Marine algal colonization at Surtsey

BY

SIGURDUR JONSSON Laboratoire de Biologic Vkgklale Marine

UniversitC clc Paris VI, Paris

and

KARL GUNNARSSON Marine Kesearcli Institute, Reykjavik

INTRODUCTION Observations on the marine algal settlement

around Surtsey have been carried out, at fairly regular intervals, since the formation of rocky shores on the island in 1964 (Jbnsson, 196G, 1967, 1968, 1970a, 1970b, 1972). T h e investiga- tions have so far been of exploratory nature ex- tending to different parts of the shore and the sub-

littoral zone depending on the accessibility and the changii~g development of the shoreline. T h e main objectives have been the identification, the order of arrival and the distribution of pioneer popula- tions. Since the beginning of the settlement in 1964 the number of invading species has been steadily increasing. In 1970, the number of species reached 46, including 1 1 species of diatoms. How-

Fig. 2. Underwater suction sampler sl~owiug the filtering compartment with o p a l lid, the inlial;~tion tube 10 the riglit and the high prcssurc air tank connectccl wit11 tlie cxhalatioli tube. (Courtesy of J6llatnles Briem.)

ever, only a lew species were ol ecological importance. In the littoral zone two belts could be recognized, an upper one of Urospora penicilli- formis, intermixed with various accompanying species, and a lower one of colollial naviculoid diatoms in a mucilaginous matrix. T h e sublittoral vegetation was dominated by Alaria esculenta populations. This situation, as compared to that known in mature algal communities of adjacent islands, indicated that the marine algal coloniza- tion of Surtsey was yet in its pioneer stage.

This paper deals with further observations on the marine algal settlement at Surtsey carried out in 1971 and 1977.

PROCEDURES O F INVESTIGATION In 197 1 the period of investigation extended

from 20 to 30 August. Studies were carried out from the field station on Surtsey. T h e shore was explored at low tide by landing parties and the sublittoral zone by divers. T h e littoral zone was surveyed all around the island exept for the south coast which was quite inaccessible. I n the sublit- toral zone 10 transects were investigated from 0-30 m depth (Fig. 1). Dives were made at 5 , 10, 20 and 30 m depth and specimens were handcol- lected into plastic pails with cross-cut lids. T h e depth was measured with a wrist gauge. T h e nature of the bottom and the general features of the algal vegetation were recorded after each dive. T h e identification of species was made on fresh material. T h e nomenclature is mainly ac- cording to Caram and J6nsson (1972). Herbarium specimens were prepared and species photo- g ~ a p h e d for later reference.

Fig. 3. A. Plocat~ziz~m cartilagilzeuln. Sterile plant from 10 111 depth east of Surtsey, July 11 1077; nat. size 6 cm. I%. L o t ~ i e ~ l l n ~ i a clavellosa. Plant from 20 m depth south of Surtsey, July 11 1977; nat. size 17 ctn.

In 1977 the field work was performed from R / V Arni Fridriksson from 9 to 11 July in a similar way as described above. During this short survey investigations were limited to 3 subtidal transects, located off the east, west and the south coasts 01 the island (Fig. 1). Due to illaccessibility only the east and the west coasts could be ex- plored by landing parties. Most of the material collected was fixed aboard the ship in 2% for-

TABLE I Vertical and llorizolltal distribution o f marine algal species found i n Surtsey waters i n 1971 and 1977.

Sublittoral 1971 1977 Littoral -

0-10 15-20 30 m E S W E S W Species

RHODOPHYCEAE Iillodochorton f i t ~ r p t ~ r e ~ ~ ~ ~ z Ploca~nium cart i laginez~~n Iilzodophyserna elegans . .

Et~tllora cristata . . . . . .

Lonientnria clnwellosa . .

Lon~enlaria orcaderzsis . .

A n t i t h a ~ n n i o ~ z f loccosf~m . .

A ~ i t i t l ~ c ~ n z ~ z i o n p l ~ ~ m t t l a . . Uelesserin sangzdi~zea . . . .

Pl~ycodrys rubens . . . . Polysi l~ho~zin urceolata . .

