological Research software package (PRIMER; Clarke & Warwick, 1994). A similarity matrix was prepared using the Bray-Curtis coefficient (Bray & Curtis, 1957) after applying the fourth-root transformation to the species abundance. Data were previously averaged across the five replicates for each site thus obtaining a centroid. Classification and ordination of the sites was done by cluster analysis through the algorithm UPGMA and non-metrical multidimensional scaling (MDS), respectively. The SIMPER program was used to identify species that contributed to dissimilarity among groups of sites determined by classification and ordination analyses. Relationships between abundance of syllid species and environmental variables were investigated by means of the BIOENV procedure (PRIMER package). Environmental variables expressed in percentages were previously transformed by log (x + 1) and then all of them were normalized.

RESULTS

Sedimentary characterization

Sediments of the Ensenada de San Simón were characterized by a predominance of silt/clay with high content of total organic matter and low content in calcium carbonate. Sandy sediments were present in tidal channels at the inner part of the inlet where low content of total organic matter was also found. Areas around the outer part of the inlet had muddy sands with a great content in gravel; the latter was comprised of empty shells of mussels which are cultured there on rafts. During the samping, alive bundles of Zostera noltii appeared in sites 2 and 3, and Z. marina plants were collected in sites 1, 2, 3, 10 and 20.

Species distribution and abundance

A total of 1057 individuals were collected, of which 6.91% was found in intertidal areas and 93.09 % in subtidal sediments. Fourteen taxa were identified to the species or genus level, representing 7 genera (Table 1). Five species were identified from intertidal

18

100

80

60

40

20

0

Similarity(%)

29 20 12 252824 139 2622 2119 181423 271716 51510 7 11864

BA

A2 A1

Figure 3. Hierarchical clustering of samples (centroids) based on fourth-root

transformed data of syllid abundance and Bray-Curtis similarity index.

Eliminado: <sp>

Figure 3: Hierarchical clustering of samples (centroids) based on fourth-root transformed data of syllid abundance and Bray-Curtis similarity index.

97


bottoms and 14 from subtidal areas; only 4 species were found from the intertidal to the subtidal zone. The dominant species in intertidal sediments were Parapionosyllis brevicirra Day, 1954 (5.30% of total abundance) and P. minuta (Pierantoni, 1903) (1.23%), whereas Sphaerosyllis hystrix Claparède, 1863 (49.67%), Parexogone hebes (Webster and Benedict, 1884) (33.40%) and E. naidina Örsted, 1845 (5.30%) dominated in subtidal bottoms.

The taxa Myrianida sp., Myrianida cf. edwardsi (Saint-Joseph, 1887), Procerarea sp., Sphaerosyllis websteri Southern, 1914, Eunaceusyllis belizensis (Russell, 1989), Prosphaerosyllis campoyi (San Martín, Acero, Contonente and Gómez, 1982), Syllides cf. edentatus (Westheide, 1974), Syllis columbretensis (Campoy, 1982) and S. gracilis Grube, 1840 were found in low numbers along the inlet.

19

Figure 4. Dendrogram based on cluster analysis showing the classification of species in

the study area.

100806040200

Procerarea sp.

Parapionosyllis minuta

Syllis columbretensis

Parapionosyllis brevicirra

Syllis gracilis

Myrianida edwardsicf.

Erinaceusyllis belizensis

Streptosyllis websteri

Prosphaerosyllis campoyi

Exogone naidina

Parexogone hebes

Sphaerosyllis hystrix

Syllides edentatus cf.

Myrianida sp.

Similarity (%)

1b

1a

2

Eliminado: <sp>

Figure 4: Dendrogram based on cluster analysis showing the classification of species in the study area.

98


Parexogone hebes appeared distributed all over the inlet, at a wide range of depth and sediments; the highest densities were detected in the central channel of Ensenada de San Simón at bottoms deeper than 10 m (Figure 2). The organic matter content at those sediments was of between 10.60% and 19.78%, and the calcium carbonate content ranged from 2.28% to 8.61 %. The abundance of this species was positively correlated with that of S. hystrix (rs: 0.794, p<0.01). Exogone naidina also appeared widely distributed at the Ensenada de San Simón but densities never exceeded 50 individuals per m2. This species appeared in all types of sediments but did not show any significant correlation with the considered sedimentary parameters.

Parapionosyllis brevicirra was only found at two sampling sites reaching densities up of to 195 individuals per m2 at sandy intertidal areas. The abundance of this species showed a positive significant

correlation with the content of coarse sand (rs: 0.751, p<0.01). The other species of the genus found at the inlet, i.e. P. minuta, also appeared in intertidal areas characterized by coarse sediments, showing a positive correlation with mean grain size (rs: 0.751, p<0.01). In general, this species was found in sediments with low contents in organic matter (0.95-4.90%) and calcium carbonate (6.00-11.98%).

Among the genus Sphaerosyllis, S. hystrix was the more abundant species and appeared from intertidal to deep subtidal sites, in sediments ranging from muddy sand to mud. Its highest densities were found at the mouth of the inlet in deeper bottoms of muddy sand. At those sites, content in organic matter and calcium carbonate ranged from 7.22% to 19.7 % and between 2.28% and 40.46%, respectively. The abundance of S. hystrix was highly correlated with depth (rs: 0.887, p<0.01).

20

TABLES

Table 1: List of syllid species and summary of abiotic characteristics of the sediments at the Ensenada de San Simón in which each species was

found (values: range). Q50, Median grain size; GR, Gravel; OM, Organic matter content; CO3, Calcium carbonate content.

Q50 (mm) GR (%) Sand (%) Silt/Clay (%) Depth (m) OM (%) CO3 (%)

Eunaceusyllis belizensis 0.008-1.500 0.00-40.17 2.33-48.34 11.49-97.67 2.9-28.2 7.22-36.93 4.28-40.46

Exogone naidina 0.008-1.500 0.00-40.17 2.33-94.47 2.12-97.67 1.6-28.2 1.0-36.93 2.12-40.46

Myrianida cf. edwardsi 0.008-1.500 0.00-40.17 2.33-73.99 8.22-97.67 1.16-28.2 2.16-36.93 4.28-40.46

Myrianida sp. 0.011 1.254 25.15 73.6 5.9 22.2 5.4

Parapionosyllis brevicirra 0.740-1.500 3.49-40.17 48.34-94.39 2.12-11.49 1.8-28.2 1.00-7.22 8.35-40.46

Parapionosyllis minuta 0.320-1.250 17.79-29.96 64.36-76.83 2.05-8.22 1.6-1.8 0.95-4.90 6.00-11.98

Parexogone hebes 0.008-1.500 0.00-40.17 13.94-48.34 11.49-86.06 2.0-28.2 7.22-23.00 2.28-40.46

Proceraea sp. 0.008 0.95 15.48 83.57 4.2 21.47 4.53

Prosphaerosyllis campoyi 0.010-1.500 0.63-40.17 19.97-48.34 11.49-78.05 2.9-28.2 7.22-23.00 2.28-40.46

Sphaerosyllis hystrix 0.005-1.500 0.00-40.17 12.59-77.69 10.48-87.41 1.6-28.2 1.80-23.72 2.12-40.46

Streptosyllis websteri 0.013 1.03 37.38 61.59 10.4 12.98 5.51

Syllides cf. edentatus 0.010-0.015 0.00-9.30 13.94-37.38 61.59-86.06 3.7-11.5 10.60-22.17 4.53-8.61

Syllis columbretensis 0.008 - 2.33 97.67 2.9 36.93 4.28

Syllis gracilis 0.010-1.500 0.00-40.17 13.94-48.34 11.49-86.06 4.7-28.2 7.22-21.05 4.53-40.46

Eliminado: <sp>

Table 1:List of syllid species and summary of abiotic characteristics of the sediments at the Ensenada de San Simón in which each species was found

(values: range). Q50, Median grain size; GR, Gravel; OM, Organic matter content; CO3, Calcium carbonate content.

99


Syllid assemblages and environmental analysis

The cluster analysis showed the presence of two major groups of sites at a similarity level of 30% (Figure 3): Group A (subtidal bottoms) and Group B (intertidal sediments). At a similarity level of 50 %, group A can be divided in two groups (A1 & A2). The physical characteristics of the three assemblages are detailed in Table 2.

SIMPER test showed that Exogone naidina was

the most representative taxa within Group B (average similarity: 35.36%). For group A1 (average similarity: 60.52%), Sphaerosyllis hystrix and P. hebes were the most characteristic species; group A2 (average similarity: 57.68%) was characterized by S. hystrix. Groups A1 and B showed an average dissimilarity of 91.66 %; S. hystrix and P. hebes were the species that more contributed to the dissimilarity. In the case of groups A1 and A2 (average dissimilarity: 71.82%), S. hystrix and P. hebes were the species most contributing to dissimilarity. On the other hand, S. hystrix, E. naidina, Parapionosyllis brevicirra and P. minuta were the most important species contributing to the dissimilarity among groups A2 and B (average dissimilarity: 76.48%).

Cluster analysis done on abundance data to determine affinities among species showed two main groups of species (Groups 1 and 2; Figure 4). Group 1 can be divided in two groups (1a & 1b): Group 1a was comprised of species mostly found at muddy subtidal bottoms (sites 17, 19, 21-23, 26-27), namely

Streptosyllis websteri, Syllides cf. edentatus and Syllis gracilis. Group 1b was comprised of Sphaerosyllis hystrix, Prosphaerosyllis campoyi, Parexogone hebes and E. naidina; those species were shared by site groups A and B and were found in high densities at sampling sites located along the subtidal areas of the inlet. Group 2 of species consisted of rare species mostly found at shallow or intertidal sites located at

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Table 2: Summary of physical characteristics of the three syllid assemblages

determined by multivariate analyses (values: mean ± standard deviation). Q50, Mediam

grain size; GR, Gravel; OM, Organic matter content; CO3, Calcium carbonate content.

Q50 (mm) GR (%) Sand (%) Silt/Clay (%) Depth (m) OM (%) CO3 (%)

A1 0.16±0.47 6.71±12.16 27.03±10.25 66.26±21.02 9.57±7.98 16.89±5.13 8.64±11.29

A2 0.04±0.08 3.72±4.22 30.14±21.88 66.15±25.83 3.31±1.06 18.62±7.66 3.97±1.26

B 0.43±0.55 6.75±16.15 48.85±41.00 44.40±46.56 2.70±0.86 14.66±16.07 6.22±1.70

Eliminado: <sp>

Con formato: Fuente: Negrita

Table 2:Summary of physical characteristics of the three syllid assemblages determined by multivariate analyses (values: mean ± standard deviation). Q50,

Mediam grain size; GR, Gravel; OM, Organic matter content; CO3, Calcium carbonate content.

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Table 3: Combinations of n variables showing the highest avlues of Spearman rank

correlations (�w) between biotic (Bray-Curtis similarities) and abiotic (Euclidean

distances) similarity matrices. FS, Fine sand; VFS, Very fine sand; CSi, Coarse silt;

Fsi, Fine silt; C, Clay; CO3, calcium carbonate; Sk, skewness.

n �w Variables

5 0.470 FS, VFS, CSi, C, CO3

FS, VFS, CSi, CO3, Sk

0.467 FS, VFS, CSi, FSi, CO3

0.466 AM, VFS, CSi, C, Sk

FS, VFS, CSi, FSi, C

0.465 FS, VFS, CSi, C, Sk

0.464 VFS, CSi, C, CO3, Sk

4 0.469 FS, VFS, CSi, CO3

FS, VFS, CSi, C

0.467 FS, VFS, CSi, FSi

VFS, CSi, CO3, Sk

0.465 VFS, CSi, C, CO3

3 0.465 VFS, CSi, CO3

FS, VFS, CSi

0.464 VFS, CSi, Sk

Eliminado: <sp>

Con formato: Fuente: Negrita

Table 3:Combinations of n variables showing the highest values of Spearman rank correlations (ρw) between biotic (Bray-Curtis similarities) and

abiotic (Euclidean distances) similarity matrices. FS, Fine sand; VFS, Very fine sand; CSi, Coarse silt; Fsi, Fine silt; C, Clay; CO3, Calcium

carbonate; Sk, Skewness.

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the inner area of the inlet (sites 4, 8, 10 and 15), and in the deepest sites (21 and 26), namely Erinaceusyllis belizensis, Myrianida cf. edwardsi, Syllis gracilis and Parapionosyllis brevicirra.

The matching of the environmental and syllid abundance matrices (BIOENV analysis) is outlined in Table 3. No single variable provided the best correlation with biotic patterns. The combinations of variables that best explained the faunal structure were those composed by the finer granulometric fractions and calcium carbonate.

DISCUSSION The numerical contribution of the syllids to the

total polychaete fauna of San Simón was small (4.3 % only). This percentage is quite low when considering that this family frequently represents an abundant and diversified group within many polychaete collections from shallow subtidal soft-bottoms. In general, our study showed lower values for total number of species and abundance when compared to data from other areas located in the Ría de Vigo (e.g. Moreira et al., 2006) and nearby rias. Thus, Moreira et al. (2006) and Lourido et al. (2008) reported respectively 26 and 28 species from the Ensenada de Baiona (Ría de Vigo) and the Ensenada de Aldán (Ría de Pontevedra). Those areas are characterized by a greater variety of sediments (ranging from gravel to mud) than that present at the Ensenada de San Simón; the latter was characterized mostly by muddy sediments. In fact, syllids are diverse and numerically dominant at the coarse and medium-sand sediments present at the oceanic-influenced outer areas of the rias de Vigo and Pontevedra. Clean sandy sediments located at areas exposed to oceanic swell at the mouth of the Galician rias have low content in silt/clay (López-Jamar & Mejuto, 1985; Troncoso & Urgorri, 1993) and have more interstitial spaces available; this particular granulometry provides with more microhabitats for small, cryptic polychaete fauna than the muddy and more homogenous sediments present at the Ensenada de San Simón.

Most of the total syllid abundance was due to the numerical contribution of Parexogone hebes and Sphaerosyllis hystrix. The former is an ubiquitous species reported from a number of habitats both intertidal and subtidal, such as seagrass meadows, sediments ranging from mud to coarse sand, and environments with low hydrodynamic as well (e.g. Sardá, 1987; Parapar et al., 1996). Parexogone hebes has been reported along most of the Galician coast, from the Ría del Eo to the Ensenada de Baiona (Parapar et al., 1996; Moreira et al., 2006; Lourido et al., 2008). Similarly, Sphaerosyllis hystrix is regarded as a widespread species found in subtidal hard substrata, “maërl” bottoms, seaweeds, seagrasses and sandy sediments. Our findings are in agreement with the observations of Martín (1986), who regards S. hystrix as a subtidal species; on the contrary, Parapar et al. (1996) only found this species at the Ría de Ferrol in intertidal habitats. This species is widespread along many of the Galician rias (Parapar et al., 1996; Moreira et al., 2006).

Syllids were absent, in general, from the intertidal

areas of the Ensenada de San Simón, apart from site 15, which was characterized by a high content in sandy fractions and also by containing shells of cockles and gastropods. Curiously, at those areas Sphaerosyllis hystrix was only represented by a small number of individuals.

On the other hand, the syllid fauna of the Zostera meadows at the inner part of the Ensenada de San Simón was poorer than those recorded from other bare areas of the inlet with similar sedimentary composition, in similar habitats of Galician coasts (Quintas, 2005) or along the world (i.e. other seagrass meadows). For example, Lanera & Gambi (1993) and Gambi et al. (1995) reported respectively 19 and 34 syllid species from Cymodocea nodosa and Posidonia oceanica meadows at the Mediterranean Sea, while only 5 were collected in Zostera marina meadows at San Simón. In other cases, high number of species and

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densities of syllids have also been recorded living both on the leaves and rhizomes of Posidonia oceanica (San Martín et al., 1990; Somaschini et al., 1994), Zostera spp. (Hutchings, 1981), Halodule wrightii (Nelson & Capone, 1990) and Thalassia testudinum (Stoner & Lewis, 1985). This highlights the importance of the Syllidae among the polychaetes associated to seagrass meadows. The relative scarcity of syllids at the Ensenada de San Simón could be explained because sampling was done during autumn and in inner intertidal and shallow subtidal bottoms. There is a great temporal variability in the number of species and abundance of syllids in soft bottoms. For instance, Stoner (1980), San Martín et al. (1990) and Gambi et al. (1995) reported minimum values for those parameters in polychaete populations during the autumn. Nevertheless, other abiotic and biotic factors such as reproductive strategies, dispersion ability and temporal variation in hydrodynamics and granulometry should be taken into account to explain the patterns found here within a temporal scale (Bone & San Martín, 2003). Thus, the lack of a richer syllid fauna at the Ensenada de San Simón may also be related to the changes in salinity at the areas where the Zostera marina and Z. noltii meadows are present. In fact, large freshwater input f lows in the area for most of the year which can have a great impact in the survival and establishment of species there apart from those adapted to this changing environment, such as the cockle Cerastoderma edule, and the snail, Hydrobia ulvae. This would help to understand the patterns of distribution of the benthic fauna in the Galian rias in general and provide baseline data which would be useful for management and preservation of the marine biodiversity.

ACKNOWLEDGEMENTS

We are grateful to the members of the laboratory of Adaptaciones de Animales Marinos (Univ. Vigo) for their invaluable help with sample collection.

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López E, San Martín G, Jiménez M (1997). Two new species of Syllids (Polychaeta: Syllidae) from the Chafarinas Islands (Alborán Sea, SW Mediterranean). Bulletin of Marine Science 60: 293-299.

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Lourido A, Cacabelos E, Troncoso JS (2008). Patterns of distribution of the polychaete fauna in subtidal soft sediments of the Ría de Aldán (north-western Spain). Journal of the Marine Biological Association of the United Kingdom 88: 263-275.

Martín D (1986). Anélidos Poliquetos y Moluscos asociados a algas calcáreas. MSc Thesis, University of Barcelona.

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Quintas P (2005). Distribución espacial y temporal de los moluscos y anélidos poliquetos asociados a las praderas

de Zostera marina L. y Zostera noltii Hornem. en la Ensenada de O Grove (Galicia, España). PhD thesis, Vigo University, Galicia, Spain.

Russell DE (1989). Three new species of Sphaerosyllis (Polychaeta, Syllidae) from mangrove habitats in Belize. Zoologica Scripta 18: 375-380.

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Somaschini A, Gravina MF, Ardizzone GD (1994). Polychaete depth distribution in a Posidonia oceanica bed (Rhizome and Matte Strata) and neighbouring soft and hard bottoms. Marine Ecology 15: 133-151.

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Troncoso JS, Urgorri V (1993) Datos sedimentológicos y macrofauna de los fondos infralitorales de sustrato blando de la Ría de Ares y Betanzos. Nova Acta Científica Compostelana (Bioloxía) 4: 153-166.

Vilas F, Nombela MA, García-Gil E, García-Gil S, Alejo I, Rubio B, Pazos O (1995). Cartografía de sedimentos submarinos: Ría de Vigo. Memoria del Dpto. de Recursos Naturales y Medio Ambiente (Área de Estratigrafía) de la Universidad de Vigo. Ed. Xunta de Galicia. 40 pp.


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MESOZOOPLANKTON COMMUNITY STRUCTURE DURING SUMMER MONTHS IN THE BAY OF CÁDIZ

ABSTRACT

Mesozooplankton organisms (>250 μm) were sampled at two stations (inner and outer Bay) in the Bay of Cádiz between May and July 2008. Samples were analysed by means of a semi-automated technique in order to give a preliminary view of the mesoozooplankton community structure in the Bay, based on taxonomic diversity and biomass distribution among size classes. The abundance of organisms increased from May to July in accordance with the increase in temperature and Chlorophyll a (Chla) concentrations. Abundances were higher in

the outer Bay station, where Chla concentrations are greater and the water column is more stable. The community changed from being meroplankton- to holoplankton-based due to an increase of Calanoida and especially Cladocera individuals (mainly Penilia avirostris), which are known to peak acutely in the summer. The analysis of Normalised Biomass-Size spectra revealed fairly steep slopes (average -1.3) and relatively high departures from steady state (r2 = 0.8 – 0.94), expectable in a coastal system such as the Bay of Cádiz were disturbance factors are introduced from benthic and tidal processes, together with anthropogenic pressure.

INTRODUCTION

The growing consciousness on the role of coastal areas in global CO2 budgets has lead scientists to initiate diverse research programmes covering various issues (Siefert and Plattner, 2004). Much discussion has awoken around the controversy on whether these ecosystems are acting as sources or sinks of the greenhouse gas. In this context, the present study is part of the 2007 Excellence Projects Call, held by the Andalusian regional

Key words: Plankton Visual Analyser, biomass, size spectra, Bay of Cádiz.

