PRELIMINARY STUDY OF THE INTERTIDAL COMMUNITIES OF MAXWELL BAY, KING GEORGE ISLAND, SOUTH SHETLANDS ARCHIPELAGO, ANTARCTICA Ahmed Aghmich, Lluis Toll, Sergi Taboada and Manuel Ballesteros 1 Departament de Biologia Animal, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal, 643, 08028 Barcelona, Spain. 1 corresponding author: mballesteros@ub.edu INTRODUCTION The study of the marine organisms inhabiting the Southern Ocean have attracted scientists since the first expeditions had access to the white continent or to nearby islands. Some general studies and overviews of the Southern Ocean benthic biodiversity within the last two decades have shown that the marine invertebrate fauna is rich and diverse (Arntz, W.E., Gutt et al, 1997). In certain areas of the Antarctic coastline, mainly the ones located in the vicinities of scientific bases, the numerous biodiversity or ecological studies undertaken have allowed a good understanding of the marine communities, their composition and distribution. This is the case of King George Island, at the South Shetland Archipelago (Arnaud et al, 1986) and Adelaide Island (Barnes & Brockington, 2003). The studies of the intertidal Antarctic and sub-Antarctic are comparatively scarce than those from the sublittoral and the deep sea. However, within the last years some studies have been conducted to explore the biodiversity, distribution and abundance of intertidal organisms (Waller, 2008). In our study, qualitative and quantitative samples were taken during the Spanish BENTART 2006 Antarctic expedition with the aim to know the composition and abundance of the invertebrate fauna that lives in the intertidal rocky platform of Fildes Bay (= Maxwell Bay), King George Island, South Shetland Archipelago. This platform is dominated in its middle and lower area by the brown algae Adenocystis utricularis that can cover up to 100% of the rocky surface; in the lowest area of the platform are numerous rocky tide pools where the rhodophyceae Iridaea cordata is the dominant algae. RESULTS Quantitative samples of 20 x 20 cm yielded a total of 9950 individuals of 38 species or higher taxa belonging to the taxonomic groups of Mollusca, Polychaeta and Crustacea (Table I). The relationship between species, their distribution in the different samples and their abundance is reflected in Table II. In these quantitative samples we also identified fragments of 3 Bryozoa species (Inversiula nutrix, Antarctothoa bouganvillei , Eschenoides tridens), which are not quantified in the tables because it is not possible to determine whether they belong to one or more colonies. METHODOLOGY Sampling took place in January 2006 on the intertidal platform in the north of Fildes Bay (62°12'4"S 58°57'45"W), to about 500m away from the Bellingshausen Russian base, where tidal sea floor reveals an important area of bedrock, almost flat with tide pools. Tidal height was 0.13 meters at the time of sampling. DISCUSSION The intertidal environment of Antarctica is perhaps the marine environment subjected to the most extreme environmental conditions in the world (drying, very low temperatures, ice cover in winter, freshwater flow in summer, UV irradiation). For this reason,intertidal communities have been considered to be poor in terms of biodiversity. However, studies over the last decade are showing a very different reality (Kim, 2001). Our surveys made in the intertidal platform of Fildes Bay have shown an extraordinary abundance of small invertebrates associated with algal thalli on the platform, the phaeophyceae Adenocystis utricularis and the rhodophyceae Iridaea cordata, with values reaching up to nearly 100.000 individuals per square meter. These data are consistent with those obtained by Bick et al. (2013) at soft substrate samples in the same area. The most abundant species in quantitative samples was Eatoniella kerguelenensis regularis (6763 individuals), a small herbivorous gastropod that find food and shelter mainly among Adenocystis fronds. The bivalve Kidderia subquadrata has homocromy with the algal fronds of Iridaea cordata and has proved to be very abundant on this alga (528 individuals in sample 4), although has also appeared in Adenocystis samples (211, 1046 and 175 in the samples 1, 2 and 3). The significant difference (p-value: 0.0274) of the Shannon entropy between