Porphyra u~nbilicalis . . . . Porpl~jirn nii~ziata . . . .

Conchocelis rosea . . . .

. . . . . .

X . . . .

. . x . .

X . . . .

X X . . X X X X . . X X . . . . X X X X X X x X x X . . X X X X X - . . .

. . X

X X X . . . , . .

. , . X X X X X X X X . . X X X . . . . . X

PHAEOPHYCEAE Ectocar$us silicz~losus Ectocarpz~s fascicz~latz~s Giffordia grnnz~losa . .

Gijfordin ovatn . . . . Gifforclicl recnr71nta . . Giffordin secz~rlcla . . Petalonin fascia . . . . Petalonin zosterifolia . .

Scylosiphon lo~ne~ztaritrs Ralfsin sp. . . . . . .

Desnzareslia acttleuta . .

Dcsnlnrestin ligzilata . .

Desfl~nrestia virirlis . .

Cl~orrla filit~nz . . . . Cl~orda to~ne~z tosa . . La~izinarin hyperborecz L a n ~ i ~ ~ n r i a digituta . .

Alnria escz~lenla . . . .

X X X X . . X

. . . X

. . . X X X X X X X . . , . . .

X X X . . x . .

X X X

CHLOROPHYCEAE Codioln~m gregclriz~~fa . . . . . . . . . .

. . . . . . . . Urospora penicilliforrr~is Ulo t l~r ix co~zsociatn . . . . . . . . . .

Ulo fllrix pset~tloflaccn . . . . . . .

Ulothrix sz~bflaccitla . . . . . . . . . .

Entero~?zorpl~a prolifera . . . . . . . .

E~l teromorpl~a conzpressa . . . . . . . . Ulva lactz~ca . . . . . . . . . . . . A4onostronza grewillei . . . . . . . . Acrosipho~zia spi~zescens . . . . . . . . Derbesin marina . . . . . . . . . . . .

. . . . Psetide~ztocloniz~rm submari~~unz CYANOPHYCEAE . . . . . . . . . .

malin seawater and analyzed ashore. In three RESULTS instances plants and animals in the sublittoral

1. Species survey zone were loosened from the bottom by a scraper and collected by an underwater suction sampler The species composition of the macroscopic (Fig. 2) within quadrats measuring 25 x 25 cm marine flora off Surtsey in 1971 and 1977 and (1 116 m2). This sampling process proved to be the distribution pattern of individual species are successful but was too time-consuming. summarized in Table I.

Fig. 4. A ~ ~ t z t / ~ a t ~ ~ ~ z a o n )lrt11~1~1n var. Doreale. A part of steiilc plant with glantl cclls (arlows); specimen f ~ o m 10 rn clcpth cast of bu~tscy, July 10 1077.

A total of 31 algal species were found grow- ing in the coastal waters off Surtsey in 1971 and 34 species in 1977. T h e following 18 species were found lor the first time, 8 species in 1971 and 10 in 1977:

Rlzodochorto?z p z ~ r p z ~ r e z ~ m (Lightf.) Rosenv. Two tetraspoi-ifemus specimens were found in

1971 on Desmaresfia a c ~ ~ l e a t a collected at 8 m and 20 m depth off the west coast.

Plocumiz~m cartilagi?zeu,m (L.) Dixon Some sterile specimens were found in 1977

growing at 12 nl depth on rocks off the east coast (Fig. 3A).

Rhodophysema elegans (Crn. frat. ex J. Ag.) Dixon

Patches of this species were found in 1977 at 10 m depth of'f the south coast where they grew on bare rocks. T h e specimens were 1-5 cm in diameter arid had tetraspores between sterile nemathesial filaments 011 the surface of the thallus.

Lomentaria clavellosa (Turn.) Gaill. Several plaiits of this species were found in

1977 at 10 m depth off the east coast growing on rocks amongst Hydrozoa. T h e largest speci- men measured 20 cm and bore tetraspores (Fig. 313).

Antiblzarnnion plumula (Ellis) Thur . var. Ooreale (Gobi) I(jel1m.