MAR BENAVIDES(1,*), FIDEL ECHEVARRÍA(2), REYES SÁNCHEZ-GARCÍA(3), NATALIA GARZÓN(3) & JUAN IGNACIO GONZÁLEZ-GORDILLO(3)

(1) Departamento de Biología, Facultad de Ciencias del Mar, Campus Universitario de Tafira, 35017Las Palmas de Gran Canaria, Canary Islands, Spain

(2) Departamento de Biología, Facultad de Ciencias del Mar, Universidad de Cádiz, 11510 Puerto Real, Cádiz, Spain

(3) Centro Andaluz de Ciencia y Tecnología Marinas (CA-CYTMAR), Universidad de Cádiz, Av. República Saharaui s/n, 11510 Puerto Real, Cádiz, Spain

*Corresponding author:[email protected].: (+34) 928 454547

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MAR BENAVIDES, FIDEL ECHEVARRÍA, REYES SÁNCHEZ-GARCÍA, NATALIA GARZÓN & JUAN IGNACIO GONZÁLEZ-GORDILLO

government (Junta de Andalucía) named Project Bahía, which aims to elucidate the overall carbon budget of the Bay of Cádiz and to start off a continuous data series which will provide valuable information about the ecosystem state and evolution. The high diversity and eco-sociological interest of the Bay of Cádiz (declared Natural Park in 1989, birds protected area-Zona de Especial Protección para las Aves (ZEPA)- in 1993, protected area under Ramsar Convention in 2002), as well as its situation near the connection of the Atlantic Ocean and the Mediterranean Sea are reasons why the study of carbon balances here are important as a reference-system when comparing with similar coastal ecosystems and semi-enclosed bays in mid-

latitude coasts. The great biological productivity of the Bay (Muñoz-Pérez and Sánchez-Lamadrid, 1994) highlights the need of considering the function of planktonic communities and their dynamics within the pelagic system together with physical and environmental variables in order to obtain an integrative approach for the study of the overall carbon budget. Indeed, linking physic-chemical variables to zooplankton community dynamics was one of the great goals of GLOBEC (GLOBEC, 1997; Alcaraz et al., 2007). The key role performed by zooplankton species in transferring biomass from autotrophic organisms towards higher trophic levels as well as their influence in vertical particle fluxes make zooplankton studies indispensible in marine

Figure 1: Map of the area of study and sampling stations.

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ecological and biogeochemical research (Banse, 1995). Plankton are drifting, short-lived and non-exploitable organisms (with the exception of some aquaculture-targeted phytoplankton species), thus environmental changes are well and rapidly reflected on them. Hence, building planktonic community data series yields valuable proxies for climate change evidence (Hays et al., 2005).

Much effort has been invested in zooplankton dynamics studies and our knowledge has evolved considerably, but facts such as undersampling, time-consuming analysis and low spatial-temporal resolution remain a drawback (Grosjean et al., 2004), although the latter has been relatively solved with new sampling devices such as the Longhurst-Hardy Plankton Recorder (Longhurst et al., 1966) or the Video Plankton Recorder (Davis et al., 1992). Counting, identifying and measuring the size of zooplankton organisms are still tasks of crucial importance which unfortunately entail large efforts in time and previous taxonomic classification experience (Grosjean et al., 2004). The need to overcome this problem has led oceanographers and planktologists to develop automated methods based on image analysis (Rolke and Lenz, 1984). Although the effectiveness of plankton-imaging systems has been corroborated reporting accuracy levels up to 70-80% with 10-20 taxonomic classes (Benfield et al., 2007), it must be noted that these systems need good image-acquisition tools which often lead to high-resolution images. This increases the computer power requirements and, in most cases, does not allow identification to the species level. Nevertheless, these techniques have significantly reduced the sample-processing time and are especially useful regarding biomass estimates, as they do not involve the destruction of the samples by incineration or similar (Alcaraz et al., 2003).

In coastal ecosystems different taxa have been shown to be more or less abundant according to factors such as temperature, salinity, chlorophyll, nutrients and turbulence (Calbet et al., 2001; Lawrence et al.,

2004; Alcaraz et al., 2007), and throughout seasons (Fernández de Puelles et al., 2003; Isinibilir et al., 2008). Seasonal variability is especially distinctive for meroplankton species which only occur in certain parts of the year, when the environmental conditions are adequate for their development. As well, taking advantage of hydrodynamics is the strategy of many meroplankters, e.g. decapods that use tidal currents as a larval dispersion and recruitment method (Pineda, 2000). In our case of study, neighbouring areas such as the Gulf of Cádiz, Strait of Gibraltar and Mar de Alborán have been targeted in past studies concerning phytoplankton, bacterioplankton and especially ichthyoplankton due to the importance of fish landings in this area. Mesozooplankton has been well studied in Mar de Alborán, the Strait of Gibraltar and more scarcely in the Gulf of Cádiz. Within the Gulf, the Bay of Cádiz’s planktonic communities have been previously studied by Yúfera et al. (1984) who provided preliminary results on the zooplankton community composition within salt ponds of the marshes in the Bay, while González-Gordillo (1999), González-Gordillo and Rodríguez (2003) and González-Gordillo et al. (2003) presented comprehensive information on decapod larvae distribution and its assemblages’ ecology in the Bay and surrounding areas.

Surprisingly, the whole mesozooplanktonic community has not been sought in any previous studies of this system and therefore the aim of this work is to give a first estimation of the zooplankton community structure in the Bay of Cádiz. In our study, organisms are analysed by means of a semi-automated technique and the community structure is discussed based on taxonomic differences and biomass variability among size classes, in the frame of environmental factors variability, such as temperature, salinity, Chla and nutrients. The project’s perpetual monitoring-programme will provide a precious data series which will inform how climate change is affecting the structure of planktonic communities and the Bay’s ecosystem as a whole.

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Figure 2: Temperature, salinity and total Chla profiles for ST1, ST2 and ST3 between May and July 2008.

METHODS

Study site

The Bay of Cádiz is a shallow water coastal ecosystem in the SW of Spain composed of two basins (inner and outer bays) connected by a narrow navigation channel (figure 1). The area is subjected to a semidiurnal tidal regime which exerts great control on the ecosystem, providing water renewal rates of 30% during neap tides and 75% during springs (Álvarez et al., 1999). The vast extensions of intertidal zones and salt marshes surrounding the area produce nutrient and organic matter loading which together with the favourable light and temperature conditions make the Bay of Cádiz a productive ecosystem which houses a great variety of algae, seagrasses, as well as an important hatchery role for many fish and crustacean species (González-Gordillo and Rodríguez, 2003). Sampling was performed in the Bay of Cádiz at three stations in 3 cruises between May and July 2008 (12th May, 16th June and 1st July, correspondingly). Station 1 corresponds to the inner bay, station 2 is located in the narrow channel which connects both bays and station 3 corresponds to the outer bay (these stations will be referred to as ST1, ST2 and ST3 hereinafter).

Sampling procedures and seawater analysis

At each station temperature, salinity and fluorescence data were obtained with a SeaBird25 CTD making vertical profiles from surface to bottom. Transects were performed sailing from ST3 to ST1 logging surface fluorescence, temperature and salinity data each second at a mean speed of 6 knots. Seawater samples for nutrients and Chla analysis were taken with a Niskin bottle from the bottom and surface of the water column (depth varied depending on the tide height and station). Zooplankton was collected performing double-oblique tows at ST1 and ST3 with a Bongo net fitted with 250 µm mesh and equipped with an analogical flowmeter. The mean volume filtered was 59.3 m3, ranging between 27.4 and 74.6 m3. The net was rinsed gently and then samples were transferred

into 500 ml containers and finally preserved adding buffered formalin to a final concentration of 4%. Total Chla concentrations were obtained after filtering 250 ml on Whatman glass fibre filters (GF/F) and analysing them by means of a Turner fluorimeter. Seawater samples were analysed for nitrate, nitrite, phosphate and silicate with a segmented flow San++ Skalar Autonalyser, following the automated methods described by Grasshoff et al. (1983).

Counting and measuring zooplankton

Identification, counting and size measurements of zooplanktonic organisms were made by means of the Plankton Visual Analyzer (Boyra et al., 2005; PVA, 2005), a free plankton-imaging software available from AZTI’s website (www.azti.es). The software was used in its Visual Mode, which allows the user to extract individual size data from each of the organisms in a digital image. Before being processed, samples were concentrated and dyed with Rose Bengal for 24 hours to enhance contrast between the organisms and the background. Then they were filtered through 1000, 500 and 250 µm sieves and divided into 3 size fractions, namely >1000 µm, <1000 and >500 µm, <500 and >250 µm. Subsequently, each fraction was subsampled with 10 ml automatic pipette. Depending on the density of organisms in each fraction 4 to 8 subsamples were performed. Each subsample was placed in a Petri dish and previewed under a stereomicroscope with the purpose of removing any particles and separating organisms forming tangles as these could be mistakenly recognised by the PVA as a candidates. Also, any overlaps or image-cuttings were avoided (e.g. organisms at the edge of the dish), preventing problems which could hinder the accuracy of our data. After this pre-treatment, digital images were obtained using a regular scanner. Different resolutions were used according to the size fraction which was being scanned, commonly we used 1200 ppi for the >1000 µm fraction, 1800 ppi for the fraction corresponding to sizes between <1000 and >500 µm, and 2000 ppi for <500 and >250 µm one. The last fraction occasionally needed 2400 ppi.

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Before processing, the parameters of the PVA were set according to the size and resolution of each image acquired. The PVA recognises each organism by searching sufficiently contrasting bodies within a size range set by the user, i.e. minimum and maximum pixels to be recognised as a candidate. Thus, the number of pixels per mm needs to be changed consistently with images’ resolution. After these settings, the image was imported and processed, classifying organisms in the

main (most abundant) taxonomic groups: Copepoda (namely Calanoida, Cyclopoida and Harpacticoida), Cladocera, Appendicularia, Cirripedia (only larvae), Ostracoda, Decapoda (zoeal stages of Brachyura, Anomura and Caridea), Siphonophora, Euphasiacea, Mysidacea, Chaetognata, Hydromedusae, Amphipoda and Ascidiacea. Taxa abundance and individual Equivalent Spherical Diameter (ESD) were obtained from each image.

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Figure 3: Total abundance variability (ind/m3) among stations between May and July 2008.

Figure 4: Taxa abundance (ind/m3) recorded between May and July 2008. Please note the different scales used for each graph.

Data

Biomass analysis

Individual ESD of mesozooplankton was used to calculate biovolume from the volume of a sphere with r = ESD/2. The biomass of crustaceans was determined by the biovolume-to-carbon conversion factor provided by Alcaraz et al. (2003), while gelatinous mesozooplankton biomass was calculated with that of Parsons et al. (1984). Biomass and biovolume values were used to build Normalised-Biomass Size Spectra (NBSS), confronting mean biomass (mg C/m3) and biovolume intervals (mm3), ranging from the smallest to the biggest organism found in the sample set. NBSS (Platt and Denman, 1978) were constructed plotting the biomass in a specific size class (as biovolume) divided by the amplitude of each interval (normalised biomass) versus biovolume, on a double logarithmic scale:

where Bm is the total biomass per size class m (in mg C/m3), a and b are constants, and m is the size class interval (in mm3). Results are discussed based on the slope (b), y-intercept (a) and determination coefficient (r2) yielded by the linear fit of the spectra.

Indices

The next indices were calculated for each sample, using the equations shown below. As our samples were classified as general groups (see Methods), these have been used as taxonomic units for the application of the different indices. Margalef’s species richness index (d):

where S is the total number of groups and N the total number of organisms. Shannon-Wiener diversity index (H’):

where pi is the relative abundance of each group, calculated as the proportion of individuals of a given group to the total number of individuals in the community (ni/N). Pielou’s evenness index (J’) responds to the next expression:

and Simpson’s dominance index (D%) was calculated as:

Constancy (C%) was calculated from the number of times a group appears in a station related to the total number of samples taken at that station.

RESULTS

Hydrography

The CTD profiles (figure 2) showed a considerable homogeneity in the shallow and tidally-mixed Bay of Cádiz, evident for both temperature and salinity with some exceptions. The more saline character of the inner bay waters can be noticed (due to the acute evaporation in the inner bay related to low depths and intense sunlight year round). Total Chla concentrations were similar between surface and bottom waters throughout the sampling period, though increasing from the inner to the outer bay, and from May to July.

Taxa spatial and temporal variability

Throughout the study period the total abundance of sampled organisms (ind/m3) increased in both the inner and outer Bay stations. The overall abundance distribution (sum of all mesozooplankton organisms) at ST1 and ST3 (figure 3) reported similar values in May whereas an augment in ST3 in relation to ST1 occurred in June, being even more acute in July. By taxa (figure 4), the abundance of organisms was always higher in the outer bay (ST3) than in the inner ST1 with some exceptions in May and June

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(see figure 4) and especially in July, when Cladocera, Cirripedia and Anomura individuals in the inner bay outnumbered those of the outer bay. Nevertheless, taxa abundance spatial variability was not found to be statistically significant.

Among months, the lowest abundances were recorded in May. The most abundant taxa then were copepods from the order Calanoida (52.7 ind/m3) at

ST3, followed by Anomura and Caridea (26.52 and 23.07 ind/m3, respectively). The highest abundance in May for inner ST1 was that of Caridea (11.42 ind/m3). Below that abundance, all the rest of taxa considered in this study were witnessed with the exception of Siphonophora. Interestingly, the taxa Appendicularia, Euphasiacea, Mysidacea and Amphipoda, which appeared in this first survey were not recorded again, neither in June nor in

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Figure 5: Species richness (d), Shannon-Wiener diversity index (H’) and Pielou’s evenness (J’) evolution at ST1 and ST3 throughout the study period.

Figure 6: Total biomass variability (mg C/m3) among stations between May and July 2008.

July. In June the groups Calanoida, Cyclopoida, Cirripedia, Brachyura, Anomura and Caridea were present at both stations, being more abundant in the outermost ST3. A remarkably great abundance of Caridea in ST3 was observed, reaching 407.3 ind/m3. July was dominated by the presence of copepods from the order Calanoida with 761.79 ind/m3 at ST3. The abundance of Cladocera increased to a great extent in comparison to previous surveys, reaching a maximum of 432 ind/m3 at the inner station ST1 and 393.35 ind/m3 at the outer one. Temporal abundance variability was demonstrated for Cladocera, Cirripedia and Hydromedusae, all p<0.005. Gathering all three sampling months (table 1), the most dominant taxon at ST1 was Cladocera (43.46 D%), followed by Calanoida, Caridea and Cirripedia (as >10 D% taxa). A 100% constancy was reached by Calanoida, Cirripedia, Brachyura, Anomura, Caridea and Chaetognata. At ST3, Calanoida were dominant (33.74 D%), closely followed by Caridea (22.76 D%). Cladocera also made up a considerable part of the mesozooplanktonic community in these months, with a dominance percentages >10%. A 100% constancy was achieved by Calanoida, Cladocera, Cirripedia, Brachyura, Anomura and Caridea.

The Holoplankton/Meroplankton ratio tem-poral evolution was calculated, resulting in a holoplanktonic dominance from May to June (0.81 and 0.50, respectively), which shifted in July to a predominantly meroplanktonic community (3.53). A general decrease in diversity was observed between May and July for both stations and linked to a drop in groups richness, though a slight increase in diversity occurred at ST3 in June (figure 5). Evenness maintained similar values from May to July in ST1, being more variable in ST3 where a small increase was followed by an acute decrease attributable to the augment of calanoids and cladocerans over the rest of taxa.

Biomass variability and distribution among size classes

Comparing the spatial distribution of total biomass (figure 6) to that of abundance (figure 3) it can be clearly seen that these two variables did not evolve in the same manner. The greater biomasses were found in May, when the lowest abundances occurred. This was caused by the presence of bigger organisms such as large brachyuran zoeas and anomurans, with

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Figure 7: Biomass distribution (mg C/m3) among functional groups for both stations between May and July 2008 (sum of all size fractions).

large biovolumes and low abundances of smaller holoplankters. In June and July, albeit abundances were not equal, biomasses maintained similar values among stations, meaning that mean biovolumes were minor due to the increased abundance of cladocerans and small calanoid copepods. The biomass provided by each taxon during the sampling period is shown in figure 7. In May, though the abundance of calanoid copepods was much higher at ST3 (figure 4), biomass was almost equal, it follows then that calanoid copepods from ST1 were more voluminous. This pattern in Calanoida biomass was observed in June too, though with much lower values. Their biomass increased again in July especially that of ST3, this time corresponding to a greater abundance.

Cladocerans’ biomass increased greatly during the sampling period, consistently with their abundance rather than with their size (biovolume), which was always similar (data not shown).

Cirripedia maintained similar abundances across months with only lower values at ST1 in May and ST3 in July due to lower abundance. The increase of biomass and steadiness in Brachyura abundance reflects their enlargement in size from May to June. Interestingly, this group increased in abundance in July maintaining similar biomass values. Anomura presented great differences between the inner and outer Bay biomass values in May (ST1 ones were so small that cannot even be noticed in the graph due to scale range). Their greatest biomasses occurred in June, being greater at ST1 and almost equal for both stations in July. The biomass of Caridea decreased from May to July, though a remarkable peak occurred at ST3 in June, related to a greater abundance (figure 4).

Concerning size classes, the mesh size used (250 µm) selects organisms with ESDs over that size. This selectivity should avoid the presence of smaller

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Figure 8: Biomass distribution among size classes at both stations throughout the study sampling period.

individuals but in our study their biomass appeared have similar values than the bigger zooplankters at the right hand side of the distribution (figure 8). This was due to the recurrence of “zooplankton tangles” (i.e. groups of attached organisms together with seagrass portions and other rests of organic matter), and also the abundance and biomass of these small organisms might be undersampled. The NBSS results are presented in table 2 (temporal variability among stations) and the overall spectra (average of all months) are plotted in figure 9. A greater temporal variability in slope was observed at ST3, as well as lower determinations coefficients in comparison with ST1. The over-time spectra for both stations though revealed similar departures from steady state (r2). Smaller undersampled classes were removed (0.002 to 0.008 mm3) and thus do not appear in the spectra. A steeper slope was computed for ST3, as well as the absence of some size classes which instead were present at ST1.

DISCUSSION

Taxonomic distribution

Plankton community structure studies are usually based on at least one-year data series. Although a three-month survey might not be sufficiently representative, the present work provides a first characterisation of the mesozooplankton community and its structure in the Bay of Cádiz, based on predominant groups. The image-analysis software employed offered an easy and rapid way to identify, count and measure zooplanktonic organisms, although it did not permit identification to the species level with common resolutions. Nevertheless, when necessary, previous observation under the stereomicroscope and pictures permitted the observation of some characteristic taxa which varied in space and time according to hydrographic features. The spatial significant differences in temperature support the variability

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Figure 9: NBSS representation for ST1 and ST3 (sum of May, June and July).

of abundance and taxonomic composition of zooplankton found, together with the increasing Chla concentrations occurred from the inner to the outer bay. Overall zooplankton abundance increased from May to July. The reduced abundance of zooplankters in May is not only attributable to colder temperatures,

but also to the remarked presence of ctenophores which may have been feeding on them actively. In addition, surface circulation patterns of tidal currents in the Bay of Cádiz (figure 7 in González-Gordillo and Rodríguez, 2003) probably play an important role on zooplankton distribution. In particular they

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Table 1: Total abundance (N, ind/m3), dominance index (D%) and constancy index (C%) for stations 1 and 3 throughout the study period.

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might be responsible for the greater abundances found in the outermost ST3 as the ebb flow passes by the area where ST3 is located and has a lower hydrodynamic activity and therefore houses warmer waters which are preferable for the development of most coastal zooplankton species. Moreover, Chla concentrations are greater in the outer bay than in the inner one where high turbidity levels might be hindering photosynthesis and consequently reducing autotrophic biomass.

Besides the short sampling period, sampling between May and July permitted us to witness the change from a meroplankton-based community to a holoplankton-based one. Meroplankters maintained similar abundances in June and July, therefore the ratio shift occurred in accordance with an augment of Calanoida and Cladocera species, rather than with a drawdown of meroplankton. This agrees with González-Gordillo and Rodríguez (2003) investigations, in which they found several peaks of meroplankton between spring and summer, up to August when the

environmental conditions are favourable for their development. Indeed, meroplankters found in this study (Cirripedia, Anomura, Caridea and Brachyura) showed a 100% constancy at both stations throughout the sampling period. From this we conclude that meroplankters make up a significant part of the zooplankton community in the Bay of Cádiz in the spring-summer period. Certainly, large abundances were found before (Rodríguez et al., 1997; Drake et al., 1998) and related to the absence of temperature and salinity abrupt changes in the Bay and associated to the semidiurnal regime and its high water renewal rates (Álvarez et al., 1999), which enhances the successful development of these species. The density of meroplankton species was greater in ST3 than in ST1, with the exception of Cirripedia and Anomura which were more abundant in the inner Bay. The remarkable abundance of Caridea at ST3 in June decreases towards July coinciding with the inter-spawning period of Philocheras (the most representative caridean taxon for this time in Cádiz Bay) and the shift of these species from planktonic

Table 1: Total abundance (N, ind/m3), dominance index (D%) and constancy index (C%) for stations 1 and 3 throughout the study period.

