Pacific Science (1974), Vol. 28, No.3, p. 247-255Printed in Great Britain

Reef Corals of Fanning Island I

J. E. MARAGOS2

ABSTRACT: Recent surveys indicate that the diversity of reef corals at FanningIsland is greater than previously estimated. Most of the approximately 70 speciesbelonging to 32 genera and subgenera typically are found in one of three environ­ments. A turbid lagoon fauna has high abundance but lower diversity of pre­dominantly branching forms. The clear lagoon coral fauna has both high abundanceand diversity of predominantly massive and encrusting corals. The greatestnumber of species and forms of corals are found on the leeward ocean reefs. Theabundance and diversity of corals along windward reef slopes are controlled bywave action. Although Fanning and others of the Line Islands presently containthe greatest generic diversity of corals of any island group in the central andeastern Pacific, diversity is considerably less than that reported for island groupsin the western Pacific. Geographic isolation appears to be the most plausible factoraccounting for reduced coral diversity in the Line Islands. The reef coral fauna ismore nearly comparable with that of island groups south and west than to those ofthe north (Hawaii).

PREVIOUS STUDIES of reef-building corals atFanning Island (3 0 N, 1590 W, Line Islands)have been confined to collections and surveys ofspecific areas within the lagoon. :A tentativereport on the species list of corals collectedfrom Fanning Lagoon (Maragos, Roy, andSmith 1970) suggests that Fanning Island, andperhaps the Line Islands as a group, include agreater variety of reef corals than previouslythought (Wells 1954). Other studies indicatethat flourishing coral communities exist withinthe lagoon (Roy and Smith 1971). A secondexpedition to Fanning in July and August 1972provides the basis for a description of thedistribution and abundance of reef corals froma broad spectrum of both lagoon and oceanreefs. Information gathered during the assem­blage of a large coral collection from the atollis used to compare the relationships of theFanning fauna with those of coral faunas ofother Pacific islands.

J Hawaii Institute of Marine Biology contributionno. 434. Hawaii Institute of Geophysics contributionno. 604. Coral Reef Management and Research con­tribution no. 3. This study was supported by NationalScience Foundation grant F331-0-260-3230 and NFS SeaGrant04-3-158-29.Manuscriptreceived 1September1973.

2 University of Hawaii, Department of Oceanog­raphy, Honolulu, Hawaii 96822.

METHODS

Fifty reef sites were visited by a team ofscientists working from a small skiff; locationsof these sites are found in Chave and Eckert(fig. 1, this issue). At each site divers gatheredinformation on various reef organisms, in­cluding the corals. Notes on circulation, depth,substrate composition, relief, and other physicalproperties were also recorded. A referencecollection of reef corals was assembled. Skele­tons were cleaned in dilute hypochlorite(Clorox) and shipped to Hawaii for analysis.The corals were identified by comparison withreference collections of the author; the BerniceP. Bishop Museum, Honolulu, Hawaii; and theHawaii Institute of Marine Biology, Universityof Hawaii, Honolulu, Hawaii. John W. Wells ofCornell University generously identified someof the corals. Useful references consulted in­clude those of Vaughan 1918; Vaughan andWells 1943; Crossland 1952; Wells 1954, 1956;and Wijsman-Best 1972. A species list of thecorals including their relative abundance atFanning is given in Table 1.