A few sterile specimens with typical gland cells (Fig. 4) were foullcl in 1977 growing on hap- tera of Laminnria hyperborea.

Delesseria sangzsinea (Huds.) Lamouroux One sterile specimen partly coverecl wit11

Bryozoa was found in 1971 on roclzs at 20 m clepth off the west coast. In 1977 this species was redetected at 10-30 m depth at the same locality (Fig. 5B).

Conchocelis rosea This alga which is the sporophyte in the life

history of Porphyra or Bangia .cvas found in 1977 off the east coast at 10-20 m depth growing on mussels and calcareous Polychaeta tubes. I t was sterile when collected.

Kalfsia sp. In 197 1 a small crust of the genus Ralfsia was

found growing on the shore at the west coast amongst Eclocar-pus and Petalonia. On one oc- casion Petalonia was found growing on the crust. T h e specimens were sterile.

Desmarestia acrlleata (L.) Lamouroux In 1971 one sterile specimen, 75 cm in length,

was found on rock at 20 m clepth off the west coast (Fig. 6). Another specimen found five days later in the same locality measured 60 cm.

Gijfordia sec~incla (Kiitz.) Batt. This species was first detected in 1971 in a

collection from 3-19 m depth off the SW-coast. T h e plants grew on rocks and bore ovoid pluri- locular sporangia.

Gifforclia recurvatu (ICuckuck) Cardinal This species n~hich was not previously kno~vn

from Iceland g-relv up together with Giffordia ovata and Giffordia granz~losa in stock culture of Derbesia marina collected in 1977 at 10 m depth off the east coast. Our specimens attained a length of about 4 cm, and developed plurilocular sporangia (Fig. 7A). They agree ~vit11 Cardinal's dercription of this species (Cardinal, 1964).

Fig. 5. A I'1z)~codr)~s r~ ibens . Different aspects of plants pickccl up from 20 nl depth west of Surtsey, August 24 1971; max. nat. size 8 cm. B. Ilelesseria sangz~inea. Young (right) and old (lcft) specimcns, the laLter one cowred,. partly by Membrarai$orn naenzbm- nacea; collectccl a1 20 m dcpth west of Surtscy, August 24 1971; max. nat. size 7 cm.

Giffordia ovata (Kjellm.) ICylin Typical specimens (Fig. 7B) bearing pluri-

locular sporangia grew up with the preceeding species in stock culture of Derbesia m.arina.

Chorda filzlm (L.) Stackh. This species which grew on stones amongst

Alnria escz~lenta at 10 m depth was found for the first time in 1977 off! the west coast. T h e plants were 60-70 cm long but sterile. This species has not previously been found growing in the West- man Islands.

Chorda tomentosa Lyngb. In 1977 several scattered individuals bearing

unilocular sporangia were found at 5 m depth on stones off the east coast. As the previously mentioned species this one has not been recorded in the Westman Islands before (Fig. 8B).

Ulothrix sz~bf laccida Wille This species was first found in 1971 on stones

at high tide level on the west coast growing amongst Ulothrix psel~doflacca and Urospora penicilliformis.

2. T h e vegelation

Fig. 6. Desmarestia acz~leatn. A fully grown plant from 20 n~ depth west of Surtsey, August 24 1071; nat. size 75 cm.

Derbesia marina (Lyngb.) Sol. In 1971 some specinlens were found growing

on calcareous Polychaeta tubes at 6-10 m depth off the west coast. Some of these plants bore lateral sporangia (Caram and Jbnsson, 1973).

Psez~dentoclonium submarinz~m Wille This species was found for the first time in

1971 g-rowing on solid rocks above high tide level on the east coast.

Other species mentioned in Table I have been reported on previously (J6nsson, 1970a, 1972).

a. Littoral zone. The substratum of the littoral zone is mainly of three types: huge blocks bordering the lava cliffs of the west, south and east coasts with gravel and sand in between, the boulder terrace occupying the southeast and northwest coasts and sand forming the northern spit (Fig. 1).