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to benthic life (González-Gordillo and Rodríguez, 2003). The drop of Anomura biomass from May to July is clearly identified with a decrease in size. Individuals in May were voluminous (mean of 0.65 mm3) and mixed with smaller ones, meaning various developmental stages are coexisting as this taxon peaks along all summer. In spring-summer months, the overall holoplankton taxa composition in the Bay is shared with that of the Gulf of Cádiz (Mafalda et al., 2007), though some groups found over the shelf are scarce here. The absence of gelatinous groups such as doliolids and siphonophores may be an advantage for copepods which are usually heavily preyed on by them.

Zooplankton species usually present a developing delay with respect to phytoplankton. Spring phytoplankton bloom typically occurs in April-May in the Bay of Cádiz (Establier et al., 1990) and therefore copepods (and other taxa) present higher abundances in June and July. The dominant copepods from the order Calanoida were more abundant at ST3 where Chla concentrations are greater. The absence of cyclopoids could be attributable to the inappropriate selectivity of the size mesh used (250 µm), as many of these species, such as Oithona sp. for instance, are smaller and important in coastal areas (Calbet et al., 2001). Calanoids were always more abundant at ST3 where the salinity was slightly lower due to the discharge of the Guadalete river (which is reduced, but not negligible), and always lower in comparison to the low depths of the inner bay. The calanoid group was mainly composed of Acartia and Paracalanus species known for being sensitive to salinity (Lawrence et al., 2004). Short-term seasonality is obvious as the total abundance of organisms increases with temperature from May to July. In particular, the cladoceran Penilia avirostris, known for presenting abundant blooms due to their rapid parthenogenetic reproduction, are habitually used as a biological indicator of warmer waters. These cladocerans abounded in the Bay of Cádiz in July as it occurs in other parts of the south-Iberian and Mediterranean Seas (Calbet et al., 2001; Mafalda

et al., 2007). The temperature increase may have been responsible for the absence of Chaetognata in June and July, as this rather oceanic taxon prefers colder waters.

Biomass distribution

The flow of biomass occurs through size-dependent processes in trophic food webs, therefore the distribution of biomass among size classes follows regular patterns (Sheldon et al., 1972) that are superimposed on species diversity. Thus, the construction of NBSS yields an easy way to aggregate and compare the large amounts of individualised information given by imaging systems, as size and biomass are properties present upon all taxa (Parsons, 1969). In this sense, the use of this type of spectra provides a comparative approach for planktonic community structure analysis regardless of taxonomic differences between organisms (Quiñones et al., 2003). The analysis of the NBSS constructed for ST1 and ST3 demonstrated differences among them, based on the distribution of biomass among size classes rather than on taxonomic composition. The greater abundance of organisms at ST3 is reflected in the larger y-axis intercept of its NBSS, as this is indicative of abundance. As well, disturbances external to the pelagic system such as benthic and near-shore interactions are reflected in the NBSS as departs from steady state and thus variation around the linear trend is found (Sprules and Manawar, 1986).

The Bay of Cádiz is subject to a great variability due to hydrodynamic activity and anthropogenic pressure, together with considerable local recreational fishery which might act as a slope-increasing factor, due to the elimination of organisms with greater biovolumes (i.e. fish). Another indicative of disturbance are the high slopes found (over -1.30 in most cases). These slopes indicate irregularities in the distribution of biomass among size classes. Indeed, the greatest biomass values were found in the class 0.031 – 0.063 mm3 (figure 8, whilst biomass values in classes from 1 to 64 mm3 were much lower, giving steeper slopes.

ACKNOWLEDGMENTS

The present work was supported by the Excellence Project P06-RNM-01637 of the Junta de Andalucía.

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THE EARTHSHINE TELESCOPE PROJECT

ABSTRACT

The Earthshine telescope project is a collaborative effort between Lund Observatory (LO) in Sweden and the Danish Meteorological Institute (DMI) with the purpose of constructing one or more robotic telescopes to record the albedo of the Earth over a long time. The objective is to measure long-term development of the global cloud cover and reflectivity for climate modeling. A 1% change in the Earth’s albedo results in an average temperature change of 0.5 K which calls for high precision in the albedo measurements. This poses strict demands on the telescope design, in particular with respect to suppression of straylight. The paper describes our proposed optical and mechanical design of the Earthshine telescope, and presents a preliminary straylight analysis of the design as well as first steps towards an ‘error budget’ for the system. Polarisation due to light-path folding could be an issue for the design being studied.

INTRODUCTION

Global warming will dramatically change our environment and affect us all. Climate models are essential tools in trying to understand the causes and mechanisms of global temperature changes. In Figure 1 the schematic radiation budget for Earth is shown. A very small change in the flux balance will have a large impact on the climate and temperature on the Earth. For this reason it is crucial to know the precise value and the trend of development of the albedo (reflectivity) of the Earth.

During the latest ten years Earth’s albedo has

been studied both from the Earth[1,2,3] and from satellites[4]. Obviously Earth-based measurements represent the cheaper alternative, but discrepancies exist between the results and the precision of both types of measurements can be, and are presently discussed.

The objective of the LO/DMI Earthshine project is to construct and test a robotic telescope capable of autonomous long time monitoring of the Earth’s albedo with a precision of on the order of 0.1%. If successful, it is planned to deploy more telescopes

(*) [email protected]; phone +46462227313; fax +46462224614(1) Lund Observatory, Box 43, S-22100 Lund, Sweden(2) Danish Meteorological Institute, Lyngbyvej 100, DK-2100 Copenhagen. Ø, Denmark(3) Departamento de Física Aplicada, Universidade de Vigo, E-36310 Vigo, Spain


Key words: Telescopes, Climate, Earthshine.

M. OWNER-PETERSEN(1,*), T. ANDERSEN(1), P. THEJLL(2), H. GLEISNER(2), A. ARDEBERG(1) & A. ULLA(3)

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120

M. OWNER-PETERSEN, T. ANDERSEN, P. THEJLL, H. GLEISNER, A. ARDEBERG & A. ULLA

to provide global coverage of the measurements. The observational principle is sketched in Figure 2.

Simultaneous or sequential intensity measurements are made on the dark and the bright sides of the Moon. The ratio of these measurements is proportional to the Earth’s albedo, and it is also independent of solar radiation intensity and atmospheric transmission. Since the goal is a precision of 0.1% and the ratio of the intensities at the bright and the dark sides of the Moon can be as big as 104, the relative straylight level at the dark side arising from the bright side is of particular concern especially for simultaneous measurements. Several designs to overcome both the problem of the large bright side versus dark side dynamics and the straylight requirements have been investigated, for an overview see[5]. In order to eliminate as many common error-sources as possible one would prefer simultaneous exposures of the dark and the bright side using the same optics. This requires a camera with a high full well capacity exposed to near saturation on the bright side. Even with the best cameras of today, the noise level on the dark side exposures will

be intolerable and an average over several hundreds of exposures of the dark side is required to reach the wanted precision. Realization of this scheme[5]

has also shown a strange glare pattern stretching out from the rim of the bright side, which could be caused either by atmospheric scattering or by straylight. The explanation is presently not clear. In order to eliminate bright side light diffracted from the entrance pupil,

The Earthshine Telescope Project M. Owner-Petersen*a, T. Andersena, P. Thejllb

, H. Gleisnerb, A. Ardeberga and A. Ullac

aLund Observatory, Box 43, S-22100 Lund, Sweden bDanish Meteorological Institute, Lyngbyvej 100, DK-2100 Copenhagen. Ø, Denmark cDepartamento de Física Aplicada, Universidade de Vigo, E-36310 Vigo, Spain

ABSTRACT

The Earthshine telescope project is a collaborative effort between Lund Observatory (LO) in Sweden and the Danish Meteorological Institute (DMI) with the purpose of constructing one or more robotic telescopes to record the albedo of the Earth over a long time. The objective is to measure long-term development of the global cloud cover and reflectivity for climate modeling. A 1% change in the Earth’s albedo results in an average temperature change of 0.5 K which calls for high precision in the albedo measurements. This poses strict demands on the telescope design, in particular with respect to suppression of straylight. The paper describes our proposed optical and mechanical design of the Earthshine telescope, and presents a preliminary straylight analysis of the design as well as first steps towards an ‘error budget’ for the system. Polarisation due to light-path folding could be an issue for the design being studied.

Keywords: Telescopes, Climate, Earthshine

1. INTRODUCTIONGlobal warming will dramatically change our environment and affect us all. Climate models are essential tools in trying to understand the causes and mechanisms of global temperature changes. In Figure 1 the schematic radiation budget for Earth is shown. A very small change in the flux balance will have a large impact on the climate and temperature on the Earth. For this reason it is crucial to know the precise value and the trend of development of the albedo (reflectivity) of the Earth.

Figure 1. Balance between the radiation and heat flux in W/m2, which enters and leaves the Earth (Trenberth, IPCC).

*[email protected]; phone +46462227313; fax +46462224614Figure 1:

Balance between the radiation and heat flux in W/m2, which enters and leaves the Earth (Trenberth, IPCC).

During the latest ten years Earth’s albedo has been studied both from the Earth[1,2,3] and from satellites[4]. Obviously Earth-based measurements represent the cheaper alternative, but discrepancies exist between the results and the precision of both types of measurements can be, and are presently discussed.

The objective of the LO/DMI Earthshine project is to construct and test a robotic telescope capable of autonomous long time monitoring of the Earth’s albedo with a precision of on the order of 0.1%. If successful, it is planned to deploy more telescopes to provide global coverage of the measurements. The observational principle is sketched in Figure 2.

Figure 2. Albedo measurements by simultaneous observation of the dark and the bright side of the Moon

Simultaneous or sequential intensity measurements are made on the dark and the bright sides of the Moon. The ratio of these measurements is proportional to the Earth’s albedo, and it is also independent of solar radiation intensity and atmospheric transmission. Since the goal is a precision of 0.1% and the ratio of the intensities at the bright and the dark sides of the Moon can be as big as 104, the relative straylight level at the dark side arising from the bright side is of particular concern especially for simultaneous measurements. Several designs to overcome both the problem of the large bright side versus dark side dynamics and the straylight requirements have been investigated, for an overview see[5]. In order to eliminate as many common error-sources as possible one would prefer simultaneous exposures of the dark and the bright side using the same optics. This requires a camera with a high full well capacity exposed to near saturation on the bright side. Even with the best cameras of today, the noise level on the dark side exposures will be intolerable and an average over several hundreds of exposures of the dark side is required to reach the wanted precision. Realization of this scheme[5] has also shown a strange glare pattern stretching out from the rim of the bright side, which could be caused either by atmospheric scattering or by straylight. The explanation is presently not clear. In order to eliminate bright side light diffracted from the entrance pupil, relay imaging optics with a Lyot stop in the pupil image is necessary[1,2,3]. This provides an intermediate focus, where a variable neutral density (ND) filter could be inserted in order to attenuate the bright side. It however results in a focal discrepancy between the dark and the bright side, and it also requires a rather complicated calibration procedure for the filter. The presently most successful scheme[3] relies on sequential exposures. When exposing the dark side, the bright side is completely blocked, and controlling the exposure times with a mechanical shutter ensures exposing to near saturation for both the dark and the bright side. This takes care of both contaminations with straylight from the bright side and of dark exposure noise. In order to control the bright side exposures with sufficient precision, the focal ratio of the telescope must be quite large resulting in dark side exposures of several minutes. Hence atmospheric conditions may change between dark and bright exposures, possibly leading to intolerable individual errors. Used in the foreseen operational mode, the LO/DMI design addresses the above-mentioned problems, and it also provides means for a mutual comparison of all of the methods.

Figure 2: Albedo measurements by simultaneous observation of the dark and the bright side of the Moon

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relay imaging optics with a Lyot stop in the pupil image is necessary[1,2,3]. This provides an intermediate focus, where a variable neutral density (ND) filter could be inserted in order to attenuate the bright side. It however results in a focal discrepancy between the dark and the bright side, and it also requires a rather complicated calibration procedure for the filter. The presently most successful scheme[3] relies on sequential exposures. When exposing the dark side, the bright side is completely blocked, and controlling the exposure times with a mechanical shutter ensures exposing to near saturation for both the dark and the bright side. This takes care of both contaminations with straylight from the bright side and of dark exposure noise. In order to control the bright side exposures with sufficient precision, the focal ratio of the telescope must be quite large resulting in dark side exposures of several minutes. Hence atmospheric conditions may change between dark and bright exposures, possibly leading to intolerable individual errors. Used in the foreseen operational mode, the LO/DMI design addresses the above-mentioned problems, and it also provides means for a mutual comparison of all of the methods.

THE LO/DMI EARTHSHINE TELESCOPE

The LO/DMI telescope is intended for fully automated operation. The proposed layout is shown in Figure 3. The optics and the camera is mounted in a sealed box, which can be rotated around the polar axis (in the plane of the optics) to provide tracking, and around a horizontal axis (perpendicular to the plane of the optics) to provide the correct declination. For adversary weather conditions the telescope will automatically be parked turning the box around the horizontal axis to a position where the two entrance apertures are closed by a fixed stop. The camera and thus its enclosure will have its temperature actively controlled and will exchange heat with the surroundings via the heat exchanger shown to the right in Figure 3.

As can be seen from Figure 3 the telescope has two arms. The upper dark arm is intended for observations of the Earthshine and is similar in design to the telescope first designed at the Big Bear Solar Observator[3] (BBSO) and now also used at e.g. Tenerife. Our design contains a removable occulter. The bright

2. THE LO/DMI EARTHSHINE TELESCOPE The LO/DMI telescope is intended for fully automated operation. The proposed layout is shown in Figure 3. The optics and the camera is mounted in a sealed box, which can be rotated around the polar axis (in the plane of the optics) to provide tracking, and around a horizontal axis (perpendicular to the plane of the optics) to provide the correct declination. For adversary weather conditions the telescope will automatically be parked turning the box around the horizontal axis to a position where the two entrance apertures are closed by a fixed stop. The camera and thus its enclosure will have its temperature actively controlled and will exchange heat with the surroundings via the heat exchanger shown to the right in Figure 3.

Figure 3. Layout of the LO/DMI Earthshine telescope showing both the dark (Earthshine) and bright (Monnshine) arm. The mechanical enclosure is also shown.

As can be seen from Figure 3 the telescope has two arms. The upper dark arm is intended for observations of the Earthshine and is similar in design to the telescope first designed at the Big Bear Solar Observator[3] (BBSO) and now also used at e.g. Tenerife. Our design contains a removable occulter. The bright arm is intended for observation of the Moonshine and contains a variable ND filter for attenuating the Moonshine to the same level as the Earthshine from the dark arm, so that the CCD can record simultaneous exposures. Not shown in the figure are a shutter and an IR/UV blocking filter to be located near the Lyot stop. The CCD has a high full-well capacity, and the dark arm can also be used for sequential exposures by moving the occulter in and out (the BBSO mode). The location of the ND filter means that it affects all field points in the same way. Relative transmission of the two arms as function of filter density can (and should regularly) be calibrated by observing the same standard stars either sequentially or simultaneously, but slightly displaced in the two arms. The pellicle beam-splitter provides 8% reflection and 92% transmission, but may also act as an analyzer of polarized light – an issue that will have to be dealt with by careful calibration. Since the dark side of the Moon determines the exposure time, the focal ratio of the telescope is two times smaller than the BBSO design allowing for four times shorter exposure times (for identical magnification and full-well CCD capacity). As can be seen the design allows for comparing the different schemes of observation described in the introduction. In order to provide adequate shutter control for co-added and sequential exposures, it may be necessary to stop down the aperture (including the Lyot stop) of the dark arm. The bright arm may be used without modifications for co-added exposures.

The optics consist of a 250 mm objective (250 mm f/5) followed by an afocal 1:2 relay optics consisting of a 50 mm and a 100 mm lens (50 mm f/4 and 100 mm f/8). All lenses are achromatic doublets. Both arms have a focal ratio of f/12.5. The CCD is a 512x512 array of 13x13 �m2 pixels (Andor iKon-M DU-937N-BV) providing a full field of view of 0.76o.

Figure 3: Layout of the LO/DMI Earthshine telescope showing both the dark (Earthshine) and bright (Monnshine) arm.The mechanical enclosure is also shown.

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arm is intended for observation of the Moonshine and contains a variable ND filter for attenuating the Moonshine to the same level as the Earthshine from the dark arm, so that the CCD can record simultaneous exposures. Not shown in the figure are a shutter and an IR/UV blocking filter to be located near the Lyot stop. The CCD has a high full-well capacity, and the dark arm can also be used for sequential exposures by moving the occulter in and out (the BBSO mode). The location of the ND filter means that it affects all field points in the same way. Relative transmission of the two arms as function of filter density can (and should regularly) be calibrated by observing the same standard stars either sequentially or simultaneously, but slightly displaced in the two arms. The pellicle beam-splitter provides 8% reflection and 92% transmission, but may also act as an analyzer of polarized light – an issue that will have to be dealt with by careful calibration. Since the dark side of the Moon determines the exposure time, the focal ratio of the telescope is two times smaller than the BBSO design allowing for four times shorter exposure times (for identical magnification

and full-well CCD capacity). As can be seen the design allows for comparing the different schemes of observation described in the introduction. In order to provide adequate shutter control for co-added and sequential exposures, it may be necessary to stop down the aperture (including the Lyot stop) of the dark arm. The bright arm may be used without modifications for co-added exposures.

The optics consist of a 250 mm objective (250 mm f/5) followed by an afocal 1:2 relay optics consisting of a 50 mm and a 100 mm lens (50 mm f/4 and 100 mm f/8). All lenses are achromatic doublets. Both arms have a focal ratio of f/12.5. The CCD is a 512x512 array of 13x13 µm2 pixels (Andor iKon-M DU-937N-BV) providing a full field of view of 0.76º. The performance has been investigated using ZEMAX, and although not diffraction limited it shows a reasonable match to the pixel size. This can be seen in Figure 4 showing the encircled energy fraction as function of radius for the three field angles 0, 0.25 and 0.4 degrees

The performance has been investigated using ZEMAX, and although not diffraction limited it shows a reasonable match to the pixel size. This can be seen in Figure 4 showing the encircled energy fraction as function of radius for the three field angles 0, 0.25 and 0.4 degrees

Figure 4. Encircled energy for the LO/DMI Earthshine telescope. Diffraction effects are included.

3. STRAYLIGHT INVESTIGATIONS OF THE LO/DMI TELESCOPE In order to evaluate whether the telescope can meet the demands for a ~0.1% precision of the albedo measurement, it has been preliminary investigated for straylight performance. The contributions to straylight come from:

(i) Ghosts. That is light being reflected from surfaces supposed to be transmitting and finally ending up on the CCD.

(ii) Scattered light. That is light being scattered one or more times from supposedly absorptive surfaces, or from dust on the optical surfaces as e.g. the first surface of the objective lens. Scattered light in the dark arm may originate from both the wanted object (The Earthshine) or from unwanted objects (The Moonshine, the sky or even the Sun).

Figure 5 shows the configuration used for straylight analysis of the dark arm. The baffle ensures that light sources more than 30o away from the axial source will hit the baffle before being scattered into the optics. The tube, the lens mounts and the stops (apart from the aperture sizes) are here considered preliminary. In the following they are modeled as 100% absorptive, and so is the baffle. A more detailed analysis of straylight arising from scattering by these surfaces must await a more detailed knowledge of the mechanical design and a more detailed knowledge of the so-called bi-directional

Figure 4: Encircled energy for the LO/DMI Earthshine telescope. Diffraction effects are included.

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STRAYLIGHT INVESTIGATIONS OF THE LO/DMI TELESCOPE

In order to evaluate whether the telescope can meet the demands for a ~0.1% precision of the albedo measurement, it has been preliminary investigated for straylight performance. The contributions to straylight come from:

(i) Ghosts. That is light being reflected from surfaces supposed to be transmitting and finally ending up on the CCD.

(ii) Scattered light. That is light being scattered one or more times from supposedly absorptive surfaces, or from dust on the optical surfaces as e.g. the first surface of the objective lens. Scattered light in the dark arm may originate from both the wanted object (The Earthshine) or from unwanted objects (The Moonshine, the sky or even the Sun).

Figure 5 shows the configuration used for straylight analysis of the dark arm. The baffle ensures that light sources more than 30º away from the axial source will hit the baffle before being scattered into the optics. The tube, the lens mounts and the stops (apart from the aperture sizes) are here considered preliminary. In the following they are modeled as 100% absorptive, and so is the baffle. A more detailed analysis of straylight arising from scattering by these surfaces must await a more detailed knowledge of the mechanical design and a more detailed knowledge of the so-called bi-directional reflection distribution function (BRDF) to be associated with them. Ideally they should be 100% absorptive. The CCD is considered to be 5% mirror reflective in accordance with a quantum efficiency of 95% (this may be too optimistic!). The straylight analysis presented in the following only comprises a ghost analysis (including coating performance) from objects within the field and a simple analysis of scattering from the front face of the objective lens assuming Lambertian scattering.

reflection distribution function (BRDF) to be associated with them. Ideally they should be 100% absorptive. The CCD is considered to be 5% mirror reflective in accordance with a quantum efficiency of 95% (this may be too optimistic!). The straylight analysis presented in the following only comprises a ghost analysis (including coating performance) from objects within the field and a simple analysis of scattering from the front face of the objective lens assuming Lambertian scattering.