247

248 PACIFIC SCIENCE, Volume 28, July 1974

TABLE 1

SPECIES LIST OF STONY CORALS FROM FANNING ISLAND

DISTRIBUTION FREQUENCY

CLEAR TURBIDSPECIES OCEAN LAGOON LAGOON RARE AVERAGE ABUNDANT

Acropora sp. cf. A. abrotanoides (Lam.) x x xAcropora corymbosa (Lam.)t x xAcropora cymbicyathus (Brook) x xAcropora sp. cf. A. de/icatula (Brook) x x xAcropora formosa (Dana) x xAcropora humilis (Dana) x xAcropora nasuta (Dana) x x xAcropora polymorpha (Brook) x xAcropora reticulata (Brook) x x xAcropora syringodes (Brook) x x xAcropora vaughani Wells x x xAgaricie!!a ponderosa (Gardiner) x xAlveopora verri!!iana Dana x xAstreopora sp. cf. A. gracilis Bernard x xAstreopora listeri Bernard x x xAstreopora myriophthalma (Lam.) x x xAstreopora oce!!ata Bernard x x xCoscinaraea ostreaeformis Van der Horst x xCulicia ste!!ata+ x xDistichopora violacea (Pallas):j:§ x xEchinophy!!ia aspera (Ellis & Solander) x x xFavia pa!!ida (Dana) x xFavia speciosa (Dana) x x x xFavia ste!!igera (Dana) x x x xFavites abdita (Ell. & Sol.) x x xFavites halicora (Ehr.)t x xFungia fungites (Linn.) x x xFungia (Pleuractis) sClltaria Lamarck x x x xFungia (Verri!!ofungia) concinna Verrill x xHerpolitha limax (Esper) x xHydnophora microconos (Lam.) x x xHydnophora rigida (Dana) x x xLeptastrea purpurea Dana x x xLeptastrea transversa (Klz.) x xLeptoria phrygia (Ell. & Sol.) x xLeptoseris mycetoseroides Wells x xLobophy!!ia costata (Dana) x x xMerulina ampliata (Ell. & Sol.) x x x xMi!!epora platyphy!!a Hemp. & Ehr.§ x x xMontipora elschneri Vaughan x xMontipora hoffmeisteri Wells x x xMontipora patula Verrill x xMontipora socialis Bernard x x xMontipora tuberculosa (Lam.) x x xMontipora verri!!i Vaughan x x x xMontipora verrtlcosa (Lam.) x x xPachyseris speciosa (Dana) x xParahalomitra robusta (Quelch) x xPavona clavus (Dana) x x xPavona divaricata Lam. x xP avona gigantea Verrill x x xP avona varians Verrill x x xPavona (Pseudocolu7tl11astraea) po!!icata Wells x xPlatygyra Imlle/lina (Ehr.) x x x x

Reef Corals of Fanning Island-MARAGOS

TABLE 1 (,·ont.)

249

DISTRIBUTION FREQUENCY

CLEAR TURBIDSPECIES OCEAN LAGOON LAGOON RARE AVERAGE ABUNDANT

PlatygJ1ra sinensis (M. Ed. & H.) x x xPlesiastrea sp. d. P. cllrta (Dana) x xPlesiastrea versipora (Lam.) x x xPocillopora damicornis (Linnaeus) x x x xPocillopora eydollxi M. Ed. & H. x xPocillopora meandrina var. nobilis Verrill x x xPocillopora molokensis Vaughan x xPocil/opora pallcistellata Quelch x xPocillopora verrllcosa (Ell. & Sol.) x xPorites lobata Dana x x xPorites IlIlea M. Ed. & H. x xPorites pllkoensis Vaughan x xPorites (Synaraea) vallghani Crossland x xPsammocora contigila (Esper.) x xPsammocora verrilli Vaughan x xPsammocora (Plesioseris) profllndacella x x x

GardinerStylaster elegans Verrill:j:§ x xStylophora mordax (Dana) x x x xStylophora pistillata (Esper) x xTubastraea coccinea Lesson:j: x x xTllrbinaria velllta Bernard* x x

Total Number 48 46 27Number of Unique Forms 21 9 5

* Christmas Atoll only.t Vaughan (1918) only.:j: Ahermatypes.§ Hydrozoan corals.

RESULTSThe Lagoon

Fanning Lagoon is a shallow, oval-shapedbasin of approximately 116.6 km2 with a singledeep pass at English Harbor on the westthrough which 95 percent of lagoon/oceanwater exchange occurs (Gallagher et al. 1971;Stroup and Meyers, this issue). Two shallowpasses, Rapa on the southeast, and North Passon the north, are shallow flats less than 1 meterin depth. Because of the restricted movement ofwater into and out of the lagoon, the physicaland chemical character of the lagoon water isnoticeably different from that of the oceanicwaters (Smith and Pesret, this issue). The lagoonbasin is divisible into two areas on the basis ofwater clarity: a clear water sector in the vicinityof the deep pass (English Harbor) and turbidwater sectors where the water clarity is reducedby the presence of suspended calcium carbonate

(Smith and Pesret, this issue) in the north andsouth basins of the lagoon.