In 1971 and 1977 there had been minor changes in the littoral vegetation from that re- ported in previous years, i.e. there were still two algal belts, a green one, located at high tide level, and a brown belt below. Between 1971 and 1977 Alaria esce~lenta was found to have ex- tended its cover from the sublittoral zone into the brown belt of the tidal zone. The littoral vegetation appeared to be similar all along the rocky shore in both 1971 and 1977. No vegeta- tion was found on the northern spit and a very scanty one on the boulder terraces. A total of 16 species have been found growing on the shore, the most conspic~xous of' these at present being Enteromorpha prolifera. Other common species are Urospora penicilliformis, Ulothrix pseudo- flacca, Petalonia fascia (Fig. 9A), P. zosterifolia (Fig. 8A), Porphyra umbilicalis (Fig. 10A) and diatoms in mucilage threads. Scytosiphon lomen- tarius (Fig. 9B) is less common.

b. Sublittoral zone. The bottom from 0-30 m depth is of more or less uniform character around the island. It is mostly covered with big blocks of rock and boulders surrounded by gravel and sand. The rocky surfaces offer a suitable sub- strate for algal settle~nent. Around the northern spit the bottom is of sand and gravel with no visible vegetation.

In the sublittoral zone a total of 30 species were detected. Of these 19 were found in 197 1 and 27 in 1977. In 1977 11 species were found growing in all transects and the most commoir of these were Alaria esculenla (Fig. 1 I), Laminnria hyperborea (Fig. 12) and Desmaresl ia viridis (Fig. 13). These species were associated with several species of red algae, i.e. Phycodrys rtlbens (Fig. 5A), Delesseria sanguinea (Fig. 5B), Porphyra rniniata (Fig. 10B), Lomer~taria orcadensis (Fig. 14A), Polysipho~aia urceolata (Fig. 1413) and Anti thamnion floccosum.

In 1971 Desmarestia ligz~lata (Fig. 15) was a conspicuous element of the submarine flora all around the island. I11 1977, however, this species was found only off the south coast and represen- ted by a few small individuals. On the other hand,

Fig. 7. A. Gzffordza ?eczLtvata. A pait of a plant w1t11 pluriloc11lar spolangla; grew t ~ p In stock culture of algde collected at 10 m d c p t l ~ east of Surtsey, July 10 1977. I%. Gzffordia ovnla: part of a plant with plurilocula~ sporangia; grew up wit11 piereeding species.

Fig. 8. A. Pelrtlonia zosterifolia. Sterile specimens froin the littoral zone on the nortl~east coast of Surtscy, July 9 1977; max nat. size 10 cm. U. Chorda tomentosa. A fertile plant collected at 5 in cleptll northeast of Surtsey, July 9 1977; nat. length 32 cm.

Fig. 9. A. Petalonia fascia. A cluster of broad speci- mens collccted in the inter- tidal zone on the southeast coast of Surtsey, Augllst 27 1971; max. nat. sizc 4,s cm. B. Scylo.sipllon lot?le~zlnrius. A tuft of typical specimens from the intcrtidal zone on the cast coast of Surtsey, August 23 1971; max. nat. size G,7 cm.

Fig. 10. A. Porl~hyra to7ibilicalis. A fertilc plant from the intertidal zone on the east coast of Surtscy, August 23 1971; nat. size 4x7 cm. B. Porf~hyrcl tniiliata. Fertile plants from 5-10 111 depth so11tI1 of Surtscy, August 28 1971; max. nat. sizc 17,s cm.

Derbesiu marina and Lomentarin orcadensis had expancled since 1971. The former species was restricted to the west coast, but is now also gro~ving off the south coast. L . orcudensis was in 1971 only found on the south coast but in 1977 it occurred in all transects.