Figure 5. Setup used for straylight analysis showing both the direct rays to the wanted image point and rays associated with thecorresponding ghosts. The latter ones results from a non-sequential raytrace.

3.1 Ghost performance

‘Ghosts’ arise from light being reflected from surfaces where it should supposedly only be transmitted. According to the Fresnel formulas there will in general be some light reflected at a surface separating two media with different refractive indices, but the effect can be reduced by coating the surface with some kind of anti-reflex coating. In order for the light to end up at the CCD, there must be an even number of ghost reflections and the ghosts involving only two reflections are of course the most powerful ones. In a design including three doublets and a partly reflective CCD there will be 45 such double-bounce ghosts. A quantitative evaluation of the power associated with the ghosts requires detailed knowledge of the shape of the doublets (which we have here) and knowledge of the lens coatings, of which there exist

Aperture Stop Field Stop Lyot Stop CCD

Baffle Tube Lens Mounts Backplate

Figure 5: Setup used for straylight analysis showing both the direct rays to the wanted image point and rays associated with the corresponding ghosts. The latter ones results from a non-sequential raytrace.

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Ghost performance

‘Ghosts’ arise from light being reflected from surfaces where it should supposedly only be transmitted. According to the Fresnel formulas there will in general be some light reflected at a surface separating two media with different refractive indices, but the effect can be reduced by coating the surface with some kind of anti-reflex coating. In order for the light to end up at the CCD, there must be an even number of ghost reflections and the ghosts involving only two reflections are of course the most powerful ones. In a design including three doublets and a partly reflective CCD there will be 45 such double-bounce ghosts. A quantitative evaluation of the power associated with the ghosts requires detailed knowledge of the shape of the doublets (which we have here) and knowledge of the lens coatings, of which there exist several standard types (matched to the wanted wavelength range), which can be ordered from the lens-supplier. For our purpose (imaging in the visual range) the choice is between standard AR (anti-reflex) coating consisting of a quarter-wave layer of MgF2 and WAR (wide band anti-reflex) coating consisting of a quarter-wave layer of MgF2 and a half-wave layer of La2F3. Instead of analyzing the performance of the ghosts one by one it is more efficient to perform a non-sequential raytrace, which will also include the contributions from higher order ghosts. An example of such a raytrace launching ten non-sequential rays is shown in Figure 5. In the analysis carried out here 105 rays carrying in total 1 W of power were launched axially into the aperture stop. Most of the power was carried to the central four pixels and the rest was evenly spread over the CCD. In the case of coating with WAR, the central intensity (in the four axial pixels) was

CI0 = 9.69x104 W/cm2

and the total ghost power collected at the CCD was

TGP0 =4.28x10-5 W

collected over an area of

w2 = 0.66562 cm2

This results in a ghost-associated signal to noise ratio of

SNRg = 1.00x109

Coating the lenses with AR leads to a SNRg being 2.5 times smaller. It is seen that ghost contamination from dark side pixels will be no problem, but contamination from bright side pixels (in case of no occulter) being up to 104 times brighter than the dark side pixels may lead to problems. Aiming at a precision of ~0.1%, the allowable number of bright pixels will be 4xSNRg/107 = 400. When the lunar phase changes, the number of brightly illuminated pixels will also change and so will their contribution to the background level in the dark side. If there are more than 400 bright pixels, these variations will surpass the 0.1% precision level. Closer investigations revealed that the main part of the ghost level was due to double-bounces in the relay-optics. The above results indicate that bright side pixels must be blocked in the front focus of the dark arm or attenuated (in the bright arm) in order to get reliable dark side exposures. They also indicate that choosing the best available coating is important.

Performance for additional scatter at the objective

The effect of scattering from the front face of the objective is next considered. In order to evaluate the contribution from this at the CCD, one must know the scattering model, which, for simplicity has been assumed to be Lambertian (this might be too optimistic, since it scatters quite few rays in the near axial direction). Establishing a model for the total signal to noise as a function of the scatter fraction x (between 0 and 1) requires knowledge of four parameters: (i) The central intensity level CI0 (W/cm2) in case of no scattering, (ii) The total power TSC1 (W) collected by the CCD in case of 100% scattering. (iii)

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The width w of the detector. (iv) The total number Nm of pixels spanned by the Moon on the detector. The values of the four parameters are:

CI0 = 9.69x104 W/cm2

TSC1 = 2.69x10-5 W

w2 = 0.66562 cm2

Nm = 8.9x104

In order to obtain reasonable statistics for TSC1 it was necessary to trace 107 rays carrying in total 1 W. Letting reff denote the intensity ratio between bright and dark pixels, where reff is a function of the lunar phase or the number Nm of bright pixels, the signal to noise ratio SNRL in the LO/DMI telescope can be estimated as

Related to the lunar phase α the number of bright pixels can be expressed by

Nb = Nm (1+cos(α))/2

Here α = 0º corresponds to full Moon and α = 180º to new Moon. Knowing the lunar phase function Φ(α) the intensity ratio can roughly (assuming constant dark side intensity) be estimated by:

The lunar phase function can to a reasonable degree of accuracy [6] be approximated by:

Figure 6 shows reff as function of α and Figure 7 shows SNRL as function of the scatter fraction x with α as parameter.

From Figure 7 it is seen that tolerable scattering levels corresponding to a 0.1 % precision level (log(SNR)=3) will only be a few percent when observing at more than half Moon, whereas it can be more than 10 % (scattering fraction > 0.1) when observing at less than half Moon. It should be noticed that increasing the scattering level x would increase the exposure time needed to reach saturation of the CCD.

The signal to noise ratios SNRS and SNRC respectively associated with operating in sequential exposure (BBSO) mode and co-adding image mode can be calculated from the following expressions:

Figure 8 and 9 show SNRS and SNRC as function of the scatter-fraction x with the phase α as parameter.

Comparing Figure 7 and 8 it is seen that the

straylight performances are not very different for the double arm and the single arm sequential mode.

Related to the lunar phase � the number of bright pixels can be expressed by

Nb = Nm (1+cos(�))/2

Here � = 0o corresponds to full Moon and � = 180o to new Moon. Knowing the lunar phase function �(�) the intensity ratio can roughly (assuming constant dark side intensity) be estimated by:

)(NN

)(10)(rb

m4eff �

��

The lunar phase function can to a reasonable degree of accuracy [6] be approximated by: 49.3

)( ��

��

��

��

Figure 6 shows reff as function of � and Figure 7 shows SNRL as function of the scatter fraction x with � as parameter.

Figure 6. Intensity ratio reff as function of the lunar phase in radians

From Figure 7 it is seen that tolerable scattering levels corresponding to a 0.1 % precision level (log(SNR)=3) will only be a few percent when observing at more than half Moon, whereas it can be more than 10 % (scattering fraction > 0.1) when observing at less than half Moon. It should be noticed that increasing the scattering level x would increase the exposure time needed to reach saturation of the CCD.

The signal to noise ratios SNRS and SNRC respectively associated with operating in sequential exposure (BBSO) mode and co-adding image mode can be calculated from the following expressions:

bmeffb10

20

C

1bmeffb0bm

20

S

NNrN1

xTSC)x1(TGPw)x1(CI4

SNR

xTSC)NNrN()x1(TGP)NN(w)x1(CI4

SNR

��

��

�

��

�

Figure 8 and 9 show SNRS and SNRC as function of the scatter-fraction x with the phase � as parameter.

Figure 6:Intensity ratio reff as function of the lunar phase in radians

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Figure 7. Logarithmic plot of the signal to noise ratio of the LO/DMI telescope. SNRL is shown as a function of the scatter-fraction x with the phase � of the Moon as parameter. Upper curve: � = 180o (new Moon). Second to top curve: � = 135o. Mid curve: � = 90o

(half Moon). Second to bottom curve: � = 45o and bottom curve: � = 0o (full Moon). Lowest acceptable Signal-to-Noise ratio is log(SNR)=3. Operation mode: Standard (double-arm) addition.

Figure 8. Logarithmic plot of the signal to noise ratio of the LO/DMI telescope. SNRS is shown as a function of the scatter-fraction x with the phase of the Moon as parameter. Upper curve: � = 180o (new Moon). Second to top curve: � = 135o. Mid curve: � = 90o (half Moon). Second to bottom curve: � = 45o and bottom curve: � = 0o (full Moon). Lowest acceptable Signal-to-Noise ratio is log(SNR)=3. Operation mode: Single arm sequential exposures (BBSO-mode).

Figure 7: Logarithmic plot of the signal to noise ratio of the LO/DMI telescope. SNRL is shown as a function of the scatter-fraction x

with the phase α of the Moon as parameter. Upper curve: α = 180º (new Moon). Second to top curve: α = 135º. Mid curve: α = 90º(half Moon). Second to bottom curve: α = 45º and bottom curve: α = 0º (full Moon). Lowest acceptable Signal-to-Noise ratio is log(SNR)=3.

Operation mode: Standard (double-arm) addition.Figure 7. Logarithmic plot of the signal to noise ratio of the LO/DMI telescope. SNRL is shown as a function of the scatter-fraction x with the phase � of the Moon as parameter. Upper curve: � = 180o (new Moon). Second to top curve: � = 135o. Mid curve: � = 90o

(half Moon). Second to bottom curve: � = 45o and bottom curve: � = 0o (full Moon). Lowest acceptable Signal-to-Noise ratio is log(SNR)=3. Operation mode: Standard (double-arm) addition.

Figure 8. Logarithmic plot of the signal to noise ratio of the LO/DMI telescope. SNRS is shown as a function of the scatter-fraction x with the phase of the Moon as parameter. Upper curve: � = 180o (new Moon). Second to top curve: � = 135o. Mid curve: � = 90o (half Moon). Second to bottom curve: � = 45o and bottom curve: � = 0o (full Moon). Lowest acceptable Signal-to-Noise ratio is log(SNR)=3. Operation mode: Single arm sequential exposures (BBSO-mode).

Figure 8: Logarithmic plot of the signal to noise ratio of the LO/DMI telescope. SNRS is shown as a function of the scatter-fraction x

with the phase of the Moon as parameter. Upper curve: α = 180º (new Moon). Second to top curve: α = 135º. Mid curve: α = 90º (half Moon). Second to bottom curve: α = 45º and bottom curve: α = 0º (full Moon). Lowest acceptable Signal-to-Noise ratio is log(SNR)=3.

Operation mode: Single arm sequential exposures (BBSO-mode).

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Looking at Figure 9 it is however seen that single arm operation with co-addition of images will only meet the 0.1% specs close to new Moon, where the Sun and the bright sky may be expected to give other problems. The reason for the deteriorated performance is the straylight due to ghosts created by the bright side of the Moon.

TOWARDS AN ERROR BUDGET

The Science goals set the requirements for the design of this telescope. We hope to be able to measure terrestrial albedo with a precission (i.e. the scatter or random error) of half a percent, since this will allow modelling of the large scale albedo variations that occur on timescales of days and weeks due to weather patterns moving across the surface of the Earth. On decadal time scales we want to have accuracies (i.e. bias) that is as low as one or two tenths of a percent. These are somewhat extreme requirements – especially that for the bias – but they are softened by the realization that in practise biases can be

manageable, as long as they are time-invariable. If we can have ‘constant biases’ we will be happy if they are ‘small’ and do not change by more than one or two tenths of a percent on decadal time-scales. If these conditions can be met we can do climate-change research with the data and be sure that trends have not been introduced by the instrumentation. A ‘constant bias’ is all right if you have only one instrument or a set of instruments that are the same, but if we wish to use data from other instruments or contribute to a joint data-bank of earthshine measurements, then the issue of knowing just how large the bias is and how it evolves over time becomes central. This can in principle be handled by performing inter-calibrations between instruments – i.e. setting up calibration session where transportable instruments are brought to a joint site for a campaign of observations over a period of days or weeks.

We have considered the various sources of scatter and bias in the current design and can identify the issues of scattered-light removal and flat-fielding as

Figure 9. Logarithmic plot of the signal to noise ratio of the LO/DMI telescope. SNRC is shown as a function of the scatter-fraction x with the phase of the Moon as parameter. Upper curve: � = 180o (new Moon). Second to top curve: � = 135o. Mid curve: � = 90o (half Moon). Second to bottom curve: � = 45o and bottom curve: � = 0o (full Moon). Lowest acceptable Signal-to-Noise ratio is log(SNR)=3. Operation mode: Single arm without occulter and co-addition of images.

Comparing Figure 7 and 8 it is seen that the straylight performances are not very different for the double arm and the single arm sequential mode. Looking at Figure 9 it is however seen that single arm operation with co-addition of images will only meet the 0.1% specs close to new Moon, where the Sun and the bright sky may be expected to give other problems. The reason for the deteriorated performance is the straylight due to ghosts created by the bright side of the Moon.

4. TOWARDS AN ERROR BUDGET The Science goals set the requirements for the design of this telescope. We hope to be able to measure terrestrial albedo with a precission (i.e. the scatter or random error) of half a percent, since this will allow modelling of the large scale albedo variations that occur on timescales of days and weeks due to weather patterns moving across the surface of the Earth. On decadal time scales we want to have accuracies (i.e. bias) that is as low as one or two tenths of a percent. These are somewhat extreme requirements – especially that for the bias – but they are softened by the realization that in practise biases can be manageable, as long as they are time-invariable. If we can have ‘constant biases’ we will be happy if they are ‘small’ and do not change by more than one or two tenths of a percent on decadal time-scales. If these conditions can be met we can do climate-change research with the data and be sure that trends have not been introduced by the instrumentation. A ‘constant bias’ is all right if you have only one instrument or a set of instruments that are the same, but if we wish to use data from other instruments or contribute to a joint data-bank of earthshine measurements, then the issue of knowing just how large the bias is and how it evolves over time becomes central. This can in principle be handled by performing inter-calibrations between instruments – i.e. setting up calibration session where transportable instruments are brought to a joint site for a campaign of observations over a period of days or weeks.

We have considered the various sources of scatter and bias in the current design and can identify the issues of scattered-light removal and flat-fielding as the dominant terms. These can give rise to biases. The issue of correcting for differential extinction across the image plane is a source of random error but can be avoided if observations are kept to airmasses below 2, which is good photometric practise anyway. Observing schedules will be affected by this

Figure 9: Logarithmic plot of the signal to noise ratio of the LO/DMI telescope. SNRC is shown as a function of the scatter-fraction x

with the phase of the Moon as parameter. Upper curve: α = 180º (new Moon). Second to top curve: α = 135º. Mid curve: α = 90º (half Moon). Second to bottom curve: α = 45º and bottom curve: α = 0º (full Moon). Lowest acceptable Signal-to-Noise ratio is

log(SNR)=3. Operation mode: Single arm without occulter and co-addition of images.

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the dominant terms. These can give rise to biases. The issue of correcting for differential extinction across the image plane is a source of random error but can be avoided if observations are kept to airmasses below 2, which is good photometric practise anyway. Observing schedules will be affected by this requirement, however. High-quality falt-fielding methods will have to be used – the possible advantages of the Kuhn, Lin, & Loranz[7] method, and their like, are under investigated.

Since the present design relies on a folded light-path the effects of polarization need to be considered. Moon-light and Earthshine is polarized (up to about 10%, depending on lunar phase[8]. The mirrors intended are typically metal front-surface mirrors and may contribute or detract polarisation to the light. The impact of this on the science goals must be investigated.

CONCLUSIONS

The design of a telescope intended for long term automatic monitoring of the albedo of the Earth has been presented. A preliminary analysis of straylight performance of the design has been carried out. For the simple case of Lambertian scattering at the front surface of the objective it seems to perform according to specifications, when the lenses are optimally coated and the bright side of the Moon is occulted in the front focus of the dark arm and attenuated in the bright arm. Simultaneous exposures of the dark and the bright side of the Moon are expected to give problems. Scattering at the front surface of the objective must be kept below a few percent, so the front surface of the dark arm objective may need regular cleaning depending on conditions at the chosen site. The telescope is capable of operating in all presently implemented modes for existing Earthshine telescopes, and hence will be able to perform a comparison of these modes. Further work remains investigating straylight performance, in particular to consider more realistic scatter models for dust at the front surface, and to investigate the contribution to

the straylight from the sky background within the 60º field allowed by the baffle. The advantage of putting vanes on the front baffle should also be investigated, as should the effects of polarization due to the folding mirrors.

ACKNOWLEDGEMENTS

The authors would like to thank two anonymous referee for they useful comments.

The authors thank the Swedish foundation VINNOVA for providing funding for this investigation plus for erection of a single prototype at a suitable location, probably in Australia. Support from the British Embassies in Denmark, Austria and Switzerland for an international workshop on Earthshine, held in Lund in January 2008, is also gratefully acknowledged. A review performed by Jacques Beckers is warmly appreciated.

REFERENCES

Pallé, E., Goode, P.R., Montañés-Rodriguez P. and Koonin, S.E., “Earthshine and Earth’s reflectivity,” Bulletin of the American Astronomical Scociety 32, p833 (2000).

Pallé, E., Goode, P.R., Montañés-Rodriguez, P. and Koonin, S.E., “Changes in Earth’s reflectance over the past two decades,” Science 304, 1299-1301 (2004)

Pallé, E., Goode, P.R., Montañés-Rodriguez, P. and Koonin, S.E., “Can Earth’s albedo and surface temperatures increase together?,” EOS, Transactions American Geophysical Union 87, p37 (2006).

Sun, W., et al., “Comparison of MISR and CERES top-of-atmosphere albedo”, Geophysical Research Letters, Volume 33, Issue 23, CiteID L23810 (2006); and e.g. CERES http://science.larc.nasa.gov/ceres/index.html

Thejll, P.,Flynn, C., Gleisner, H. and Mattingly, A., “Earthshine: Not just for romantics,” A&G 49, 3.15-3.20 (2008)

Allen, C.W.,[Astrophysical Quantities], The Athlone Press, London & Atlantic Highlands, Ed. 3, p 143 (1972)

Kuhn, J. R., Lin, H., & Loranz, D. PASP, 103, 1097 (1991) Können, G. P. “Polarized light in nature”, Cambridge

University Press, 1985.


129

GENE FLOW, MULTILOCUS ASSIGNMENT AND GENETIC STRUCTURING OF THE EUROPEAN HAKE

(MERLUCCIUS MERLUCCIUS)

ABSTRACT

Incorporating population genetic data into assessment processes would prove useful for the management of hake fisheries. We have analysed the molecular variation of five polymorphic microsatellites and a 465 bp fragment from the cytochrome b gene on 27 hake populations to determine the genetic status of this species across European fisheries. While weak genetic differences (FCT = 0.0092, P < 0.01) exist between the seven major oceanographic regions considered (North Sea, Celtic Sea, Cantabrian Sea, Iberian Atlantic, Iberian Mediterranean, Tyrrhenian Sea and Canarian Sea), the deepest partition resides between Atlantic and Mediterranean populations. However, the probability of the 712 multilocus genotypes scored to be assigned to Atlantic or to Mediterranean basins is fairly 0.5, indicating that these two geographical stocks cannot be reliably identified from each other neither for fishery forensics nor for commercial traceability.

INTRODUCTION

The European hake, Merluccius merluccius, is a species of great ecological and commercial value in Western Europe (Pitcher and Alheit, 1995). The European Union has adopted compulsory fishing regulations to avoid a severe decay of hake fisheries due to overexploitation. However, such management measures should also consider the actual genetic scenario of this species in EU fisheries. Previous studies using allozymes (e.g., Roldán et al., 1998; and microsatellites (e.g., Lundy et al., 1999) have reported the existence of a genetic split between Atlantic and Mediterranean populations of hake and a putative complex structure along the European Atlantic coast. In this study we have combined the variation of polymorphic microsatellites and the molecular variation of the cytochrome b gene to better understand the genetic scenario of the European hake. Supported by the large sampling effort developed, we aimed to clarify whether the differentiation signal between Atlantic and Mediterranean populations serves at reliably distinguishing them from each other or if it consists on a minor regional divergence between populations.

ECIMAT - Faculty of Marine Sciences, University of Vigo, 36310 Vigo, Spain,[email protected]

Key words: European hake, Merluccius merluccius, gene flow, multilocus asignment

A. PITA, P. PRESA & M. PEREZ

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Sampling

About 5,610 individuals of European hake were sampled in year 2000. The fisheries sampled ranged from the Tyrrhenian Sea to the Alboran Sea in the Mediterranean, from the Gulf of Cadiz to the Biscay Bay in Atlantic Iberian coasts, extending south to the Canarian Sea, and from Biscay Bay to the Celtic Sea extending to the North Sea. Genomic DNA from a sample set of 27 populations scattered along the fisheries sampled, was extracted using a combination of the salting-out method (Miller et al., 1988) and the standard phenol:chloroform method (Sambrook et al., 1998).