The turbid lagoon is characterized by long,narrow, ribbonlike reefs that form networksacross the sandy bottom and enclose a numberof basins or ponds (Roy and Smith 1971,Gordon and Schiesser 1970). The tops of theline reefs are within 1 meter of the sea surface.The walls have gentle to steep slopes. Coralcover is relatively high considering the amountof sediment cover and sediment in suspension,and average coral cover in one northern pondwas estimated to be over 30 percent (Roy andSmith 1971). Lagoon ponds adjacent to NorthPass showed higher average coral cover; areasaway from the passes showed lower overallcover. Corals grow profusely on the tops andsides of most of the line reefs. Where sand iscommon, especially on the leeward side of thewider reefs, coral abundance is locally reduced.Corals also grow abundantly on numerous

250

patches and pinnacles on the floor of the ponds.The turbid lagoon in the vicinity of Rapa Passis shallow and essentially a large sandy reef flat.Numerous microatoll formations of Porites luteaoccur on this flat.

Where the line reefs and pinnacles reach thesea surface, the reefs are dominated by thebranching corals Srylophora mordax and Acroporadelicatula. Pocillopora damicornis, Acropora for­mosa, Plarygyra lame/lina, and Montipora verrucosaare also common. On the sides of the reefs andpinnacles several varieties of Acropora usuallyoccur, and Astreopora, Plarygyra, and Favia arecommon. Merulina, Favites, Pavona, and Psam­mocora are less frequently seen growing underledges. The unattached solitary coral Fungia(P.) scutaria was also seen on some shallow sandflats in the turbid lagoon. Most of the coralsare attached to hard substrate. Except undercoral ledges average colony size was large.

A preponderance of branching forms occurin the turbid lagoon as compared with otherlagoon environments at Fanning (Roy andSmith 1971). The prevalence of branchingforms may imply these forms better resistsedimentation (Roy and Smith 1971) or that theycan outcompete other forms for suitablesubstrates.

Despite the relatively high coral cover, thenumber of corals characterizing the turbidlagoon environment is few relative to that ofother environments at Fanning (Table 1). Onlyfive species of 71 were restricted to the turbidlagoon. The same common species were seenrepeatedly at nearly all of the sites surveyedwithin the turbid lagoon. Environments forreef-building corals in the turbid lagoon appearto be favorable for only a small number of coralswhich may compete among one another for thelimited amount of hard substrate available forcoral settlement.

The middle of the lagoon adjacent to the passat English Harbor comprises the clear lagoon(Chave and Eckert, fig. 1, this issue); this area ischaracterized by greater depths than occur inthe turbid sectors of the lagoon and by clearerwater and swifter currents. The line reef net­work of the turbid lagoon is replaced byconcentrations of coral pinnacles of variablesize. The larger of these formations are widelyspaced and do not restrict exchange of water.

PACIFIC SCIENCE, Volume 28, July 1974

Rippled sand dominates the substrates betweenthe patches. These observations indicate thatboth circulation and exchange of lagoon wateroccur more readily in the clear lagoon than inthe turbid lagoon. The reef coral fauna is morediverse and more abundant than that of theturbid lagoon. Coral coverage is approximately60 percent in one area of the clear lagoon, andmassive and encrusting types of corals pre­dominate (Roy and Smith 1971). The averagesize of individual colonies appears to be smallerthan in the turbid lagoon. Several species ofencrusting Montipora usually dominate the hardsubstrate and Plarygyra, Favia, Porites lobata,Pocillopora meandrina, Hydnophora, Leptastrea,Pavona, Astreopora, Lobop!?Jllia, and Plesiasteaare also common. Vertical zonation of coralswas not apparent. Most of the species of theclear lagoon were also recorded within eitherthe turbid lagoon or oceanic reef environments.These observations also suggest that clearlagoon habitats for corals are intermediatebetween oceanic and turbid lagoon environ­ments.

Seaward Reefs

Tradewinds and surf are predominately fromthe southeast at Fanning, and the character ofthe windward ocean reefs is grossly differentfrom that of the leeward ocean reefs. Rubble orshingle ramparts are found both offshore onreef flats and onshore along much of the sea­ward coastline of Fanning. These beaches mayhave been formed during times when waveaction and storm activity were severe (Gal­lagher 1970). Some of the offshore rampartsenclose old reef flat, forming shallow moatscharacterized by moderate sediment and cur­rents; water in these moats is oceanic. Coralcomposition within these moats is not unlikethat of the clear lagoon. Although the faunavaries from location to location, Acropora,Pocillopora, Psammocora, Hydnophora, and Faviaare consistently present. Solitary corals of thegenus Fungia are occasionally found. Theabundance and average colony size are usuallysmall, although coral development in the largemoat near English Harbor (Danger PointTidepool of Chave and Eckert, this issue) islocally flourishing.