In the sublittoral zone the algae were randomly distributed on rock surfaces at a clepth range from 0 m to the lower limits of the vegetation at about 20 m depth, although fe~v individuals could be found clown to the depth of 30 m. This applies to both periocls of observa- tion. It was noted, that the Alaria esctclenta populations were moving tipwards, no1v occupy-

ing the lowest part of the tidal zone in several places. Luminaria hyperboreu, first detected on the island in 1967, was found to be most often grow- ing together with Desmareslia viridis. In 1971 the largest plants brought up from the bottorn had a stipe length of 8-10 cm and the blades were 25-30 cm long. Similarly, the largest plants collectecl in 1977 measured Ci3-64 cm in stipe length ancl 52-66 cm in blade length. They grew at 15 m depth and were 5-6 years old. Their stipes are frequently covereci xvith a luxurious growth of epiphytes. In addition to Hydrozoa and Bryozoa the following algal epiphytes were found on stipes and haptera ot Laminaria hyper-

Fig. 11. Alaria esczcle?ltn. Growth variations in plallts collcctccl

:kt 20 m tlcpth west of Silrtsey, August 24 1971; max. nat. size 62 cin.

Dorea: Polysiphonia z~rceolatu, Antitharnnion floccose~m, Callophyllis cristala (=Ee~thora cris- tutu), Lomentaria orcadensis, Giffordia sp. and Alaria escr~lenla. T h e blades are often covered ~ i t h large patches of Bryozoa.

An estimate of the algal biomass at Surtsey could not be made during our short survey. How- ever, samples taken with the underwater suction sampler within three quadrats at 10 m, 15 m and 20 m depth off the east coast revealed 7,9, 1,l and 0,2 kg/m" algal biomass, respectively.

There are actually two major seaweed beds in Surtsey waters, located off the east ancl the west coasts of the island. I n these ttvo localities the eroding action appears to be somewhat less than elsewhere along the coast (Norrman et al. 1974).

DISCUSSION All the new algal colonizers at Surtsey have

been found in similar habitats on the coasts of Iceland xvilh the exception of Gifforclia

Fig. 12. La~tzcnnria hyperbo~en . Well developed, typical speci- mclls from 10 m dcptll east of Surtsey, A I I ~ U S L 28 1'371; note epiphytes and epi7oa on stipcs ancl lamina; nat. s17c 85 cm.

reculvata ~ h i c l l TVaS llot previously known from Fig. 13. Desmarestia viriclis. A typical specimen fro111 12 111

Iceland. This species is regarded as very rare in depth south of Surtsey, August 28 1971; nat. size 25 cm.

4 1

Fig. 14. A. Lo?r~en tc l~ in orrclrle?rsis. A typical spccilnel~ from about 15 m depth southwest o f Surtsey. August 28 1971; nat. sizc 4 cm. B. Polysi$l~o?iicz r t~ceolatn. A spcci- men collected at 10 m depth south of Surtscy, Aug~~sl . 28 1'371; nat. sizc I) cm.

the North Atlantic (Cardinal, 1964). Of special 30 minutes for each dive. One must work quick- interest is the occurrence of Rhodophysema ele- ly and there is little time to explore vast areas gnns, found off the soutll coast o f Surtsey. This looliing for rare species. I n addition, dives are species is the first one o f the deep water crustose often extremely difficult and even dangerous. red algae found to colonize the island. Crustosc owing to surge and heavy sm~ell. corallinealgae were not found in spite of thorough Among the algal species colonizing Surtsey, search. The presence of Chorda filzcm ancl Chorda 23 were found in the littoral zone and 31 in the tomentosa at Surtsey is rather unexpected as these species have not been found growing ill the West- man Islands. T h e former is, however, a common driftweed on Surtsey and Heimaey. A similar r l r i -

~ ~ s u a l occurrence of Chorda lozmenlosa has been reported (as Halosiphon ton~enlosurn) from new lava flows in jail Mayen (Gulliksen 1974). Other species, such as Plocam,ium cartilaginez~m and Lomentar'ia clavellosa, are comnlon deep water red algae in the area and were already presumed as likely colonizers (J6nssoi1, 1967).