Microsatellite analyses

The five microsatellite markers used were previously described in this species, namely Mmer-hk3b, Mmer-hk9b, Mmer-hk20b, Mmer-hk29b, Mmer-hk34b (Morán et al., 1999). The variability of microsatellites was scored by genotyping all individuals (712) in an automatic fragment analyser ALFexpress II (GE Healthcare). Alleles were sized using molecular ladders (80-114-180-230-402 bp) and putative scoring errors were checked with MICRO-CHECKER 2.2.3 (van Oosterhout et al., 2004). The statistical rho and the estimated number of migrants per generation between regions were calculated with RST-CALC (Goodman, 1997). Analysis of Molecular Variance (Schneider et al., 2000) as implemented in

Figure 1: Correspondence between European hake cytochrome b haplotypes (Symbols) and their oceanographic sampling locations

distributed from the North Sea to the Tyrrhenian Sea.

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GENE FLOW, MULTILOCUS ASSIGNMENT AND GENETIC STRUCTURING OF THE EUROPEAN HAKE (MERLUCCIUS MERLUCCIUS)

ARLEQUIN 3.11 (Excoffier et al., 2005) was used to test the global spatial genetic structuring of hake populations. The probability of assignment of a given genotype to the Atlantic or to the Mediterranean basins was determined with the method of Maximum Likelihood (100,000 replicates with a burning threshold of 10,000) using STRUCTURE 2.2 (Pritchard et al., 2000).

Cytochrome b analyses

PCR amplifications were performed as described by Pérez and Presa (2008). The hypothesis of random distribution of individuals among populations was assessed with the global exact test of differentiation enforcing 100,000 Markov chains iterations. The distribution of the molecular variance (AMOVA) was explored with ARLEQUIN 3.11 (Excoffier et al., 2005), and the significance of the fixation indices was obtained from the null distribution of these statistics generated with a non-parametric method (10,000 permutations) by exchanging haplotypes, individuals or populations between the corresponding hierarchical levels enforced.

RESULTS AND DISCUSSION

Microsatellite variation

Differentiation coefficient rho (±SD) between pools of Atlantic and Mediterranean samples was highly significant (rho = 0.0386 ± 0.0728, P <0.001),

and larger than among Atlantic samples (0.028 ± 0.034) or among Mediterranean samples (0.019 ± 0.017). Estimated gene flow (Nm) between basins was 6.2 migrants per generation. Also the AMOVA performed by grouping all samples according to their Atlantic or Mediterranean origin, showed that 98.61% of the variation was due within populations, 0.48% within basins, and a significant 1.36% between basins (FCT = 0.0136, P < 0.01) (Table 1). These results are in agreement with previous studies reporting a reduced gene flow between basins, probably imposed by Gibraltar Strait and/or the Almería-Oran oceanographic front (Tintoré et al., 1991).

Such reduction to gene flow has been reported not only for hake populations using allozymes (Roldán et al., 1998) but also in many other species, i.e. Mytilus galloprovincialis (e.g., Diz and Presa, 2008). However, the probabilities of assignment of any Atlantic multilocus genotype, either to the Atlantic or to the Mediterranean were 0.509 and 0.491, respectively. Likewise, the probabilities of assignment of any Mediterranean multilocus genotype to the Atlantic or to the Mediterranean were 0.475 and 0.525, respectively.

Therefore, although the above estimations of differentiation between Atlantic and Mediterranean populations suggest some degree of isolation between them, the likelihood allocation of genotypes to basins indicates that the genetic distinction of populations from both basins is practically unaffordable.

2

Microsatellite analyses The five microsatellite markers used were previously described in this species,

namely Mmer-hk3b, Mmer-hk9b, Mmer-hk20b, Mmer-hk29b, Mmer-hk34b (Morán et al., 1999). The variability of microsatellites was scored by genotyping all individuals (712) in an automatic fragment analyser ALFexpress II (GE Healthcare). Alleles were sized using molecular ladders (80-114-180-230-402 bp) and putative scoring errors were checked with MICRO-CHECKER 2.2.3 (van Oosterhout et al., 2004). The statistical rho and the estimated number of migrants per generation between regions were calculated with RST-CALC (Goodman, 1997). Analysis of Molecular Variance (Schneider et al., 2003) as implemented in ARLEQUIN 3.11 (Excoffier et al., 2005)was used to test the global spatial genetic structuring of hake populations. The probability of assignment of a given genotype to the Atlantic or to the Mediterranean basins was determined with the method of Maximum Likelihood (100,000 replicates with a burning threshold of 10,000) using STRUCTURE 2.2 (Pritchard et al., 2000).

Cytochrome b analyses PCR amplifications were performed as described by Pérez and Presa (2008). The

hypothesis of random distribution of individuals among populations was assessed with the global exact test of differentiation enforcing 100,000 Markov chains iterations. The distribution of the molecular variance (AMOVA) was explored with ARLEQUIN 3.11 (Excoffier et al., 2005), and the significance of the fixation indices was obtained from the null distribution of these statistics generated with a non-parametric method (10,000 permutations) by exchanging haplotypes, individuals or populations between the corresponding hierarchical levels enforced.

3. RESULTS AND DISCUSSION

Microsatellite variation Differentiation coefficient rho (±SD) between pools of Atlantic and Mediterranean

samples was highly significant (rho = 0.0386 ± 0.0728, P <0.001), and larger than among Atlantic samples (0.028 ± 0.034) or among Mediterranean samples (0.019 ± 0.017). Estimated gene flow (Nm) between basins was 6.2 migrants per generation. Also the AMOVA performed grouping all samples according to their Atlantic or Mediterranean origin, showed that 98.61% of the variation was within populations, 0.48% within basins, and a significant 1.36% between basins (FCT = 0.0136, P < 0.01) (Table 1). These results are in agreement with previous studies reporting a reduced gene flow between basins, probably imposed by Gibraltar Strait and/or the Almería-Oran oceanographic front (Tintoré et al., 1991).

Table 1: AMOVA on the hierarchical partition between Atlantic (20 samples) and Mediterranean (7 samples) populations of hake. Source of variation D. f. Variance

components %variation

Fixation index

Among groups 1 0.02486 1.36 0.01363* Among populations within groups 25

0.00879 0.48 0.00488ns

Within populations 1469 1.79031 98.61 0.01845*

Total 1495 1.82396

Table 1: AMOVA on the hierarchical partition between Atlantic (20 samples) and Mediterranean (7 samples) populations of hake using microsatellites.

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Cytochrome b variation

The AMOVA performed on cytochrome b haplotypes within samples explained 99.16% of the molecular variation. Therefore, a non-significant variation of 0.14% was observed between basins, in agreement with a previous study performed with this mitochondrial marker on seven samples scattered along EU fisheries (Lundy et al., 1999). The distribution analysis of cytochrome b haplotypes (Figure 2) showed that some of them (Mmcytb.4,6,7,8,11) are specific of the Atlantic, and some other of the Mediterranean (Mmcytb.5,9,10), indicating a restricted gene flow between basins. However, haplotypes Mmcytb.2,3 were patently present from the North Sea to the Mediterranean Sea at at low frequency.

Both results, the existence of basin-specific haplotypes and across-basins low frequency haplotypes indicate a restricted but ongoing gene flow between basins. This pattern of diversity corresponds to a model expansive casual, i.e. the dispersion pattern of this species would depend on random oceanic fluctuations affecting passive dispersal of larvae and recruits (e.g., Sánchez and Gil, 2000) and/or active adult migration between basinsthe dispersion pattern of this species would depend on random oceanic fluctuations affecting passive dispersal of larvae and recruits (e.g., Sánchez and Gil, 2000) and/or active adult migration between basins.

ACKNOWLEDGEMENTS

This research was supported with grants from the Spanish Ministerio de Ciencia y Tecnología to PP (INIA RZ00/020) and MP (MIT99/236122076). The authors are indebted to all fishing organizations that assisted in sampling. Particularly we acknowledge the sampling effort developed by J. Ellis, L. Sampedro, F. Sánchez, F. Velasco, B. Patiño, M. Sainza and F. Badalamenti. The crews of the oceanographic vessels Vizconde de Eza and Cornide de Saavedra (IEO), as well as other European Oceanographic Institutes (CNR-IRMA from Italy and CEFAS from United Kingdom) have also cooperated actively in sampling.

REFERENCES

Diz AP and Presa P (2008). Regional patterns of microsatellite variation in Mytilus galloprovincialis from the Iberian Peninsula, Marine Biology, 154: 277–286.

Excoffier L, Laval G and Schneider S (2005). Arlequin ver. 3.0: An integrated software package for population genetics data analysis, Evolutionary Bioinformatics Online, 1: 47-50.

Goodman SJ (1997). Rst Calc: a collection of computer programs for calculating estimates of genetic differentiation from microsatellite data and a determining their significance, Molecular Ecology, 6: 881-885.

Lundy CJ, Morán P, Rico C, Milner RS and Hewitt GM (1999). Macrogeographical population differentiation in oceanic environments: a case study of European hake (Merluccius merluccius), a commercially important fish, Molecular Ecology, 8: 1889-1898.

Miller SA, Dykes DD and Polesky HF (1988). A simple salting out procedure for extracting DNA from human nucleated cells, Nucleic Acids Research, 16: 1215.

Morán P, Lundy C, Rico C and Hewitt GM (1999). Isolation and characterization of microsatellite loci in European hake, Merluccius merluccius (Merlucidae, Teleostei), Molecular Ecology, 8: 1357-1358.

Pérez M and Presa P (2008). Validation of tRNA-Glu-cytochrome b key for the molecular identification of twelve hake species (Merluccius spp.) and Atlantic cod (Gadus morhua) using PCR-RFLPs, FINS and BLAST. Journal of Agricultural and Food Chemistry, 56 (22): 10865-10871.

Pitcher T and Alheit J (1995) What makes a hake? A review of the critical biological features that sustain global hake fisheries. In: J Alheit and T Pitcher, eds., Hake: biology, fisheries and markets. Chapman & Hall, London, 1-14.

Pritchard JK, Stephens M and Donnelly P (2000). Inference of population structure using multilocus genotype data, Genetics, 155: 945-959.

Roldán MI, García JL, Utter FM and Pla C (1998). Population genetic structure of European hake, Merluccius merluccius, Heredity, 81: 327-334.

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Sambrook J, Fritsch EF and Maniatis T (1998) Commonly used techniques in molecular cloning. In: N Ford, C Nolan, M Ferguson eds., Molecular Cloning: A Laboratory Manual, 2nd ed., Colds Spring Harbour Laboratory Press, New York, E3-E4.

Sánchez F and Gil J (2000). Hydrographic mesoscale structures and poleward current as a determinant of hake (Merluccius merluccius) recruitment in Southern Bay of Biscay, ICES Journal of Marine Science, 57: 152-170.

Schneider S, Roessli D and Excoffier L (2000). Arlequin: A software for population genetics data analysis Vs 2.000, Genetics and Biometry Lab, Dept. of Anthropology, University of Geneva.

Tintoré J, Gomis D, Alonso S and Parrilla S (1991). Mesoscale dynamics and vertical motion in the Alboran Sea, Journal of Physical Oceanography, 21: 811-823.

Van Oosterhout C, Hutchinson WF, Wills DPM and Shipley P (2004). MICRO-CHECKER: software for identifying and correcting genotyping errors in microsatellite data, Molecular Ecology Notes, 4: 535–538.


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EXPANSION OF THE INVASIVE ALGAE CAULERPA RACEMOSA VAR. CYLINDRACEA (SONDER) VERLAQUE,

HUISMAN & BOUDOURESQUE,2003 ON THE REGION OF VALENCIA SEABED

ABSTRACT

The present study contains the results gathered from the programme monitoring the implantation of invasive species of algae in the Region of Valencia. The programme has been in operation since 1993 and consists of an annual inspection at 40 points considered to be at most risk along the coast, as well as responding to warnings given by entities and individuals. The programme was initially designed to detect the presence of Caulerpa taxifolia (Vahl) C.Agardh 1817, which has not been detected during any of the inspections carried out in the last 15 years. However, C. racemosa var. cylindracea (Sonder) Verlaque, Huisman & Boudouresque, 2003 was detected in 1999, more specifically on the approaches to the Port of Castellón de La Plana and since then it has expanded exponentially and is now present along the coast of all three Valencian provinces, with the area colonised being estimated at 168 Km2

in late 2008. The programme has also detected the presence of other invasive species of algae, namely Asparagopsis taxiformis (Delile) Trevisan de Saint-Léon, 1845 and Lophocladia lallemandii (Montagne) F. Schmitz, 1893, currently present exclusively in the Islas Columbretes archipelago.

INTRODUCTION

Of the more than 70 known species of the genus Caulerpa, only a small number are present in the Mediterranean. Caulerpa taxifolia (Vahl) C.Agardh, 1817 is a tropical species that was first seen in the Mediterranean in Monaco in 1984. Since then it has propagated and covered large areas of the Western and Adriatic areas of the Mediterranean, mainly on the French Cote D’Azur, Monaco and Italy, although colonies have also been detected in Spain (Balearic Islands), Croatia and Tunisia. Since its appearance, the species has expanded rapidly, with the areas occupied multiplying 3 to 10 times a year (Boudouresque, et al., 1996). C. taxifolia is a highly invasive species and has become a serious threat to most Mediterranean marine algae and phanerogamae (Meinesz & Hesse, 1991; Villele & Verlaque, 1994, Verlaque & Frytaire,

(1) Institut d’Ecologia Litoral. C/ Jacinto Benavente, 21.El Campello. 03560. Alicante. España.

(2) Conselleria de Medio Ambiente, Agua y Urbanismo. Dirección General de Calidad Ambiental.C/ Francisco Cubells, 7. Valencia.

Key words: Caulerpa racemosa, invasive algae, expansion, Region of Valencia, Spain, Mediterranean.

JUAN E. GUILLÉN(1), SANTIAGO JIMÉNEZ(1), JOAQUÍN MARTÍNEZ(1), ALEJANDRO TRIVIÑO(1),YOLANDA MÚGICA(1), JOSÉ ARGILÉS(1) & MARISA BUENO(2)

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JUAN E. GUILLÉN, SANTIAGO JIMÉNEZ, JOAQUÍN MARTÍNEZ, ALEJANDRO TRIVIÑO, YOLANDA MÚGICA, JOSÉ ARGILÉS & MARISA BUENO

1994). Highly diverse ecosystems in the invaded areas have been replaced by monospecific populations of C. taxifolia (De Torres et al., 1996). The significant capacity of the species for expansion, either naturally or due to human activities (Meinesz & Hesse, 1991; Meinesz et al., 1993), as well as the cost of eradication (Avon et al., 1994; Escoubet & Brun, 1994; Riera et al., 1994) make the early detection of new colonies essential, as this is currently the best way of slowing the expansion of C. taxifolia in the Mediterranean.

In this sense and after the location in 1991 of a colony of Caulerpa taxifolia at Saint-Cyprien (France), very close to the border with Spain, the Direcció General de Qualitat Ambiental (Department of the Environment of the Regional Valencian Government) started a programme to monitor the coasts of the Region of Valencia to detect the presence or possible implantation of Caulerpa taxifolia. The programme was in force from 1993-1994 and 1996-1998 within the framework of the European Commission LIFE

Figure 1: Monitoring stations in the Region of Valencia.

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EXPANSION OF THE INVASIVE ALGAE Caulerpa racemosa VAR. CYLINDRACEA (SONDER) VERLAQUE,HUISMAN & BOUDOURESQUE, 2003 ON THE REGION OF VALENCIA SEABED.

programmes. Since then, the Region of Valencia Government has remained vigilant and the sale, distribution and commercialisation of algae have been prohibited in the Region of Valencia since May 1994 in order to prevent and reduce the risk of introducing C. taxifolia (Region of Valencia Government Decree 89/1994, dated May 10th).

At the same time, another species of the genus Caulerpa, C. racemosa, is also spreading in many parts of the Mediterranean even faster than C. taxifolia. Although C. racemosa has not been as widely studied as Caulerpa taxifolia, the meeting in

Heraklion (Crete) on invasive species of Caulerpa in the Mediterranean (Report UNEP(OCA)/MED WG. 139/4 dated March 20th 1998) concluded that the strain of C. racemosa that is currently colonising the Mediterranean could show morphological characteristics that differ from one zone to another as well as the specimens described in the same region at the beginning of the century. A molecular study confirmed the hybrid origin of this species (Durand et al., 2002), initially originating from Southwest Australia (C. cylindracea) (Harvey, 1858; Womersley, 1984), recognising this taxon as C. racemosa var. Cylindracea (Verlaque et al., 2003).

Figure 2: Presence of Caulerpa racemosa in the coasts of Castellón and Valencia.

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This species is distributed widely over all the warm regions of the planet (Verlaque et al., 2000). In the Mediterranean, Caulerpa racemosa colonises all kinds of substrate (rock, sand, mud) as well as the dead growth of Posidonia up to 60 metres deep, upsetting coastal marine biocenosis. This successful colonisation is based on its ability to propagate, whether by sexual reproduction or by fragments and propagules that are spread by vessels (ballast water, anchors), fishing (dredging, trawling, trammels) and also by currents (Klein & Verlaque, 2008). The recommendations of the 1998 meeting in Crete highlighted the need to i) give any official instructions needed to prevent those using

the sea from using practices that contribute towards the dissemination of these species, particularly in situ cleaning of anchors, fishing tackle and diving material, to avoid disseminating fragments of these algae in the sea; ii) carry out an inventory and cartographic monitoring of the colonised areas; iii) monitor the evolution of the biocenosis of the affected areas; iv) maintain scientific research into all aspects relating to the species: evolution of consequences and control of their dynamics; v) control, as far as possible, the expansion of the two species, mainly by eradicating small colonies in areas of high patrimonial worth and in regions distant from strongly colonised areas.

Figure 3: Presence of Caulerpa racemosa in the coast of Alicante.

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The Monitoring Plan carried out in the Region of Valencia has been designed to follow said recommendations.


Detection and cartography

The species are monitored annually, coinciding with the period of maximum density and growth of the algae between June and October (Klein & Verlaque,

2008), along the 450-kilometre coastline of the Region of Valencia, at 41 stations regarded as being at risk of the implantation of invasive algae (presence of tourist vessels, merchant shipping, fishing activities) (Figure 1). Most stations correspond to fishing ports, marinas and nearby areas. As well as the ports, the programme monitors traditional anchoring areas along the Alicante coast and areas where the algae have been detected in previous years, as well as acting on any information received from volunteers, divers and fishermen who receive regular information about invasive algae.

Figure 4: Presence of Caulerpa racemosa in 2008.

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Two types of methodology are used: i) Large areas are examined to detect the presence of invasive algae and their bionomic composition is assessed, with a file being drawn up for each of them every year in risk areas nearby to harbours, bays and coves. Transects were surveyed both perpendicular and parallel to the shoreline in deeper areas (from 4 to 35 meters). These tracks are used to establish the spatial distribution of Caulerpa racemosa and to characterise the marine benthic habitats occupied. Video transects are recorded by towing a camera behind a boat along the same courses. The CCD digital camera records the time, date, speed and geographic coordinates on screen; ii) scuba dives in areas of difficult access for the boat, acting on information received. During the inspections, images of the surface affected by the new colonies are taken using a video or still camera. The boundaries of C. racemosa were estimated by interpolation, assuming data transects and benthic habitat map.

Eradication

Eradication of species in a marine environment is difficult, and can only be carried out in closed or semi-closed areas (Bax et al., 2001). Despite this, between 2005 and 2007 action was taken to control and eradicate the shallowest and smallest colonies of Caulerpa racemosa, this being the case with the colonies located in Alicante, La Cala de La Mina (Alfaz del Pí), Torrevieja, Jávea and Tabarca. The method used consists in diluting copper sulphate, according with McEnnulty et al. (2001). Laboratory experiments show that copper concentration of >10 ppm applied for 30 minutes causes complete mortality. Concentrations of copper ions required to cause 100% mortality were 10,000 times lower than those of potassium and sodium ions (Uchimuraet al., 2000). In this case we used a solution of 1 to 5 mg/l of copper, sufficiently saturated in sodium chloride (70‰) to ensure that its increased density meant that it remained in the seabed at the same depth as the colony treated. The solution was prepared in advance and injected over the colonies, which had previously been covered with a plastic sheet

weighted along the edges and fitted with valves for the solution to be injected. The algae remained in contact with the solution for 45 minutes before the plastic was removed.

The effectiveness of the treatment was assessed after four days, rating it in accordance with densities of fronds and stolons fallen in comparison with their state before being treated (100%: total elimination – 0%; no effects). The process was repeated whenever part of a colony was seen to have survived in the treated areas.

RESULTS

Evaluation of the monitoring stations

Every year approximately 50 kilometres of video transects were filmed. The results for 2008 are shown on Table I, where the expansion of Caulerpa racemosa already affects 39% of the stations (16), 51% if we take into account the cases denominated “highly probable” (21 stations). Lophocladia lallemandi and Asparagopsis taxiformis were only detected at one station (2.4%). Only ten years ago, none of the stations had detected any of these algae.

1998 2000 2002 2004 2006 2008 20100

20

40

60

80

100

120

140

160

180

Years

Km2

Figure 5: Areas colonised by Caulerpa racemosa in the Region of Valencia.