the two communities can be explained by the fact that Iridaea community was in a tidal pool where environmental conditions may be more stable. Instead, the three samples of A. utricularis were completely uncovered by the water. Although these differences appear significant, this study is preliminar and further sampling would required to obtain ecologically significant results. The Shannon entropy data obtained in our work are significantly lower (2,61 to 3,06) than those obtained by Bick & Arlt (2013) mainly due to the extraordinary abundance of 3 species of mollusks (Kidderia subquadrata, Laevilitorina caliginosa, Eatoniella kerguelenensis regularis) and a crustacean (Cheirimedon femoratus), which is also reflected in the lower values of Pielou evenness. These authors cited in their work the presence of 18 species of invertebrates in the intertidal phytal and hard substrate qualitative study. Our work increases significantly the biodiversity Knowledge of invertebrates that live in the intertidal rocky platform of Fildes Bay, with 51 species. Fig.2 1 Intertidal platform of Maxwell Bay at samplig moment. 2 Sampling area in Adenocystis utricularis community. 3 Community of Iridaea cordata. Three quantitative samples (S1, S2, S3) of 20 x 20 cm were taken from a community of the phaeophycean algae Adenocystis utricularis and one additional sample (S4) of 20 x 20 cm was taken from the tide pool community dominated by the gigartinacean rhodophyceae Iridaea cordata. In addition, qualitative samples of invertebrates that live under the boulders were taken. In situ photographs were taken from the sampling area and also from the main invertebrates, both in the field and in the laboratory. Samples were filtered through a 200 μm sieve and fixed in 70% alcohol at the Profesor Julio Escudero Chilean Antarctic Base. Invertebrates from the samples were separated, quantified and identified in the Department of Animal Biology, University of Barcelona. For quantitative samples we analyzed the abundance of the different species using the Shannon-Wiener diversity index. Fig.1 Fildes Peninsula in King George Island showing the sampling site in Maxwell Bay. Table I Invertebrates groups’s abundance, Shannon- Wiener diversity H’ and Pielou evenness J of all the samples (S1, S2, S3 and S4). Table II Species abundance and distribution in the quantitative (Qt) and qualitative (Ql) samples. N total of individuals in samples (S1,S2,S3 and S4). Ov Ovigera capsules. References -Arnaud, P.M., Jazdzewski, K., Presler, P. & Sicinski, J. 1986. Preliminary survey of benthic invertebrates collected by Polish Antarctic Expeditions in Admiralty Bay (King George Island, South Shetland Islands, Antarctica). Pol. Polar Res., 7, 7-24. -Arntz, W.E., Gutt, J., Klages, M., 1997. Antarctic marine biodiversity: an overview. In:Battaglia, B., Valencia, J., Walton, D.W.H. (Eds.), Antarctic communities: species,structure and survival. Cambridge University Press, Cambridge, pp. 3–14. -Barnes, D.K.A. & Brockington, S. 2003. Zoobenthic biodiversity, biomass and abundance at Adelaide Island, Antarctica. Marine Ecology Progress Series, 249:145-155. -Bick, A. & Arlt, G. 2013. Description of intertidal macro- and meiobenthic assemblages in Maxwell Bay, King George Island, South Shetland Islands, Southern Ocean. Polar Biol., 36:673-689 -Kim, D. 2001. Seasonality of marine algae and grazers of an Antarctic rocky intertidal, with emphasis on the role of the limpet Nacella concinna Strebel (Gastropoda: Patellidae). Ber. Polarforsch. Meeresforsch. 397, 136 pags. -Waller, C. L. 2008. Variability in intertidal communities along a latitudinal gradient in the Southern Ocean. Polar Biology, 31:809-816. Eatoniella kerguelenensis regularis Kidderia subquadrata Cheirimedon femoratus Eusyllinae sp2 Nacella polaris Antarctonemertes riesgoae Inversiula nutrix Parborlasia corrugatus Obrimoposthia wandeli Antarctonemertes valida ovigera capsules Harpagifer antarcticus Laevilitorina caliginosa Granaster nutrix Adelasterias papillosa From the qualitative sampling we identified 18 species, 10 of which did not appear in the quantitavive samples. Two of these species are echinoderms from the family Asteriidae, Granaster nutrix and Adelasterias papillosa, frequent below the stones of the shore. Also on the underside of stones we found an abundance of small