A total of 50 species of macroscopic algae have been identifiecl in the marine environment o f Surtsey since the beginning of the colonization 13 years ago. This represents about 42% of the total number of macroscopic algal species found to grow it1 the Westman Islands. I t appears that the marine algal colonization as a whole has been taking place by progressive immigration of species (Table I1 and Fig. 16). Ho~vever, year- to-year variations in species composition have been observecl during this period. This may be due to seasonal periodicity of short-lived algae and/or to the presence of opportunistic species. Also the possibility that individual species have been overlooked in the field should riot be rulecl

especially in the subtidal The length Fig. 15. Des,?,n~.estict ligz~lntn. A typical specilnell from 10 ~ l u

of time spent collecting underwater is olily 20- depth east of Sartsey, August 25 1'371; nac, size 70 cm.

42

TABLE 11 Marine algae and tlieir order o f arrival as recorded a t Surtsey 1!)(54-1977.

Species or groups

Diatoms . . . . . . . . . . Urospora i)enicilliforn~is . . . .

Ulolhrix flacca . . . . . . . .

Ulotlzrix psezidoflacca . . .

Enteroinorplzu flexuosa , . .

E~zterolnorpha ir~te.sti?zalis . .

I'ylaiella littoralis . . . . .

Eclocccrj~tis confclvoidc.~ . . .

Scytosipho7z l o t t ~ e ~ ~ l a r i ~ t s . .

. . . . . . Petnlolzia fasc:ci . . . Petnlo~zia zosterilolia

Alaria escz~lenla . . . . .

Por$hyra zcn~bilicc11i.s . . . . . .

. . . . . . Corlioluin g r e g a r i ~ i ~ ~ l Eizteronzorpha linza . . . .

. . . . Enteron~orplza coltlfireascl Acrosipltoi~ia crrcta (= A. spinesce~ Giffortlia I~ii~cltsiae . . . . . .

Des~~zarestia f~iridis . . . . .

Ulotllrix consociala . . . . .

Urosl)orcl zuorr~~skioldii . . .

E~zlero~t lor l~ha firolifera . . . .

Monostro~na grevillei . . . .

La~ni~rar ia Izyperborea . . . .

Des~t~are.stia ligzilala . . . . . .

Des?t~nre.slin acz~lec~la . . . . .

Porflhym pzcrp~irea . . .

. . . . . Porpl~yra nziizialri Lon~entaria orcurlensis . . . .

. . . Anl i than~nion floccoszert~ Phycotirys rzcbeizs . . . . .

Polysifihonia tirceolata . . . .

,Giffordia ~ ~ ( I I Z L L ~ O S ~ . . . . . .

Blue-Green Algae . . . . . .

U ~ I J ~ lactzcca . . . . . . . .

Lamil~nria cligilata . . . . . .

Eutlzora cristata . . . . . . . .

Derbesia ~nar ina . . . . . . . .

Pseuclentoclonizirn su b l / J a r i n ~ m Ulotlrrix s~cbflaccitla . . . . . .

,Gifforclia secunda . . . . . .

Ralfsia sp. . . . . . . . . . .

Rhoclochorton f i~~rpzcreuin . . Delesseria sangzcinea . . . . . .

Ectocarpus siliczclosus . . . .

Giffordia ovata . . . . . . . .

-Giffordia recurvata . . . . . .

. . . . . . . Chorda filu?n Chorda toineiztosa . . , . .

Plocamizcitz cartilaginezinz . .

Rkoclophysema elegans . . . .

Lome~ztaria clauellosa . . . .

Antithrc~nizion plz~iiaz~la v . borcale Conchocelis rosea . . . . . .

.sublittoral zone. Of these, 4 species have settled observation has been made for intertidal pioneer in both zones. A striking fact is that the populations of algae on lava flows in the Hawaii- colonization in the littoral zone has not progres- an Islands (Doty, 1967). This situation may be as- .sed markedly since the occupation by ,some cribed to the harsh environmental conditions it1

pioneer species as early as 1966 (Fig. 16). Asimilar the intertidal zone. The most important limiting

specles number t A ~n te r t rda l + subt idal

0 i n te r t ida l

subt idal

A

Fig. 16. 'The ilulllber of spc~ies of marine algae (diatoms not included) rccorded froin Snrtscy since the beginning of the scttle- mcnt; note the statiorlaiy situation in tlxc intertidal zoilc contlasting will1 a progressive colo~lizatio~~ in the subtiddl zo~lc.

factors are presumably the scouring action by sand and pumice, in addition to the mobility of the substrate due to wave abrasion along the lava clifl-'s and movement of abraded material. I t may therefore be expected that the pioneer stage in the littoral zone of Surtsey will last until the stability of the substrate has been reached. As a contrast to this situation the algal colonization of the sublittoral zo11e has beer1 progressing faster although starting later (Fig. 16). T h e dif- ference may be attributed to a more stable en- vironment.