Figure 5:Areas colonised by Caulerpa racemosa in the Region of Valencia.

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Presence of Caulerpa racemosa

Caulerpa racemosa was first detected in the waters off the Iberian Peninsula (Castellón) in 1999 (Aranda et al., 1999). Since then, colonisation has progressed at an exponential rate, with no withdrawal having been detected in the areas colonised. The depths at which it is found range from practically on the shore (Cabo de Huertas -Alicante, Playa de los Locos -Torrevieja, Cala de La Mina -Alfaz del Pí and Cabo de Santa Pola), to depths of over 30 metres: 34 metres in Alicante, 32 metres in Benidorm, Elche and Santa Pola.

The size of the areas affected by the invasion of this species on the infralittoral level differs due to their different extent in the north and south of the Region of Valencia: up to 15 metres deep off the coast of Castellón and Valencia, and up to 20 – 25 metres deep in Alicante. It prefers to grow on hard substrates on the biocenosis of calm infralittoral photophilic rock, although it is also frequent in shallow areas where the sea beats against rock. It has also been seen colonising areas of Posidonia oceanica in degradation with scarce coverage and density, as well as on the dead matter of Posidonia oceanica, in this case frequently together with Caulerpa prolifera. This association has also been observed in dense meadows of Cymodocea nodosa. However, in areas with fine sand, where the friction of the sediment can be significant, C. racemosa has not been found. Neither is it found in areas with significant sedimentation of silt, such as inside ports, areas where C. prolifera is frequent.

The circalittoral level is where larger areas have been colonised by Caulerpa racemosa, the biocenosis in which this algae has spread most is the detritic coastal biocenosis, both in its facies of sedimentation and in that of typical appearance. It is also frequent, especially on the Alicante coast, at the lower level of distribution of Posidonia oceanica, when the latter is degraded, largely due to illegal trawling in the area.

The morphologies of colonisation by Caulerpa racemosa are very different at the infralittoral and circalittoral levels. The first sees very rapid growth of stolons with long fronds (up to 12 cm). In this area we have seen types of growth creating a “shrub” some 10 cm thick, due to the superimposition of stolons. In these cases the C. racemosa meadow favours sedimentation and reduces the number of species enormously, especially the macrophytes (Klein & Verlaque, 2008).

However, at depth, at the circalittoral level, Caulerpa racemosa is more conspicuous (fronds no longer than 7 cm) and their density is much less than that seen at the infralittoral level, although it is at this level where we see the greatest surface areas colonised on the coast of the three provinces.

a) Situation on the Castellón coast.

The first zone affected was discovered in July 1999 in waters close to the Grao de Castellón, this being the first mention of this species in the waters around the Iberian Peninsula (Aranda et al., 1999), and was found at the same time in the waters around the Balearic Islands (Ballesteros et al., 1999). It was detected in the Region of Valencia thanks to the many awareness campaigns carried out by the programme aimed at detecting the presence of Caulerpa taxifolia, and which led to the warning being given by recreational divers who notified the presence of the species on the seabed close to Castellón oil refinery. The area was searched thoroughly during the first two weeks of August. A colony was initially located 9 metres deep on dead Posidonia oceanica and precoralligenous communities, the community extended over some 3 m2, largely in a single block, although a search of the surrounding area revealed the presence of numerous small colonies close to the main block over 337 hectares, indicating that the algae had been present for no more than 1 or 2 years and that it was expanding rapidly, probably through the dispersion of fragments from the main colony.

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Said colonies have continued to propagate, mainly in the deeper areas, as more superficial coastlines with a predominance of sandy substrates hinder the expansion of the algae. Currently, the colonies of Caulerpa racemosa cover an area of 72.5 km2. (Figure 3). The presence of the algae has been detected from the shores of Benicàssim to Burriana, although the invaded area is likely to be much greater. The algae are found from the shore and to a depth of 28 metres on bottoms that were previously occupied by meadows of Posidonia oceanica and are now detritic biocenosis with facies of sedimentation. Large amounts of the species are caught in seine nets and even get caught in paternoster lines, making it very difficult to fish in the area.

The presence of the species was also detected four years ago on the Isla Grossa island in the Islas Columbretes.

b) Situation on the Valencian coast.

Along the coast of the province of Valencia, the invasive strain of Caulerpa racemosa has been located close to the Port of Sagunto, with the first colonies being found in 2001. The southward expansion was probably related to the proximity of the colonies of Castellón, and factors as the effect of sea currents and fishing activities.

Caulerpa racemosa is found at mid-depth along muddy detritic coastal bottoms, and dead Posidonia oceanica meadows, areas where seine netting activities are carried out. They currently cover an area of approximately 51 km2 (Figure 3) and have not yet been detected in shallower waters, possibly, as with Castellón, because of the predominance of open, sandy coastlines. Its presence has not yet been detected in the few rocky coastal areas or cliffs (e.g.: Cabo de Cullera).

c) Situation on the Alicante coast.

In early 2000, different colonies of algae were

identified south of the port, at depths of 10-12 metres. In 2001, the species was discovered at Cabo de Santa Pola (Aranda et al., 2003; Aranda, 2004) in shallow water on bottoms with Posidonia oceanica meadows in the degradation stage. The most probable origin in this case is linked to oil tanker mooring points, which coincides with the discovery off the coast of Castellón – oil refinery terminal - and off other ports, such as Marseille. In this case, the first colonies were found around the gas terminal. It could have been spread by the anchors and chains and/or ballast water of the vessels.

A later cartographic survey carried out in late 2002 from the Port of Alicante to Cabo de Huertas, and another in early 2003 towards the southern part of the port, showed that almost 10 km2 were affected by the species, affecting over 18 km of the coast between Cabo de Huertas and Cabo de Santa Pola, as well as the sector with degraded Posidonia oceanica at a depth of 25 to 30 metres between Cabo de Huertas and El Campello. In Alicante Bay, the algae has colonised both degraded Posidonia meadows with a low density of shoots – due to cargo vessels mooring in the bay - and muddy detritic bottoms. Its depth varies from 15 to 34 metres. It has propagated both to the south, on the coast of Santa Pola, reaching the Tabarca Marine Reserve (2006), and to the north, also on detritic bottoms, from 32 to 25 metres deep facing the San Juan and Muchavista beaches (2004), Isla de Benidorm (2005) and the deep coast off Villajoyosa (2006).

The above-mentioned areas account for most of the colonisation of Caulerpa racemosa along the coast of Alicante (almost 45 km2 in 2008) (Figure 4). Its morphology consists of a reduced density of short fronds with long stolons. As well as these colonies, every year since 2003 the coastlines with cliffs in Alicante have seen the appearance of colonies of C. racemosa, with these having a very different morphology, much more invasive growth, and higher density of very long (up to 12 cm) fronds that cover and grow on the algae substrates that characterise the

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Station. Year 2008 C. taxifolia C. racemosa A. taxiformis L. lallemandi

1. Vinaroz 0 0 0 0

2. Benicarló 0 0 0 0

3. Peñíscola 0 0 0 0

4. Oropesa 0 0 0 0

5. Castellón 0 1 0 0

6. Burriana 0 1 0 0

7. Sagunto 0 1 0 0

8. Pobla de Farnals 0 1 0 0

9. Valencia 0 1 0 0

10. Cullera 0 0 0 0

11. Gandía 0 0 0 0

12. Denia 0 0 0 0

13. Jávea 0 1 0 0

14. CalaSardinera (Jávea) 0 1 0 0

15-16. San Martín Cape (Jávea) 0 1 0 0

17. Ambolo Island (Jávea) 0 0* 0 0

18. Cala Granadella (Jávea) 0 0 0 0

19. Moraira (Teulada) 0 0 0 0

20. Calpe 0 0 0 0

21. Puerto Blanco (Calpe) 0 0 0 0

22. Mascarat (Altea) 0 0 0 0

23. Altea 0 0* 0 0

24. Cala La Mina (Altea) 0 1 0 0

25-26. Sierra Helada (Alfaz del Pí) 0 0 0 0

27. Benidorm 0 1 0 0

28. Cala de Finestrat 0 0* 0 0

29. Racó del Conill (Villajoyosa) 0 0* 0 0

30. Villajoyosa 0 0 0 0

31. El Campello 0 1 0 0

32. La Albufereta (Alicante) 0 1 0 0

33. El Postiguet (Alicante) 0 0* 0 0

34. Port of Alicante 0 1 0 0

35. Santa Pola 0 0* 0 0

36. Tabarca Island (Alicante) 0 1 0 0

37. Torrevieja 0 1 0 0

38. Cabo Roig (Torrevieja) 0 0 0 0

39. Campoamor (Orihuela) 0 0 0 0

40. Pilar de la Horadada 0 0 0 0

41. Columbretes Islands Castellón) 0 1 1 1

Total presence 0 16 (21 incl. probables) 1 1

% stations 0 39,00% (51% probables) 2,40% 2,40%

Table I: Evaluation of the Monitoring Plan.. 1 mean presence, 0 absence, y 0* presence without confirmation.

Table 1: Evaluation of the Monitoring Plan.. 1 mean presence, 0 absence, y 0* presence without confirmation.

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biocenosis of the infralittoral rock, or the blanket of Posidonia oceanica, especially when the latter is receding. These colonies are listed in Table II.

The expansion of the colonies at infralittoral levels is sometimes spectacular, as was the case of the Isla de Benidorm, where it started with a colony of less than 30 m2 close to the mooring lines at a depth of 15 metres in 2005. By 2006, the colonies had colonised part of the southwest sector of the island to a depth of approximately 8 metres, especially in depths of up to 20 metres, covering an area of 13,000 m2. A year later, the surface colonised extended from

8-10 metres to 30 metres in depth, over the whole west-southwest sector, especially from a depth of 15 metres, covering an area of almost 120,000 m2. In 2008, the colonies made special progress at the deeper levels, being found from 15 to 30 metres, and in the northern and southern parts.

Eradication actions

In accordance with the recommendations of the Crete Meeting, concerning “Controlling, as far as possible, the expansion of the two species, mainly by eradicating small colonies in areas of high patrimonial

Location Detection (year)

Surface State and Response

Cala de La Mina (Alfaz del Pí) 2004 400 m2 Treatments in 2004, 2005 and 2006, eliminated in the shallow area, now on the cliff.

Huertas Cape (Alicante) 2004 8000 m2 Located in very shallow bays. Continuity in the deep grass to -19 m deep.

Benidorm (Island) 2005 120.000m2 Initially around trains anchoring subsequently colonized all funds detrital around the island

Tabarca (colonies and areas near the village, and “La Galera” area )(Alicante)

2005 2.000 m2 Expanding

Tabarca (“la Llosa” area) (Alicante) 2005 4.000 m2 Areas of degradation in Posidonia oceanica meadow (areas affected by the dragging effect of the buoy's chain).

Cala Blanca (Jávea) 2006 1.500 m2 Treatments in 2006. The expansion continues.

Torrevieja (Bays of: El Cura, La Calita, and Los Locos)

2006 100 m2 2006. Partially removed.

Isla del Portitxol (Jávea) 2007 500 m2 Very irregular relief.

Benidorm (Rincón de L'Oix) 2007 50 m2 Low growth.

El Amerador (El Campello) 2008 100 m2 In areas with degradated Posidonia oceanica meadow.

Torres River (Villajoyosa) 2008 200 m2 In areas with degradated Posidonia oceanica meadow.

Table II: Location of Caulerpa racemosa colonies (surface of less than 10.000 square meters). State after algaecides treatment.

Table 2: Location of Caulerpa racemosa colonies (surface of less than 10.000 square meters). State after algaecides treatment.

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worth and in regions distant from strongly colonised areas”, from 2004 to 2007, a number of steps were taken to eradicate small colonies at infralittoral levels in reserves, natural parks and areas of interest. The eradications consisted of the controlled diffusion of algaecides over areas measuring 1 m2. The results can be seen in Table III, and were highly effective, with an average 92.7% success rate for eradication. However, the high cost and length of time involved in using this technique, when compared with the high colonisation rate of Caulerpa racemosa, mean that these kinds of measures are not viable at present.

Other species of invasive algae

Other species of algae regarded as invasive as a result of their potential negative effects on the biocenosis of the areas where they settle, as they displace other members of the algal community, were: i) Asparagopsis taxiformis: detected in the Islas Columbretes in 2007: L’Illa Grossa, Foradada and Ferrera, at over 20 metres deep, both in rocky areas corresponding to hemiphotophilic and sciaphilic communities of the infralittoral rock and in areas of coarse sand and gravel, as well as communities at circalittoral levels; ii) Lophocladia lallemandi: detected in the Islas Columbretes in 2007, covering bottoms with communities of superficial photophilic algae of the infralittoral rock in the area of L’Ila Grossa. Colonisation of these algae is massive and this species also coexists with Caulerpa racemosa.

CONCLUSIONS AND DISCUSSION

Since the start of the Plan for monitoring the presence of invasive algae in the Region of Valencia, Caulerpa taxifolia has not been located as yet. On the contrary, since its detection in 1999, C. racemosa, has continued to expand along the Valencian coast, especially in large areas at circalittoral levels, as well as at numerous points at infralittoral levels of the Alicante coast in shallow waters. We currently estimate that the area covered by the algae is approximately 168 Km2 (Figure 5, Table IV), with differing density.

This means that the greatest density occurs at depths of less than 20 metres, while greater areas are covered at greater depths, but with lower density.

The increase in awareness thanks to the publication of leaflets and reports aimed at divers, rangers, fishermen and volunteers has been very useful for obtaining information about such a large area, given the apparently random appearance of new colonies.

Of the 16 stations in the Region of Valencia that have detected the presence of Caulerpa racemosa, there are stations close to major cities (Castellón, Alicante) and ports with sea traffic (Sagunto), as well as in areas of high environmental value (Tabarca, Columbretes). This means that there is no direct correlation between polluted areas and the presence of C. racemosa. Neither has it been found inside dense Posidonia oceanica meadows, but it has been found around their edges, in line with other sightings made in the Mediterranean (Klein & Verlaque, 2008).

The increase of bottom surface covered or colonized by Caulerpa racemosa was estimated in 17 km2/year. These rates being higher than those seen on the French coast, where the area affected doubled every year (Ruitton et al., 2005; Javel & Meinesz, 2006). We have recently seen the sudden collapse of C. racemosa meadows in certain areas of France and Turkey, although these variations could be due to unfavourable situations, such as extreme temperatures, abrasion by sediment, high hydrodynamics or even massive reproduction (Klein & Verlaque, 2008). This means that we cannot at present define any guideline to indicate stabilising the colonisation curve of C. racemosa in either the Mediterranean or the Region of Valencia.

In the region of Valencia, as in other areas of the Mediterranean, the areas where the algae are implanted are often degraded or degrading biocenoses, mainly Posidonica oceanica meadows with limited coverage of degraded or dead matter – and detritic coastal biocenoses, mainly in their

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facies of sedimentation, except for the colonies in the Tabarca marine reserve and the Islas Columbretes, where we can also see colonisation by Lophocladia lallemandi and Asparagopsis taxiformis, both recently, since 2007. Several studies have confirmed a decrease in the total number of species and the total coverage of macrophytes in all the biocenoses where Caulerpa racemosa has installed itself, but especially in rock biocenoses, with the effects being very similar to those caused by hypersedimentation stress, showing that one of the most damaging effects is that sedimentation processes over rocky substrates are favoured (Piazzi et al., 2005).

The first introductions nuclei are related with harbours and ballast water (Castellón and Alicante). However, nowadays the main dissemination vectors of Caulerpa racemosa are related to fishing activities and sea currents. We can see a clear correlation in its expansion with seine net fishing, with the deep areas where the algae are implanted, close to the lower limit of Posidonia oceanica meadows or in the detritic biocenosis, largely corresponding to the grounds for this type of fishing, which disturbs the bottom and moves through the area, thus favouring the re-implantation of the fragments adhered to the nets. The fragmentation of Caulerpa racemosa favours its spread, with fragments surviving for several days until they are fixed in the substrate (Cecherelli & Piazzi, 2001). Paradoxically, this association with seine net fishing is very harmful for the latter, as Italian experience has shown that the fishermen can suffer severe injuries when raising nets full of algal stolons (Magri et al., 2001).

Other areas where colonies have been found include coves and mooring buoys, where the fragments broken off can settle in the mooring areas. This effect has also been seen near mooring sites located near meadows that had been degraded in this way, this being the case of La Cala de La Mina and La Isla de Benidorm, and on other occasions, without meadows, as is the case with the Islas Columbretes.

Despite the success of the eradication programmes, with 92.17% of the algae eliminated after treatment, these control measures are not enough to limit or eliminate the colonisation and expansion of Caulerpa racemosa. This is due to the high cost of eradication that demands at least 2 divers plus support vessels working for no less than 2 hours to eradicate some 10 m2, as opposed to the high growth rate of the algae and the many new outbreaks. This means that we cannot yet use control mechanisms, due to the diffuse limits of the meadows, the difficulty in finding new colonies and the significant capacity for expansion of the species. Some writers believe that more research should be done on the populations originating from Australia to identify their predators, diseases and parasites and build a knowledge base to acquire tools for controlling the algae in the Mediterranean (Klein & Verlaque, 2008).

ACKNOWLEDGEMENTS

We would like to thank the rangers at the Isla de Tabarca Marine Reserve, especially the biologist Felio Martínez, and the rangers at the Islas Columbretes Nature Park, particularly the biologist, Diego Kergstin. We should also mention all the voluntary contributions made by divers, fishermen and other volunteers who have collaborated with the programme over the last 15 years.

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151

IMPLEMENTATION OF AN OPERATIONAL OCEANO-METEOROLOGICAL SYSTEM FOR THE BASQUE COUNTRY

ABSTRACT

In this contribution, the most relevant aspects of the ITSASEUS project are shown. Under this acronym, several works are carried out by the partners (EUVE and AZTI-Tecnalia) in order to implement an operational oceano-meteorological system for providing daily a 72-hour forecast for the Basque Country region and its influence areas. The system combines meteorological, wave and hydrodynamic modelling at several scales together with field observations. The meteorological model used is the MM5 mesoscale model with a nested domains configuration, in which the GFS (Global Forecast System) is used for providing the lateral and initial conditions. The wave and hydrodynamic models used are the Wavewatch-III and ROMS, respectively.

Preliminary results are promising and show the forecast subsystems ability to predict oceano-meteorological variables in the Basque Country region.

INTRODUCTION

The sinking of the oil tanker Prestige off the coast of Galicia (in the northwestern part of Spain), in 2002, was the base to establish in the Bay of Biscay operational oceano-meteorological systems. During the Prestige crisis, the most powerful European Institutions were able to give a quick response to the catastrophe. Other institutions, without an extensive experience in this type of events, had to generate practical systems in order to help to the governments and local authorities in the control of the oil spills. Systems, such as the one developed by EUVE and AZTI-Tecnalia for the Basque Country (González et al., 2005), demonstrated their suitability to the management of the oil pollution.

The pressure generated on public administrations during the Prestige crisis, together with the progressive interest of the society on environmental problems (both in the atmosphere and ocean), resulted in financial support for a huge range of projects, such as: EuroGOOS (European co-operation on the Global

Key words: Meteorological modelling, wave modelling, hydrodynamic modelling, operational oceano-meteorology, Bay of Biscay,

Basque Country.

S. GAZTELUMENDI(1,2), M. GONZÁLEZ(3), J. EGAÑA(1,2), A. RUBIO(3), I.R. GELPI(1,2), A. FONTÁN(3),K. OTXOA DE ALDA(1,2), L. FERRER(3), N. ALCHAARANI(1,2), J. MADER(3) & AD. URIARTE(3)

(1) Basque Meteorology Agency, EUSKALMET, Parque Tecnológico de Álava, Avda. Einstein 44, Ed.6 Of. 303, 01510, Miñano, Álava, Spain, www.euskalmet.euskadi.net.

(2) Meteorology Division, EUVE Foundation, Avda. de los Hue-tos 79, 01010, Vitoria-Gasteiz, Álava, Spain, www.euve.org.

(3) Marine Research Division, AZTI-Tecnalia, Herrera Kaia – Portualdea z/g, 20110, Pasaia, Gipuzkoa, Spain, www.azti.es

email: [email protected]

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S. GAZTELUMENDI, M. GONZÁLEZ, J. EGAÑA, A. RUBIO, I.R. GELPI, A. FONTÁN, K. OTXOA DE ALDA, L. FERRER, N. ALCHAARANI,J. MADER & AD. URIARTE

Observing System); ECOOP (European COastal-shelf sea OPerational observing and forecasting system); ESEOO (Establishment of a Spanish Operational Oceanography System); and LOREA (Litoral, Océano y Riberas de Euskadi-Aquitania). All these projects are centred on providing useful tools, for the atmosphere and ocean, through operational systems which combine data acquisition together with numerical modelling.

ITSASEUS is a research project with the same purposes of the aforementioned projects, developed for the Basque Country region (in the northern part of Spain). The project, included within the Framework of ETORTEK Programme, is funded by the Department of Industry, Trade and Tourism and the Department of Transport and Public Works of the Basque Government. It brings together meteorological and oceanographic institutions (EUVE and AZTI-Tecnalia), with the objective of improving the way in which the oceano-meteorological services are working presently and merging the products in an unique operational system. This system will be maintained by Euskalmet (Basque Meteorology Agency).