size fauna such as the plathyelmintha tricladida Obrimoposthia wandeli, the nemerteans (Parborlasia corrugatus, Antarctonemertes valida and A. riesgoae), encrusting bryozoans (Inversiula nutrix), mollusks (Kidderia subquadrata, Laevilitorina caliginosa), lots of tiny calcareous tubes of Spirorbinae polychaeta and the fish Harpagifer antarcticus. Numerous individuals of the patellogastropodan Nacella polaris appeared in the middle tidal area, which tend to congregate at the edges of the large tide pools or inside small buckets that remain above the rocks. Mollusks were most abundant group in all quantitative samples with 9522 individuals, being the gastropoda Eatoniellidae (6817 individuals) and Littorinidae (576) and the bivalvia Cyamiidae (1960 individuals) the most abundant families. Crustacea and Polychaeta were represented by 295 and 133 individuals, respectively. Among Polychaeta, the families Syllidae (44 individuals), Terebellidae (37 individuals) and Phyllodocidae (24 individuals) were the most abundant while the family Lysianassidae (order Amphipoda) was for Crustacea. Polychaeta was the taxonomic group with a higher specific diversity with 21 species, particularly families Syllidae (5 species) and Phyllodocidae (3 species), followed by Mollusca (11 species) represented by gastropods (8 species) and bivalves (3 species). The group of Crustacea was represented by 7 species (Amphipoda 6 species). Using the specific and abundance data obtained in the sampling area, and computing the quadratic entropy of Shannon, we obtained intervals of biodiversities with 95% confidence. The results obtained are shown in Table I. Shannon-Wiener biodiversity of Iridaea cordata community is higher (1,577) than in community of Adenocystis utricularis (values from 0,803 to 1,004). The low Pielou´ s values show clearly that there is a big difference between the species´ abundance. Laevilacunaria antarctica Bovallia gigantea ABUNDANCE S1 S2 S3 S4 ind x 0,04m 2 ind x m 2 ind x 0,04m 2 ind x m 2 ind x 0,04m 2 ind x m 2 ind x 0,04m 2 ind x m 2 MOLLUSCA 3093 77325 3801 95025 1558 38950 1070 26750 CRUSTACEA 185 4625 49 1225 45 1125 16 400 POLYCHAETA 8 200 42 1050 16 400 67 1675 TOTAL 3286 82150 3892 97300 1619 40475 1153 28825 H' diversity 0,803 ± 0,030 0,891 ± 0.027 1,004 ± 0,055 1,577 ± 0,069 J evenness 0,313 0,314 0,362 0,455 Taxon Qt Ql S1 S2 S3 S4 N PLATYHELMINTHES Obrimoposthia wandeli (Hallez,1906) xxx Tricladida sp x NEMERTEA Antarctonemertes valida (Bürger, 1893) xx Ov A. riesgoae Taboada, Junoy x Andrade, Giribet, Cristobo & Avila, 2013 Parborlasia corrugatus (McIntosh, 1876) x POLYCHAETA Phyllodocidae sp 2 10 12 Eteone sculpta Ehlers,1897 1 1 Austrophyllum cf.charcoti (Gravier, 1911) 2 9 11 Dorvilleidae sp 1 1 Leitoscoloplos kerguelensis 2 2 (McIntosh, 1885) sensu Ramos 1976 Nereidae sp 1 1 2 Sphaerodoridae sp 1 1 Chaetozone sp 4 4 Cirratulidae sp 1 2 1 4 Polycirrus sp1 1 8 9 Polycirrus sp2 1 1 Terebellidae sp 19 2 6 27 Sabellidae sp 1 1 Micronephthys sp 1 1 2 Capitellidae sp 6 5 11 Eusyllinae sp1 1 1 2 4 Eusyllinae sp2 1 3 4 Eusyllinae sp3 2 10 8 8 28 Exogone sp1 7 7 Exogone sp2 1 1 Spirorbinae sp indet. xxx MOLLUSCA BIVALVIA Kidderia subquadrata (Pelseneer, 1903) 211 1046 175 528 1960 20 Mysella charcoti Lamy, 1906 1 11 12 Lissarca miliaris (Philippi, 1845) 18 18 36 MOLLUSCA GASTROPODA Nacella polaris (Hombron & Jaquinot, 1841) 1 6 7 xxx Eatoniella kerguelenensis regularis 2545 2614 1214 390 6763 (E.A.Smith, 1915) Eatoniella caliginosa (E.A.Smith, 1875) 8 46 54 Laevilitorina caliginosa Gould, 1849 329 104 39 472 xxx Laevilitorina umbilicata 3 16 32 62 113 Pfeffer in Martens & Pfeffer, 1886 Laevilacunaria antarctica (Martens, 1885) 5 20 70 5 100 1 Pellilitorina pellita (Martens, 1885) 4 4 Trochidae indet.juv 1 1 MOLLUSCA POLYPLACOPHORA Polyplacophora sp x CRUSTACEA Epimeria monodon Stephensen, 1947 1 1 Cheirimedon femoratus (Pfeffer, 1888) 184 48 45 2 279 71 Bovallia gigantea Pfeffer, 1888 1 1 38 Eurymera monticulosa Pfeffer, 1888 7 7 15 Gondogeneia antarctica (Chevreux, 1906) 1 3 4 Gammaridea sp 1 1 Isopoda indet. 2 2 BRYOZOA Inversiula nutrix Jullien, 1888 x x xxx Antarctothoa bougainvillei (d'Orbigny, 1842) x x Escharoides tridens (Calvet, 1909) x ECHINODERMATA Granaster nutrix (Studer, 1885) 4 Adelasterias papillosa (Koeler, 1906) 5 PISCES Harpagifer antarcticus Nybelin, 1947 2