As stated above, oilly a few subtidal species are actually of ecological importance. These are Alaria esculenta, Laminaria hyperborea and Desmarestia airidis, which were first recorded in 1966, 1967 and 1968, respectively. I t is to be noted that the colonization by these species at Surtsey has not proceeded by sera1 stages of succession similar to those described for artificially or ac- cidentally denuded plots in old floral areas (den Hartog, 1959, Norton and Burrows 1967). Probably, no competitive relations of species will set in as long as there are sufficient vacant places for the new colonizers and their descendants. This problem must be solved on a quantitative basis.

ACKNOWLEDGEA4ENTS Thanks are due to Dr. Bernadette Caram who

identified the brown algae during the 1971 field trip to Surtsey and to Erlillgur Haultsson who participated in the diving work. Our thanks go

also to Erlingur Hauksson, JGhannes Uriem, J6n ~ la f sson , KonrAd Th6risson, 0 l i R. Snmarlida- son and Sigurdur V. Hallsson for their assistal~ce during dives in 1977.

T h e field work was partly sponsored by the Icelandic Science Fund. and by the Surts- ey Research Society. R / V Arni Fridrilzsson was provided by the Marine Research Iilstitute, Reykjavik, during the 1977 field work.

ADDENDUM Since the preparation of this paper the marine

benthic diatoms collected in Surtsey during the survey in 1977 have been worked u p by Marie- France Simon, Laboratoire cle Biologie V6gktale Marine, Paris University. T h e species identified are given in the follo~ving list. Many of these have been previously reported from Iceland (E. Bstrup: Marine Diatoms from the coast of Ice- land, Bot. Icel., 2: 347-398, 1918). New records are printed in italics.

Amphipleura rutilans (Trentepohl) Cleve; lit- toral W.

Amphora lurgida Greg.; littoral E. Biddulphia obtusa (I<iitzing) Ralfs; littoral W. Grammatophora marina (Lyngbye) Kiitzing: sub-

littoral W. Grammatophora serpentina (Ralfs) Ehrenberg v.

pusilla (Greville) Peragallo; sublittoral W. Isthmia enewis Ehrenberg; sublittoral E. Licmophora abbreviata Agardh; littoral E.

Licmophora toral W .

Licmophora Licmophora

c o m m u n i s (Heiberg) Grunow; lit-

hyulina ICutzing; littoral W . jurgensii Agardh (11,. oedipus

(Kutz.) Grunow); littoral W. N a v i c z ~ l a gracilis Ehrenherg; littoral E. iSavicula grevillei (Agardh) Cleve; sublittoral W. N a v i c z ~ l a lanceolata (Agardh) Kiitzing; littoral E. Navicula lanceolata v.phyllepta (ICiitzing) Cleve;

littoral E. Navic~xla ralnosissima (Agarclh) Cleve; littoral

and sublittoral E and W. N a u i c l ~ l u Lenuis (Agardh) A. Cleve; littoral E. Niizschia migrans Cleve; littoral W . Rhabdonema adriaticum ICiitzing; littoral and

sublittoral W. Synedra investiens W. Smith; littoral E and W. Synedra pulchella (Ralfs.) ICiitzing; littoral W

and E.

References: Car;t~n, B. ;ind S. J6nsson, 1972. Nouvel invcntaire clcs algues

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J611ssori, S., 1967. I~urtl ier sc t t le~ne~l l of marine belltl~ic algac on the rocky shore of Srtrtscy. S~urtscy Res. Progr. Report, 3: 46-56.

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