METHODOLOGY

Meteorological subsystem

The meteorological subsystem is based upon the implementation of a mesoscale model, using techniques of progressive nesting. At present, GFS meteorological model (Global Forecast System) is used to provide the initial and boundary conditions for the limited-area mesoscale model MM5 (Fifth-Generation NCAR / Penn State Mesoscale Model).

GFS is a global numerical weather prediction model developed by NCEP (National Centre for Environmental Prediction; Kanamitsu et al., 1991; Caplan et al., 1997). At present, the model runs four times a day (00, 06, 12 and 18 UTC) and provides forecasts up to 16 days in advance. Vertically, the model divides the atmosphere into 64 layers. Temporally, it provides forecasted fields for every 3 hours.

MM5 is a limited-area, non-hydrostatic, terrain-following sigma-coordinate model designed to simulate

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Figure 1. Four nested domain topographies used in the meteorological subsystem. Figure 1: Four nested domain topographies used in the meteorological subsystem.

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or predict mesoscale and regional-scale atmospheric circulation (Grell et al., 1994). We define 23 vertical non-equidistant sigma levels, with better resolution in the boundary layer, where four levels are defined in the first 100 m. Non-hydrostaticity limit pressure gradient forces errors in complex terrain, but it allows the model to be used at a few-kilometre scale.

Four domains at different resolutions are used: (1) North Atlantic domain with 160x195 grid points and 81 km resolution; (2) European North Atlantic domain with 175x196 grid points and 27 km resolution; (3)

Bay of Biscay domain with 199x199 grid points and 9 km resolution; and (4) Basque Country domain with 190x208 grid points and 3 km resolution (see figure 1). This configuration cover the area of interest with increasing resolution considering two-way nesting interactions. This means that the input for the nested grid from the coarse mesh comes via its boundaries, while the feedback to the coarser mesh comes from the information provided by the interior of the nested grid. As a result, we obtain some meteorological fields for defined mesoscale domains, including wind, air temperature, precipitation rate, relative

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Figure 2. Examples of products from meteorological subsystem. Wind surface map (km/h) (upper image) and meteogram HR: relative humidity, T(2m): air temperature at 2 m (ºC), T(sfc): surface temperature (ºC), dirV: wind direction (degrees), V(km/h): wind speed (lower image).

Figure 2: Examples of products from meteorological subsystem. Wind surface map (km/h) (upper image) and meteogram HR: relative humidity, T(2m): air

temperature at 2 m (ºC), T(sfc): surface temperature (ºC), dirV: wind direction (degrees), V(km/h): wind speed (lower image).

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humidity, and long and short wave radiation fluxes at the surface level.

Terrain elevation comes from the United States Geological Survey (USGS) global digital elevation model (DEM) with a horizontal grid spacing of 30 arc seconds. Those data and land use data are horizontally interpolated, using a 2-dimension parabolic interpolation to the mesh of each domain. Surface properties such as albedo, roughness length, long wave emissivity, heat capacity and moisture availability are determined through land-use data. Each grid cell of the model is assigned with one of the 24 land-use categories. These values are variable according to summer or winter season.

The meteorological subsystem is conformed by many pre/post-processing subprograms and shell scripts that work in a coordinated way. These programs adequate initial and lateral conditions coming from the global model, execute the limited-area model for the telescopic domains, and adequate

numerical results to different graphical and ASCII formats for their analysis. A couple of programs based on GrADS and shell scripts are developed in order to adequate numerical outputs for analysis and validations, and to put them in different formats, useful to final users.

Generated ASCII tables with different meteorological variables at different points, times and levels are suitable to be used in any spread sheet or data base program for analysis purposes. Many graphical results representing wind time evolution or surface wind maps are also provided (see figure 2). Post-processing tools also provide some meteorological fields in NetCDF format and WW3-ASCII for hydrodynamic and wind wave model input.

There is a minimum amount of real-time coarse data required to run the meteorological subsystem: sea level pressure, SST and wind components, temperature, relative humidity at surface and at 1000, 850, 700, 500, 400, 300, 250, 200, 150, 100 mb levels.

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Figure 3. Main hydrodynamic characteristics of the Bay of Biscay (adapted from Ferrer et al., 2009) and limits of the spatial domains of the configurations used for the ROMS model (dashed lines).

Figure 3: Main hydrodynamic characteristics of the Bay of Biscay (adapted from Ferrer et al., 2009)and limits of the spatial domains of the configurations used for the ROMS model (dashed lines).


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Meteorological subsystem runs on a Linux environment twice daily based on 00 UTC and 12 UTC GFS data for a period of 96 hours. This subsystem is running pre-operationally in a parallelized 64 CPU Cluster system at the Basque Meteorology Agency (Euskalmet). Present configuration is not definitive and depends on final results from validation and pre-operational activities, and from coming improvements in the operational meteorological numerical forecast system in Euskalmet (Gaztelumendi et al., 2007).

Hydrodynamic subsystem

The hydrodynamic subsystem used to determine current, temperature and salinity fields, for the coastal and oceanic regions of the Basque Country, is based on the Regional Ocean Modeling System (ROMS). ROMS is an evolution of the S-coordinate Rutgers University Model (SCRUM), as described by Song and Haidvogel (1994). It has been expanded to include a variety of new features, such as: high-order advection-schemes; accurate pressure gradient

algorithms; several subgrid-scale parameterizations; atmospheric, oceanic, and benthic boundary layers; biological subsystems; radiation boundary conditions; and data assimilation.

The numerical aspects of ROMS have been described in detail by Shchepetkin and McWilliams (2005). ROMS has been used to model water circulation in a variety of regions of the world ocean, ranging from global to local scale (e.g. Haidvogel et al., 2000; Malanotte-Rizzoli et al., 2000; She and Klinck, 2000; MacCready and Geyer, 2001; Penven et al., 2001; Marchesiello et al., 2003; Di Lorenzo et al., 2004). More recently, several works with ROMS have been done for its establishment in an operational mode in the Bay of Biscay and the Basque Country region, using different forcing and climatological databases (González et al., 2007; Ferrer et al., 2007, 2008, 2009).

In the pre-operational subsystem configuration, the spatial domain of the Basque Country region

Figure 4: Four nested domain bathymetries used in the wave subsystem. North Atlantic (NA),East North Atlantic (ENA),Bay of Biscay (BB) and Basque Country (BC).


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extends from 43.2º to 45ºN and from 5.3º to 1.1ºW, with a mean horizontal resolution of 2.2 km. This domain is nested into a coarse grid (mean horizontal resolution of 6.6 km), which covers the Bay of Biscay, from 41.6º to 48ºN and from 10.8º to 0.8ºW (see figure 3). Vertically, the water column is divided into 32 sigma-coordinate levels; these are more concentrated within the surface waters, where most of the variability occurs; this, in turn, retains high resolution for the sea surface

processes. The bathymetry used in the model has been obtained by interpolation, following optimisation analysis, of the ETOPO2 (2 minute digital Elevation Topographic model), GEBCO (General Bathymetric Chart of the Oceans), and IBCM (International Bathymetric Chart of the Mediterranean) data sets. This approach has been adopted to obtain a realistic bathymetry, which has been smoothed to ensure stable and accurate simulations (Haidvogel et al., 2000).

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Figure 5. Examples of significant wave height (m) together with wind at 10 m height (knots) map (upper image) and peak period (s) and peak direction map (lower image) with data from ENA and BB domains for 26/04/09 18:00 in the wave subsystem.

Figure 5:Examples of significant wave height (m) together with wind at 10 m height (knots) map (upper image) and peak period (s)

and peak direction map (lower image) with data from ENA and BB domains for 26/04/09 18:00 in the wave subsystem.


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The surface forcing inputs used in the model are provided by the meteorological model. The spatial and temporal resolutions of these data, for its use in ROMS, are 9 km and 3 h, respectively. The variables used are: wind and air temperature at 10 m and 2 m above sea level, respectively; precipitation rate; relative humidity; and long and short wave radiation fluxes. The air-sea heat and momentum fluxes are calculated using the bulk formulae of Fairall et al. (1996, 2003). The river discharges are not included in the present configuration of the model; but they have shown their fundamental role in the coastal area under extreme snowstorms and rainfalls (Ferrer et al., 2009).

The conditions applied to the open boundaries of the coarse grid of the Bay of Biscay are a combination of outward advection and radiation, together with flow-adaptive nudging, towards prescribed external conditions (Marchesiello et al., 2001). These external conditions are estimated using monthly climatological data (Levitus and Boyer, 1994; Levitus et al., 1994), which are used also for establishing the initial conditions. These conditions have been selected in order to run the pre-operational subsystem with smoother data than those provided by other databases for this area (such as MERCATOR or ESEOO). For the finer grid which covers the Basque Country region, the boundary conditions are provided by the results obtained from the coarse grid.

For the tidal forcing, data from the TOPEX/Poseidon Global Inverse Solution Version 5.0 (TPXO.5), developed by Oregon State University, are used. This is a global model for ocean tides, which best-fits (in a least-squares sense) the Laplace Tidal Equations and along-track averaged data, from the TOPEX/Poseidon orbit cycles (Egbert et al., 1994). The tides are provided as complex amplitudes of Earth-relative sea surface elevation and tidal currents, for 8 primary harmonic constituents (M2, S2, N2, K2, K1, O1, P1 and Q1). These harmonics are introduced into ROMS through the open boundaries, using the Flather condition (Marchesiello et al., 2001).

Wave subsystem

The wave subsystem provides forecasts of wave variables at several scales, working with input forcing obtained from the meteorological model. The model is based upon the Wavewatch-III (WW3) model. WW3 (Tolman, 1997, 1999, 2002) is a third generation wind-wave model developed by NOAA/NCEP.

WW3 solves the spectral action density balance equation for wavenumber-direction spectra. Wave energy spectra are discretized using a constant directional increment (covering all directions), and a spatially varying wavenumber grid. The number of frequencies and directions considered are 25 and 24,

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Figure 6. Marine observation system for the Basque Country region.

Figure 6: Marine observation system for the Basque Country region.


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respectively; the frequency increment factor is 1.1 Hz and the first frequency is 0.04118 Hz.

Four domains at different resolutions are used: (1) North Atlantic area (NA) with 151x78 grid points (100ºW-35ºE, 0º-69.3ºN) and 0.9º resolution; (2) European North Atlantic area (ENA) with 133x88 grid points (29.8ºW-9.8ºE, 34.9º-61ºN) and 0.3º resolution; (3) Bay of Biscay (BB) with 151x103 grid points (15.1º-0.1ºW, 41.8º-52ºN) and 0.1º resolution; and (4) Basque Country region (BC) with 166x91 grid points (6º-0.5ºW, 43º-46ºN). The required input data for bathymetry is obtained interpolating GDEM data (National Geophysical Data Center) with 2-minute resolution, for each domain grid (see figure 4).

In pre-operational implementation, the model uses a first order scheme for spatial propagation. For the source terms, the model uses the following options: wind wave interactions and dissipation from WAM-3, non-linear wave-wave interactions from Discrete

Interactions Approximation (DIA, Hasselmann et al., 1985) and wave bottom interactions from empirical linear JONSWAP (Hasselmann et al., 1973) bottom friction parameterization. The source terms are integrated in time using a dynamically adjusted time stepping algorithm, which concentrates computational efforts in conditions with rapid spectral changes.

The model input used for a given domain is: bathymetry, winds every 3 hours, boundary conditions from mother domain (not for the bigger one), and a restart file with information from the previous execution as initial conditions. Output consists on boundary conditions for nested domains and restart files for future execution and selected data in different formats every hour. At present, the sea current and temperature fields are not introduced into the model. Post-processing subsystem includes areal map generation for the desired time interval, spectral representations, ASCII products generation and some products for validation purposes.

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Figure 7. Wind speed (m/s) registered at the station 62163 (Brittany buoy, UK Met Office and Meteo France) versus forecasted values for the meteorological domain 3 in the pre-operational real-time forecast, between 21/04/08 and 13/05/08: time-series (upper image) and scatterplot (lower image).

Figure 7: Wind speed (m/s) registered at the station 62163 (Brittany buoy, UK Met Office and Meteo France) versus forecasted values for the meteorological domain 3 in the pre-operational real-time forecast, between 21/04/08 and 13/05/08:

time-series (upper image) and scatterplot (lower image).


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Significant wave height and wind, peak direction and period and mean direction, period and length map representation for four domains are available every hour (figure 5). Distribution of wave energy over wave directions and frequencies at buoy locations are available in different domains. In this representation spectrum, wind-wave interactions, nonlinear wave-wave interactions, dissipation and sum of selected sources are shown.

A shell script is used for automatic subsystem execution twice daily for 00 and 12 UTC, for 96 hours. Wind wave forecast subsystem runs parallelized on the same PC-cluster used for the meteorological subsystem.

Data analysis

At local level, terrestrial and marine observation systems available in the area are used for comparisons with the model results. At present, the marine

observation system for the Basque Country (see figure 6) keeps 6 coastal stations and 2 offshore (450 and 550 m depth) buoys, measuring some oceanographic and meteorological parameters, together with a HF Radar array. On the other hand, a meteorological automatic weather station mesonet provides meteorological variables data over more than 80 places in the Basque Country area (Gaztelumendi et al., 2003), complemented with a Dual Doppler Meteorological Radar and a Coastal Wind profiler (Gaztelumendi et al., 2006). At global and regional levels, observed data come from buoy, synop, metar and raobs, where they are available. This information is complemented for different purposes with satellite derived data.

In order to evaluate the performance of the system, we use a daily basis verification for main forecasted variables. Several indexes and strategies are used (for meteorological, hydrodynamic and wave subsystems) to make qualitative and quantitative validations based upon registered data.

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Figure 8. Significant wave height (m) registered at the station 62163 (Brittany buoy, UK Met Office and Meteo France) versus forecasted values for the BB domain in the pre-operational real-time forecast, between 21/04/08 and 13/05/08: time-series (upper image) and scatterplot (lower image).

Figure 8: Significant wave height (m) registered at the station 62163 (Brittany buoy, UK Met Office and Meteo France) versus forecasted values for the BB

domain in the pre-operational real-time forecast, between 21/04/08 and 13/05/08: time-series (upper image) and scatterplot (lower image).


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For daily execution, the verification strategy is based upon subjective and objective validations. The first option uses human subjective analysis of available maps for different domains compared with the results of other centres and satellite derived data. The second is based upon automatic point comparison of available variables (mainly wind, significant height and peak period) for selected buoys and meteorological stations in the different domains versus point data extracted from forecast grid.

The validation of numerical results should comprise a reliable estimation of the true value of a quantity, against which simulated data may be compared. In the case of gridded numerical data, there is no unique procedure allows us to validate numerical results by comparison with observations. We need to quantify the ability of the numerical forecast to correctly predict the situation observed, which means that we need some kind of verification statistics. An automatic validation system that uses some familiar continuous statistics like bias, root-mean-square error and the correlation coefficient for meteorological, wave and hydrodynamic subsystems is being implemented.

Punctual validation consists on the estimation of the forecasted variable at the same place where there is data. This is done when we want to compare at a particular location, wind direction and module, temperature or pressure in the mesoscale meteorological model case and wave parameters from the wave model. In these cases, values at the station location from the gridded numerical data are obtained using a bicubic spline interpolation method. Areal validation is also considered, at first instance through visual inspection of different fields among some satellite derived products.

In the meteorological subsystem validation case, the main objective is to reproduce in the more accurate way, the surface wind fields for different meteorological situations. For this purpose, 30 different scenarios, representative of 5 different

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Figure 9. Comparisons model-observations for the annual Sea Surface Temperature (SST, ºC), for 2007 and the Bay of Biscay configuration: (a) mean sea surface temperature from satellite observations and (b) from the simulations with the ROMS model; and (c) Root Mean Square errors (RMS, ºC).

Figure 9:Comparisons model-observations for the annual Sea Surface

Temperature (SST, ºC), for 2007 and the Bay of Biscay configuration: (a) mean sea surface temperature from satellite observations and (b)

from the simulations with the ROMS model; and (c) Root Mean Square errors (RMS, ºC).


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meteorological patterns typical for the Basque Country area, considering sea wave generation effects, are used. Punctual validation is done for wind, temperature or pressure at the same locations where instrumentation is available at all scales.

In the implementation and tuning processes for wave subsystem, executions over some selected scenarios are considered. In this case, a validation strategy is based upon buoy point comparison of different parameters, taking 30 cases selected from 5 relevant weather types that configure local behaviour in the Basque maritime area. This event classification considers 5 categories: strong maritime wind with high fetch (A scenarios) and low fetch (B scenarios); weak wind with swell (C scenarios) and high swell (D scenarios); and offshore wind affecting the Basque area (E scenarios).

For the hydrodynamic model, the initial validation has been carried out using the Sea Surface Temperature (SST) data from satellite and those provided by the offshore buoys of the Department of Industry, Trade and Tourism of the Basque Government (Matxitxako and Donostia buoys, see location in figure 6). Model-data comparisons have been performed for the 2007 year. For this hindcast analysis, NCEP reanalysis data have been used as atmospheric forcing. SST data are obtained from the Advanced Very High Resolution Radiometer (AVHRR) sensor on board of the AQUA/MODIS satellite, working since 2002, and processed to obtain daily images. This is an L3 product which includes radiometric and atmospheric corrections and the application of standard algorithms to obtain the

surface temperature and the geometric projection of the images. Taking into account the hour in which the satellite covers the Bay of Biscay, the images are representative of the sea surface temperature between 12:30 and 14:30 UTC. The spatial resolution of the satellite images is 1.8 km. The Root Mean Square (RMS) and Mean Relative Difference (MRD), estimated as

respectively, are used for the model–observations comparisons. Here, X is the variable and N is the number of data.

RESULTS

For the meteorological subsystem, although the complete set of simulations is not concluded, preliminary results show that wind fields are usually well resolved. When strong winds are present due to synoptically driven forces, good initialization and boundary conditions from global model are essential. Minor differences are observed from lower and medium resolution data. In local driven situations, the lower resolution simulation solves well sea breezes and local patterns flow in the coastal area. In figure 7, we can see, as an example, graphical plot for simulated versus registered wind data for a pre-operational forecast period.

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Figure 10. Monthly Sea Surface Temperature (SST, ºC) from satellite observations (thin black line) and from the simulations with the ROMS model (thick black line), and Root Mean Square errors (RMS, ºC, grey line), integrated for the Bay of Biscay for 2007.

Figure 10: Monthly Sea Surface Temperature (SST, ºC) from satellite observations (thin black line) and from the simulations with the ROMS model

(thick black line), and Root Mean Square errors (RMS, ºC, grey line), integrated for the Bay of Biscay for 2007.

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Some preliminary results for wind wave model in its pre-operational implementation show that the use of high resolution wind fields is important in coastal areas. However, medium resolution is enough in deep water areas far from the coast. Results from higher resolution domains are better in strong wind situations. For the operational wind-wave model, available data from previous execution cycle is critical; if some discontinuity is produced, wave fields for first simulated hours are not correctly forecasted. We obtain a good general behaviour for all domains, and generally minor differences between NA and ENA domains. We obtain relatively good results for BB (even NA) for deep water buoys. At first instance, as we have better resolution winds from higher resolution domains, we obtain better results for BB and BC, especially in windy cases and near the coast. In all scenarios, proper wind fields and initialization are always crucial (see figure 8).

For the hydrodynamic model, comparisons with SST satellite observations in the Bay of Biscay have been carried out for the year 2007 (figure 9). The spatial average of RMS errors (point to point differences between the modelled and observed SST) show mean values below 1.2 ºC. In general, in the open basin, the RMS error is between 0.6 and 0.9 ºC. Locally, higher RMS errors (around 1-1.2 ºC) can be

observed in the coastal area. That is, for instance, the case of the French coast and the corner of the Bay of Biscay. Here, the resolution of the atmospheric forcing used for this hindcast case, the NCEP reanalysis data, is too coarse to predict with accuracy coastal processes. Therefore, the incorporation of the higher resolution data provided by Euskalmet should improve the results between the model and observations.

Over the French Armorican shelf break and slope, around 4-5ºW and 47ºN, occurs the highest RMS error. This is an area characterized by strong tidal currents and the generation of large-amplitude internal tides, due to the interactions of the tide with the bathymetry (Puillat et al., 2004). The presence of a cold thermal front over the slope has been related to the effect of the internal tide and the wind-induced mixing (Serpette and Maze, 1989). Differences between the model and observations over this area could be related to these processes and require further investigation.

Figure 10 shows the monthly evolution of the spatial average of the SST for the Bay of Biscay from satellite observations and ROMS model, together with the RMS errors. The SST evolution for the observations and ROMS model is similar and shows the seasonal surface heating/cooling cycle. Maximum

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Figure 11. Time-series of vertical temperature profile (ºC) for 2007, between sea surface and 200 m depth at the Donostia buoy: (a) data registered by the buoy; and (b) obtained from the ROMS model.