Reef Corals of Fanning Island-MARAGos

On reef flats lacking offshore ramparts, coraldevelopment is usually poor. Calcareous orfleshy benthic algae apparently outcompetecorals on these flats. Coral cover is also lowwhere moving sand is common, especially alongsome leeward shores. Wide and shallow reefflats occur at Greig Point (Chave and Eckert,fig. 1, this issue) and other localities along theleeward coast. Elsewhere the reef flats arepoorly developed and are deeper. Along muchof the windward coast (east and southeast) thereef flats are almost nonexistent. Because of theabsence of an outer reef edge, waves break nearshore. Except for a few hardy forms ofLeptastrea, Ffydnophora, and Pocillopora, reefcorals are nearly absent in these environments.It has been suggested that Fanning Island istilting so that the windward (eastern) islandsare becoming submerged relative to landareas along the western rim (Roy and Smith1971). This hypothesis may also explain, atleast in part, the poor reef flat developmentalong windward coasts.

The deep windward reef slopes were notsurveyed in great detail because of logisticalproblems. The upper slopes appear to bedominated by calcareous red algae (Porolithon),and loose shingle is also common within theupper few meters. The groove and spursystem is well developed at some locations butis apparently absent or destroyed in others,such as offshore from North Pass. Reef coralsare absent from the upper several meters of thewindward slopes. Beginning at a depth of6 meters, a broad shelf extends seaward forseveral hundred meters. Sediment is absent andreef corals are common, especially encrustingMillepora, tabulate Acropora, and branchingPocillopora. At depths of about 15 meters, coralcoverage may be 50 percent or greater. Themost common corals include Acropora reticulata,Millepora pla0'phylla, S0'lophora mordax, Ffydno­phora microconos, Pocillopora meandrina, and Faviaspeciosa. Between the coral patches are largefields of broken coral fragments and rubble.Reef slope environments may be periodicallydevastated by large waves and moving rubble.Coral coverage is poor above depths of 10meters and the fauna is not so diverse as it is offleeward ocean reefs. None of the coralsappeared to be unique to windward reefs.

251

These observations suggest that the characterof shallow windward reef slopes is stronglycontrolled by wave action and associatedfactors.

In contrast to the windward reef slopes, theleeward ocean reef slopes harbor greaterabundance and diversity of reef corals. Shingleand calcareous red algae are common within theupper few meters as on the windward reefslopes, but below these depths coral dominatesall substrates to depths of 35 meters or more.Average coral abundance for the reef slopenorth of English Harbor Passage was about70 percent. Corals (Maragos, this issue) andreef fish (Chave and Eckert, this issue) werefound to be strongly zoned with respect todepth. The most common corals along leewardocean reefs from shallow to progressivelygre::tter depths include Mil/epora pla0'p!?Jlla,Acropora reticulata, Pocillopora meandrina, 50'10­phora mordax, Favia stelligera, Pavona varians,Lobop!?Jllia costata, Sarcophyton sp. (a soft coral),Echinop!?Jllia aspera, and Leptastrea purpurea.Several varieties of solitary unattached fungiidcorals were also noted at moderate depths. Thebottom of the coral reef slope communityterminates at a sand talus which appears toextend to great depths. The great number ofcoral species and the many unique speciesfound along leeward ocean reefs suggest thathabitat diversity is greatest in this area and thatenvironmental conditions are favorable.

DISCUSSION

The coral fauna at Fanning Island can beconveniently classified into turbid lagoon, clearlagoon, and ocean components (Table 1). Thedegree of circulation, wave action, depth, andsediment cover appear to determine whichforms predominate in each of these environ­ments.

The Fanning Island reef coral fauna is muchmore diverse than previously reported (Wells1954, Stehli and Wells 1971). Recent investi­gations (including Maragos, Roy, and Smith1970) have nearly tripled both the number ofspecies and genera reported from an earlierstudy at Fanning (Vaughan 1918). Intensiveand more efficient collection by SCUBA

252 PACIFIC SCIENCE, Volume 28, July 1974

TABLE 2

LIST OF SUBGENERA AND GENERA OFREEF-BUILDING CORALS REPORTED IN THE

LINE ISLANDS

NOTE: Names in parentheses indicate subgenera. Datataken from Wells, unpublished; Wells 1954; Maragos,Roy, and Smith 1970; and the present study.

* Not reported at Fanning Island.

probably accounts for most of the discrepancy,as does sampling in the lagoon which was notpreviously sampled (Vaughan 1918). Thespecies list of 71 hermatypes should be con­sidered conservative especially for coralsbelonging to the genera Montipora and Acropora.Growth form variation noted among individualspecies of especially these genera during thisstudy has led to some revision of the earlier list(Maragos, Roy, and Smith 1970) compiledwithout the advantage of reef observations.

Because of the problems associated withgrowth form variation in corals, systematictreatment at the species level is less reliable thanat higher taxonomic levels. For this reason,recent studies of the zoogeography of reefcorals are based on the distribution of thesubgenera and genera (Wells 1954; Stehli andWells 1971 ; Woodhead and Weber 1969; andWeber 1973a, b).

The new records from Fanning Islandincrease the number of genera and subgenera ofreef corals in the Line Islands from 23 to 35(Table 2). These results reemphasize the im­portance of Wells' (1954) discussion of theproblems of comparing areas where coralsampling effort is variable. The Line Islandswere thought to be an area well sampled forreef corals (Stehli and Wells 1971), even before

the recent expeditions to Fanning. No doubtfuture intensified collection with SCUBA maythus alter the generic coral diversities of anyPacific island group.

The 35 subgenera and genera of reef coralsin the Line Islands is the highest numberpresently reported for any island group to theeast of Samoa. However, comprehensivecollections have not been assembled from thePhoenix Islands and other central Pacificislands, and future collections may well alter thepresent pattern. Nevertheless, coral diversity inthe Line Islands is not so great as that reportedfor Samoa, the Marshall Islands, or other islandgroups of the western Pacific (Wells 1954,Stehli and Wells 1971). The absence of Helio­pora, Seriatopora, Symphyllia, and many othercommon western Pacific corals supports thisargument. Stehli and Wells (1971) suggestedthat the evolution of reef coral genera isoccurring more rapidly on the western sides ofthe Pacific; these areas also show the greatestgeneric diversity.

Mean annual seawater temperatures arenoticeably higher on the western edge than inthe central or eastern Pacific (Stehli and Wells1971). Greatest coral diversities occur whereannual seawater temperatures are greater than80° F (Stehli and Wells 1971). Because the LineIslands are located on the equator and are wellwithin the 80° F isotherm, temperature per sedoes not appear to explain the lower diversityof corals, at least under present climatologicalconditions.

The greater number of island groups in thewestern Pacific may have promoted greaterdiversification of corals there because of greaterhabitat space and types (Stehli and Wells 1971).The closer proximity of island groups to oneanother in this area of the Pacific may tend toreduce geographic isolation and promote homo­geneity, and, therefore, greater diversity ofcorals at each island group. The main LineIslands (Washington, Palmyra, Fanning, andChristmas) are about 1,600 km south, southeast,and northeast of Hawaii, Johnston Island, andthe Phoenix Islands, respectively. The SocietyIslands, Marquesas, and Tuamotus lie 1,800 to2,300 km south and southeast of the LineIslands. The Cook Islands lie 1,600 km to thesouthwest. Lack of sufficient island habitat

NEW RECORDS

Agaricie!laAlveoporaCoscinaraeaEehinophylliaFungiaLeptoriaLeptoserisMilleporaPachyseris(Pseudocolumnastraea)(Synaraea)(Verrillofungia)

ParahalomitraPavonaPlatyJ!)raP lesiastrea(Plesioseris)(Pleuraetis)PoeilloporaPoritesPsammoeoraStylophoraTurbinaria*

AcroporaAstreoporaCyphastrea*FaviaFavitesGoniastrea*Herpo/ithaHydnophoraLeptastreaLobophylliaMerulinaMontipora

EXISTING RECORDS

Reef Corals of Fanning Island-MARAGos 253

17

TABLE 3

SUBGENERA AND GENERA OF REEF CORALSIN THE CENTRAL AND EASTERN PACIFIC

NOTE: 1, Hawaiian Islands; 2, Cook Islands; 3,Society Islands; 4, Marquesas Islands; 5, TuamotuIslands; 6, Line Islands; 7, Panama; 8, GalapagosIslands; 9, Phoenix Islands. Names in parenthesesindicate subgenera. Data taken from Wells, unpublished;Wells 1954; Stoddart and Pillai 1972; and the presentstudy.