Figure 11: Time-series of vertical temperature profile (ºC) for 2007, between sea surface and 200 m depth at the Donostia buoy: (a) data registered by the buoy;

and (b) obtained from the ROMS model.


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integrated SST occurs in August (around 19 ºC) and a minimum value is reached in February (approx. 12 ºC). RMS errors are maximum from March to September (0.75-1 ºC); during the rest of the year, errors are below 0.75 ºC.

Comparisons with the time-series of the vertical temperature profile at the Donostia buoy (figure 11), show that the seasonal heating/cooling cycle of the upper part of the water column (from sea surface to 60 m depth) seems to be properly reproduced by the model. The sinking of the isotherm of 14 ºC, which indicates the beginning of the water column stratification (thermocline), starts in late April in both buoy data and model results. This isotherm is located around 50-60 m depth in the buoy data and slightly deeper in the model. The stratification period lasts until middle October. At deeper levels, some differences are observed concerning the depth of the 12ºC isotherm, located in the observations at around 200 m depth, and above 150 m depth in the model.

The time-averaged vertical profiles of RMS and MRD errors between ROMS model temperature and observations for 2007 at the Donostia buoy are shown

in figure 12. At 10 m depth, RMS error is 0.8 ºC, and increases until 1.3 ºC at a depth of 30 m. Maximum values of error around the thermocline are expected due to the differences in the thermocline depth and the strong gradients that characterize this part of the water column. The errors decrease progressively below 30 m, until 100 m depth, where the value is 0.6-0.7 ºC. From here to 200 m depth, the RMS error increases slightly to be 1 ºC. MRD error gives an estimate of the global tendency of the model to overestimate (positive MRD values) or underestimate (negative MRD values) the observations. As it can observe, the model tends to underestimate the temperature in the water column.

Plots of hourly observations of sea surface currents (at the Donostia and Matxitxako buoys) versus ROMS simulations, for february-march 2007, are shown in figure 13. The best linear fit is reached for the data registered by the Matxitxako buoy, with a determination coefficient, r2, of 0.8 for the U component of the current. For the V component, r2 is 0.5. At the Donostia buoy location, r2 is 0.5 and 0.1 for the U and V components, respectively. The differences between Matxitxako and Donostia buoys are due to the buoy locations. Matxitxako buoy is placed farther to the French coast, where wind and current fields are more constant in direction and less affected by the proximity of the land. However, Donostia buoy is located in a region with a high variability of the sea surface current direction. In this case, the change in the bathymetry and shoreline orientations (from E-W to N-S) and the freshwater discharges due to the presence of the Adour river result in a major variability of the coastal circulation.

CONCLUSIONS

In this contribution, the main advances of the pre-operational oceano-meteorological system developed in the framework of ITSASEUS project are shown. This system covers several spatial scales, combining field data and numerical modelling, in order to

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Figure 12. Vertical profile of Root Mean Square (RMS, ºC) and Mean Relative Difference (MRD) errors between ROMS model temperature and observations, integrated for 2007 between sea surface and 200 m depth at the Donostia buoy.

Figure 12: Vertical profile of Root Mean Square (RMS, ºC) and Mean Relative Difference (MRD) errors between ROMS model temperature and observations, integrated for 2007 between sea surface and 200 m

depth at the Donostia buoy.


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provide the best oceano-meteorological forecasts for the Basque Country region. The results obtained show the suitability of numerical models to explore the physics of the atmosphere and ocean in the Basque Country region. At present, the system is in its validation process in order to become in a fully operational system.

In the meteorological model case, some considerations are found. With strong synoptic forcing, good results are mainly dependent on the skilfulness of the mesoscale model to collect synoptic scale processes like frontal passages. With weak synoptic forcing, local characteristics, better defined in higher resolution domains, drive

atmospheric circulations like sea/land breezes. The correct implementation of the local characteristics is essential in the studied cases, due to the complex topography and the local features of the circulation in the Basque coastal area.

In the wind-wave subsystem case, at present time we can not describe wave conditions in coastal areas with enough detail. This is due to the basic assumptions considered in the WW3 model, which imply that the model should be applied on larger spatial scales and outside the surf zone. Results on significant wave height in deep water are acceptable, but less satisfactory in shallow water near coastal areas. Wave subsystem results can be as good as driving forces and

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Figure 13. Linear regression for the sea surface current (U and V components): plots of hourly observations (at the Donostia and Matxitxako buoys) versus ROMS simulations, for february-march 2007.

Figure 13: Linear regression for the sea surface current (U and V components): plots of hourly observations (at the Donostia and Matxitxako buoys)

versus ROMS simulations, for february-march 2007.


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especially as wind input, so nearly if global wind fields are of high quality in a real case forecast.

Concerning the hydrodynamic model, estimations of sea temperature at the surface layer show, in general, a good agreement (in terms of tendency) with the data provided by satellite images and offshore buoys. For the annual sea surface temperature, integrated for the Bay of Biscay, RMS errors are between 0.6 and 1.2 ºC. In the water column, the model is able to reproduce the seasonal heating/cooling cycle and stratification conditions, although some mismatches are observed in terms of absolute values and width of the mixed layer. More detail analysis of the surface momentum and heat fluxes is necessary to improve the ocean predictions at sea surface (especially near land boundaries), and its influence in the water column. In this sense, the parameterization of the vertical mixing processes in the water column plays a fundamental role. In this case, the model is using the nonlocal K-Profile Parameterization with standard values (Large et al., 1994). With respect to the currents, preliminary comparisons show the suitability of the model to represent the sea surface circulation offshore; the results of the models are less satisfactory near the French coast, where the proximity of the land strongly modifies the local wind and current fields.

ACKNOWLEDGMENTS

This study has been undertaken with the financial support from the Department of Industry, Trade and Tourism of the Basque Government (ETORTEK Program, ITSASEUS project). Authors would like to thank Department of Transport and Public Works and the Meteorology and Climatology Direction staff for the public provision of the oceano-meteorological data obtained from the Basque Country marine and terrestrial observation systems. We would also like to thank the Free Software Community and all institutions that maintain and support availability of free of charge data, models and tools for the Scientific Community.

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DEEP-SEA MACROBENTHIC DIVERSITY AND ASSEMBLAGES OF “A SELVA” (NW IBERIAN PENINSULA):

FIRST APPROACH FROM SAMPLES TAKEN ABOARD R/V SARMIENTO DE GAMBOA

ABSTRACT

The “A Selva” is a deep-sea area located in the Northwest of Galicia (43º30’N-44º15’N; 08º10’W-09º10’W) including the continental shelf and slope with bottoms containing extensive carbonated hard grounds. This area possesses a high interest for both fishing ground and commercial routes, but the biological characteristics of their bottoms have not been extensively studied yet. The inaugural campaign for the R/V Sarmiento de Gamboa was carried out in July 2008 and was focused on that area, embracing several approaches, ranging from the study of the water-column to the ecology and systematics of the

benthic fauna and the geology of those bottoms. In this report we present a first approach to the diversity and assemblages of the macrobenthic fauna. Samplings were done in 30 sites, at depths of about between 149 and 2,516 m, using a Naturalist dredge and an Agassiz trawl. Obtained animals up to 2 mm were assigned in their taxonomic groups and data were organized into matrices. Their diversity was evaluated by means of univariate measures (total abundance, number of taxa) and the most relatively abundant groups were estimated. Assemblages were determined by cluster analysis based on the Bray-Curtis coefficient. A total of 4,106 individuals belonging to 36 taxonomic groups were identified, being the most abundant Polychaeta, Ophiuroidea, Decapoda (Crustacea), Pteriomorphia (Bivalvia), Porifera, Hydrozoa, Hexacoralaria (Anthozoa) and Scaphopoda. The abundance and number of taxa showed great variations at different stations. The cluster analysis was able to separate five clusters which seem to be defined mainly by the bottom types and depth. These results allow us to evaluate the basic faunistic composition of “A Selva” and to serve as starting point for more detailed taxonomic and ecological investigations of benthic zoological groups.

(1) Departamento de Ecología y Biología Animal, Facultad de Ciencias del Mar, Campus Lagoas Marcosende,E-36310, Universidad de Vigo (Spain). Corresponding author: [email protected]

(2) Fundación CEQUA, Centro de Estudios del Cuaternario de Fuego-Patagonia y Antártica, Punta Arenas (Chile)

(3) Estación de Bioloxía Mariña da Graña, Rúa da Ribeira 1, E-15590. Universidade de Santiago de Compostela (Spain)

(4) Departamento de Zooloxía e Antropoloxía Física, Facultad de Bioloxía, Universidade de Santiago de Compostela,E-15782. Santiago de Compostela (Spain)

Key words: macrofauna, deep-sea, carbonated hard grounds, Galicia, Atlantic Ocean

CRISTIAN ALDEA(1,2), GUILLERMO DÍAZ-AGRAS(3), ÓSCAR GARCÍA-ÁLVAREZ(4), JUAN MOREIRA(3), MARCELO RODRIGUES(1), RAMIRO R. TATO(3), VICTORIANO URGORRI(3,4) & JESÚS S. TRONCOSO(1)

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CRISTIAN ALDEA, GUILLERMO DÍAZ-AGRAS, ÓSCAR GARCÍA-ÁLVAREZ, JUAN MOREIRA, MARCELO RODRIGUES, RAMIRO R. TATO,VICTORIANO URGORRI & JESÚS S. TRONCOSO

14

Figure 1. Geographic situation of the “A Selva” and sampling sites.

Figure 1: Geographic situation of the “A Selva” and sampling sites.

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DEEP-SEA MACROBENTHIC DIVERSITY AND ASSEMBLAGES OF “A SELVA” (NW IBERIAN PENINSULA):FIRST APPROACH FROM SAMPLES TAKEN ABOARD R/V SARMIENTO DE GAMBOA

INTRODUCTION In the last years, there is an ongoing interest in

the study of the benthic diversity at the deep-sea and the factors controlling that diversity (Levin and Gage, 1998). Most studies have, however, only been done at local spatial scales because, in many cases, of technical limitations (Gage, 2004). Consequently, understanding the variation of patterns of diversity and composition of assemblages at larger scales is limited by the lack of knowledge in many areas (Rex et al., 1993). The deep-sea benthic faunas of the Atlantic Ocean are among the best known (see, for example, Haedrich et al., 1975; Paterson and Lambshead, 1995; Billet et al., 2001) although many areas have been scarcely studied, including those around the Iberian Peninsula (Parapar and Moreira, 2009). In addition, the growing human pressure on the deep-sea derived from fishing and other activities calls for a better knowledge of that environment in order to develop better approaches for conservation and sustainable use of the open ocean (Probert, 1994).

The composition and distribution of benthic faunas at some areas off the continental shelf of Galicia (NW Iberian Peninsula) has been well characterized in the last decades (e.g. Tenore et al., 1982; López-Jamar and González, 1987; López-Jamar et al., 1992). By contrast, there is a lack of data about bathyal benthic assemblages at the Galician continental slope (but see Amoureux, 1972; 1974). In the last years, several projects have, however, partially contributed to fill in this gap in our knowledge; those were mostly devoted to study the effects of upwellings and biological processes (Flach and de Bruin, 1999; Flach et al., 2002; Lavaleye et al., 2002) and those of the “Prestige” oil spill on the benthic fauna (Serrano et al., 2006). In spite of that, many interesting deep-sea areas remain still poorly studied. Among those enclaves, the “A Selva” (fishery bank) is remarkable because of its location, on the way of commercial routes, its economic interest as fishing ground and its geological features, which include the presence of extensive carbonated hard grounds. This fishery bank is located in the Northwest

of Galicia (43º30’N-44º15’N; 08º10’W-09º10’W), off the Ria de Ferrol, Ares e Betanzos and A Coruña, and comprises large parts of the Galician continental shelf and slope. Previous data from samples collected during fishing activities suggest that this is a particular rich environment in terms of benthic fauna (Urgorri, personal observations). In this context, the inaugural campaign for the R/V Sarmiento de Gamboa was carried out in July 2008 and was focused on that area, embracing several approaches, ranging from the study of the water-column to the ecology and systematics of the benthic fauna and the geological characteristics of the bottom. In this paper, we present a first approach at a higher taxonomic level to the diversity and distribution of the assemblages of the macrobenthic fauna at the “A Selva”.


Sampling was done onboard the R/V Sarmiento de Gamboa in 30 sites across the “A Selva” (Table 1; Fig. 1), covering the continental shelf and slope at depths of about between 149 and 2,516 m. Sampling was done using a Naturalist dredge (Fig. 1A) and an Agassiz trawl (Fig. 1B), similar to the ones described by Parapar and Moreira (2009). Trawling was carried out for 30 minutes at a speed of 1.5 knots after the gear reached the bottom. Samples obtained (Fig. 1C) were sieved (Fig. 1D), fixed with buffered formalin and preserved in 70% ethanol. Animals retained in sieves of ≥2 mm were sorted onboard and then assigned in their zoological groups and quantified for each site.

Data were organized into matrices and faunistic richness and structure was evaluated by means of univariate measures (total abundance and number of taxa) and the most abundant groups that presented up to 5% of the total individuals were estimated. Assemblages were determined through non-parametric multivariate techniques. The Bray-Curtis similarity coefficient was applied to the abundance matrix previously transforming the data by the fourth root. The classification of sampling stations was determined by means of cluster analysis.

172


RESULTS Eight main types of bottoms were found in the

studied area: sandy mud (Fig. 3A), muddy sand (Fig. 3B), alive and dead corals across sandy patches (Fig. 3C), stones (Fig. 3D), corals and limestone (Fig. 3E), nodules (Fig. 3F), carbonated hard grounds (Fig. 3G), and mixed hard bottoms (Fig. 3H).

A total of 4,106 individuals belonging to 36 major taxonomic groups were identified. The most abundant groups were, in decreasing order: Polychaeta, Ophiuroidea, Decapoda (Crustacea), Pteriomorphia (Bivalvia), Porifera, Hydrozoa, Hexacoralaria (Anthozoa) and Scaphopoda (Fig. 4).

Generally, polychaetes were found in great number in all bottom types. Scaphopods and decapod crustaceans were found mostly in soft bottoms; pteriomorph bivalves and hexacorals were abundant both in soft and hard bottoms (Fig. 3C). On the other hand, some taxa were more abundant in hard substrata rather than in other bottoms, such as ophiuroids (sometimes appearing in larger aggregations), poriferans and hydrozoans (Fig. 3E).

The number of taxa and abundance showed great variations across stations (Fig. 5). The maximum value of number of taxa was found in the station 15-2b (22 taxa) while the minimum value was

15

Figure 2. Naturalist dredge (A), and Agassiz trawl (B) used for the sampling, an

example of bulk of sample of coral bottoms (C), and the sorting (D).

Figure 2: Naturalist dredge (A), and Agassiz trawl (B) used for the sampling, an example of bulk of sample of coral bottoms (C), and the sorting (D).

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16

Figure 3. Bottom types of the “A Selva”. Sandy mud (A), muddy sand (B), live and

dead corals with sandy patches (C), Stones (D), Coral and limestone (E), Nodules (F),

carbonated hard grounds (G), and hard bottoms mixed (H). Arrows showing the

conspicuous fauna for some bottoms.

Figure 3: Bottom types of the “A Selva”. Sandy mud (A), muddy sand (B), live and dead corals with sandy patches (C), Stones (D), Coral and limestone (E),

Nodules (F), carbonated hard grounds (G), and hard bottoms mixed (H). Arrows showing the conspicuous fauna for some bottoms.

174


17

Figure 4. Ranking of the stations according the m

ost abundant groups.

Figure 4: Ranking of the stations according the most abundant groups.

18

Figure 5. Num

ber of taxa (T) and total abundance (N) in each station.

Figure 5: Number of taxa (T) and total abundance (N) in each station.

175


recorded at station 7-4 (one taxon). The highest number of individuals was recorded at station 13 (481 individuals) because of the high abundance of hexacorals; while the lowest abundance was recorded at station 7-4 where only one Asteroidea was found. The cluster analysis was able to separate five clusters (Fig. 6) determined as statistically significant by profile test SIMPROF (P<0.05), which seem to be defined mainly by the bottom types and depth. The larger cluster (Fig. 7) was composed by a range of stations representing all type of sediments –including the carbonated hard grounds– and comprised the major part of the “A Selva”.

DISCUSSION

The present paper is the first to report on “A Selva” deep-sea benthic assemblages. The preliminary found results suggest that this area supports a wide diversity of many benthic invertebrate taxa, ranging from sponges and corals to echinoderms. However, the true faunal diversity could only be assessed after

studying in detail the fauna retained in meshes smaller to 2 mm. Here, in order to provide a first approach to the faunal characteristics of the area, taxonomic resolution used was at that of the level of higher taxa (from phylum down to class or order, according to the taxa); this was also due to the limited knowledge on many deep-sea zoological groups which will need further careful taxonomic studies. Undoubtedly, forthcoming taxonomic studies will reveal a greater benthic diversity to the species level. In fact, several taxa have been described as new to science from nearby deep-sea areas in recent years (see Moreira and Parapar, 2007a, 2007b) or are in the process of being formally described (Zamarro, personal communication). This fact points out again the necessity of further taxonomic studies in the deep-sea environment, even in European seas whose benthic faunas are supposed to be better known than those of other parts of the world.

On the other hand, there is a variety of soft and hard bottoms across “A Selva” which provides with

19

Figure 6. Macrobenthic assem

blages in the study area determined by cluster analysis

based on

the B

ray–Curtis

coefficient. The

clusters are

indicated according

the

SIMPR

OF test indicating the predom

inant bottom type.

Figure 6: Macrobenthic assemblages in the study area determined by cluster analysis based on the Bray–Curtis coefficient. The clusters are indicated

according the SIMPROF test indicating the predominant bottom type.

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many different habitats for both epi- and infaunal taxa. According to multivariate analyses, faunal composition seems to be related to the nature of the substratum. For example, hard bottoms are characterised by the presence of sessile epibenthic taxa, such as corals, hydrozoans and sponges, while sedimentary substrata were dominated by scaphopods and polychaetes. These results agree with those of previous work which point out the existence of different physical environments and substrata from the continental shelf to the abyssal domain in the Iberian Margin, which, in turn,

support different faunal assemblages (Flach and de Bruin, 1999; Flach et al., 2002; Parapar and Moreira, 2009). The presence of heterogenous substrata at the deep-sea has been related with greater benthic diversity (Gray, 1974; Etter and Grassle, 1992). However, the characteristics of the substrata at the continental slope of the Iberian Margin seem to be utterly related to the hydrodynamic regime, which is characterised by high current velocities (Flach and de Bruin, 1999); similar situations have been reported elsewhere (see Blake and Grassle, 1994). Thus, high hydrodynamism derived, for example,

20

Figure 7. Distribution of assemblages derived from the cluster analysis indicating the

predominant bottom types.

Figure 7: Distribution of assemblages derived from the cluster analysis indicating the predominant bottom types.

177


Table 1: Location, depth and bottom type from the survey stations. DRN, Naturalist dredge; AT, Agassiz trawl

178


from circulation of water masses does not allow the deposition of any substantial amount of fine sedimentary particles resulting in bottoms composed by stones and similar hard substrata. In our case, this fact is also suggested by the external appearance of stones and carbonated structures, which are devoid of mud and covered both above and below by sessile macrofauna.

Among the different substrata present in the “A Selva”, carbonated hard grounds are remarkable because of the peculiar fauna they support. These grounds are located between the deeper parts of the continental shelf and the upper continental slope (300-900 m depth); those are composed by structures similar to nodules, of sizes ranging from a few cm to 60-70 cm in length, with an irregular surface characterised by the presence of holes, cracks and crevices, this way providing a number of microhabitats for the fauna. Preliminary results and observations in situ of these structures at the time of sampling show that those are colonised by a rich epifaunal assemblage, including sponges, cnidarians, sessile polychaetes and bivalves, brachiopods and ascidians, as well as by mobile polychaetes such as polynoids, phyllodocids and hesionids. In fact, the polychaete assemblage is similar to that inhabiting stones and corals at the continental slope of the Golfo Ártabro reported by Moreira and Parapar (2008) and Parapar and Moreira (2009). In addition, monoplacophorans have recently been collected from similar substrata in nearby areas (Urgorri, unpublished results) and are likely to appear in our samples when finer fractions of samples are sorted.

In conclusion, these results allow us to evaluate preliminarily the basic faunistic composition of “A Selva” and to serve as starting point for more detailed taxonomic and ecological investigations of its benthic diversity. Because this area is also an important fishing ground, these results will help in the management and conservation of this important enclave and to assess the scope of impact of trawling and other disturbances resulting from fishing activities (Probert, 1999).

ACKNOWLEDGMENTS

We would like to thank our colleagues who have been supportive in collecting the samples used in this study, as well as the officers and crews of R/V Sarmiento de Gamboa for his help. Also we thank two anonymous referees and Cristina Vertan for improving the English. The “A Selva” oceanographic expedition was carried out under the auspices of the Autonomic Government of Galicia (Dirección Xeral de I+D+i, Consellería de Innovación e Industria, Xunta de Galicia).

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