common in Hawaii. Even more striking is theabsence of Porites compressa or any branchingequivalent of Porites at Fanning; branchingPorites is perhaps the most common Hawaiianform (Maragos 1972). An analogous branchingform, Stylophora mordax, dominates habitats inFanning Lagoon which might otherwise be quitefavorable for branching Porites. Isolation mayalso explain discrepancies in occurrence ofgenera among the individual atolls of the LineIslands. Although Cyphastrea, Turbinaria, andGoniastrea have been reported from Christmasor other atolls, I did not find them at Fanning,even after an extensive search.

The islands of the central and eastern Pacificcollectively do not show generic coral diversityas high as that exhibited by individual islandgroups in the central Pacific to the west ofSamoa. Thus, not only is isolation betweenarchipelagoes of the central Pacific possible,but isolation of the whole area from the westernPacific is probable.

It has been suggested (Vaughan 1907, andothers) that the planula larval stage of coralsdoes not survive long enough to facilitate coraldispersal between island groups separated bywide distances. Although Harrigan (1972) hasshown that Pocillopora larvae can remain viableand settle after several months, other studies(Maragos 1972) suggest that Pocillipora may beadapted for high dispersal associated withbetter survival in certain reef habitats. Othercorals may not produce nearly as many larvaeor may not produce planulae that will surviveas long as those of Pocillopora.

Central Pacific island groups are isolatedfrom the western Pacific in other ways. Pre­vailing winds and currents tend to move east towest. Since coral planulae probably cannotswim against currents, corals in the central Pacificare essentially "upstream" from the westernPacific, which is the center of evolution of reefcorals in the Pacific (Stehli and Wells 1971).Thus, a combination of distance and currentpatterns may account for isolation, resulting inlower coral diversity of areas in the central andeastern Pacific. The greater similarity of theLine Island coral fauna to that of MarshallIslands suggests that the former fauna wasderived recently from areas to the west.

The dissimilarity and low diversity of the

HPS 28

Millepora (2, 3, 4, 5, 6, 7, 9)Montipora (1, 2, 3, 4, 5, 6, 9)Mycedilll71 (3)Oxypora (3)Pachyseris (3, 6)Parahalomitra (3, 6)Pavona (1, 2, 3, 5, 6, 7, 8, 9)P1atyf!)ra (2, 3, 5, 6, 9)Pleiiastrea (2, 3, 4, 5, 6)(P1esioseris) (2, 3, 6)(Pleuractis) (1, 2, 3, 4, 5, 6)Pocillopora (all)Podabacia (9)(Polyastea) (3, 7)PoriteJ (all)Psal71l71ocora (all)(Pseudocollll71nastraea) (1, 3,

5,6)(Stephanaria) (1, 7)Stylocoeniella (2, 3)Stylophora (3, 5, 6)(Synaraea) (1, 3, 4, 6)TlIrbinaria (2, 3, 6)(Verri/fojllngia) (2, 3, 4, 5, 6)

Acanthaitrea (2, 3, 5)Acropora (2, 3, 5, 6, 9)Agaricie/fa (3, 6)Alveopora (1, 5, 6)Astreopora (3, 5, 6, 9)Coscinaraea (1, 5, 6)Cycloseris (1, 3, 7, 8)Cyphastrea (1,2,3,5,6,9)(Danajllngia) (3, 9)Echinophyllia (3, 6, 9)Echinopora (2, 9)Favia (2, 3, 5, 6)Favites (2, 3, 5, 6)(FlIngia) (3, 4, 5, 6)Galaxea (2)Goniastrea (2, 9)Halol71itra (3, 5, 9)Herpolitha (2, 3, 5, 6, 9)Hydnophora (2, 6, 9)Leptastrea (1, 2, 3, 5, 6, 9)Leptoria (2, 6)Leptoseris (1, 3, 5, 6, 7)Lobophy/fia (2, 3, 5, 6, 9)Merulina (6)

space in the vicinity of the Line Islands couldthus be one factor in limiting coral diversity.

Geographic isolation appears to be an im­portant factor in explaining the relatively poorcoral diversity of the central Pacific. Althoughno one island area in the central Pacific ischaracterized by more than 35 genera or sub­genera of corals (Table 3), collectively nearly50 genera and subgenera are reported from thewhole of the central Pacific. If fairly completecollection from these areas is assumed, thefigures suggest some isolation between indivi­dual island groups.

The Hawaiian Islands are well sampled andform the island chain closest to the Line Islands.However, a markedly different coral fauna isfound in Hawaii and generic diversity is low(14). The taxa (Stephanaria) and Cycloseris areapparently absent in the Line Islands although

254

Hawaiian coral fauna suggest the island groupis more isolated from the western Pacific thanare t.ne Line Islands. Kay (1971) came to similarconchisions regarding the shallow watermolluscan fauna of Fanning. Dora Banner andAlbert Banner (personal communication) havealso noted a lower number of species of alpheidshrimps occurring in Hawaii as compared tothat of island groups to the west of Hawaii.This pattern may characterize the distributionof other reef organisms as well.

ACKNOWLEDGMENTS

I would like to thank Edith Chave and DaveEckert for their assistance and cooperationduring the diving surveys. I would also like tothank Keith Chave and Alison Kay for theirsupport and interest. John Wells identifiedmany of the corals. The Hawaii Institute ofMarine Biology provided typing assistance.

LITERATURE CITED

CHAVE, E. H., and D. B. ECKERT. 1974.Ecological aspects of the distribution offishes at Fanning Island. Pacif. Sci. 28: 297­317.

CROSSLAND, C. 1952. Madreporaria, Hydro­corallinae, Heliopora, and Tubipora. Sci. Rep.Gr. Barrier Reef Exped. 6(3): 85-257.

GALLAGHER, B. S. 1970. A note on surf atFanning Island. Pages 191-192 in K. E.Chave, principal investigator. Fanning Islandexpedition, January 1970. HIG 70-23.Hawaii Institute of Geophysics, Universityof Hawaii, Honolulu. 201 pp.

GALLAGHER, B. S., K. M. SHIMADA, F. 1.GONZALEz,JR.,and E. D. STROUP. 1971. Tidesand currents in Fanning Atoll Lagoon. Pacif.Sci. 25: 191-205.

GORDON, D. c., JR., and H. G. SCHIESSER.1970. Temperature, salinity and oxygenobservations at Fanning Island. Pages 19-21in K. E. Chave, principal investigator. Fan­ning Island expedition, January 1970. HIG70-23. Hawaii Institute of Geophysics, Uni­versity of Hawaii, Honolulu. 201 pp.

PACIFIC SCIENCE, Volume 28, July 1974

HARRIGAN, J. F. 1972. The planula larva ofPocillopora damicornis: lunar periodicity ofswarming and substratum selection behavior.Ph.D. Thesis. University of Hawaii, Hono­lulu. 303 pp.

KAY, E. A. 1971. The littoral marine molluscs ofFanning Island. Pacif. Sci. 25: 260-281.

MARAGOS, J. E. 1972. A study of the ecologyof Hawaiian reef corals. Ph.D. Thesis. Uni­versity of Hawaii, Honolulu. 292 pp.

---. 1974. Coral communities on a seawardreef slope, Fanning Island. Pacif. Sci. 28:257-273.

MARAGOS, J. E., K. J. RoY, and S. V. SMITH.1970. Corals collected at Fanning Atoll, 1968­1970. Pages 77-84 in K. E. Chave, principalinvestigator. Fanning Island expedition,January 1970. HIG 70-23. Hawaii Institute ofGeophysics, University of Hawaii, Honolulu.201 pp.

Roy, K. J., and S. V. SMITH. 1971. Sedimenta­tion and coral reef development in turbidwater: Fanning Lagoon. Pacif. Sci. 25: 234­248.

SMITH, S. V., and F. PESRET. 1974. Processes ofcarbon dioxide flux in the Fanning IslandLagoon. Pacif. Sci. 28: 225-245.

STEHLI, F. G., and]. W. WELLS. 1971. Diver­sity and age patterns in hermatypic corals.Syst. Zool. 20(2): 115-126.

STODDART, D. R., and C. S. G. PILLAI. 1972.Coral fauna of the Cook Islands. Int. Symp.Oceanogr. South Pacific, Wellington, Feb.1972: 36 (abstract).

STROUP, E. D., and G. A. MEYERS. 1974. Theflood-tide jet in Fanning Island Lagoon.Pacif. Sci. 28: 211-223.

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