Krzysztof Jażdżewski, Jacek Siciński, Piotr Presler Laboratory of Polar Biology University of Łódź, Poland

XX Polar Symposium Lublin, 1993

REMARKS ON THE BOTTOM FAUNA OF ADMIRALTY BAY, SOUTH SHETLANDS, ANTARCTICA*

The foundation of Polish Antarctic Station „Henryk Arctowski" in 1977 allowed to conduct year round intensive studies on zoobenthos of Admiralty Bay using a variety of sampling techniques like dredging, bottom-grab sampling, baited traps and SCUBA diving collectioning and observations. Early prelimina-ry notes (Jażdżewski 1981, 1983, Lipiński and Woyciechowski 1982, Urbanek and Zieliński 1982) were soon widened into more synthetic papers (e. g. Arnaud et al. 1986, Jażdżewski et al. 1986, Presler 1986, Siciński 1986, Jażdżewski et al. 1991 a, b). Participation in 3 winterings and 4 summer-season expeditions to the „Arctowski" Station allowed the members of the Laboratory of Polar Biology, University of Łódź to collect over 1000 qualitative and quantitative samples of the bottom fauna. Only a part of this huge material is sorted and determined. Hitherto obtained results, published in the above listed papers, are here briefly summarized and new data are added.

The early list of over 200 benthic invertebrate taxa of Admiralty Bay (Arnaud et al. 1986) is now nearly doubled. Only three more thoroughly studied groups — Polychaeta, Amphipoda and Ophiuroidea — embrace now about 250 taxa (Siciński 1986, Jażdżewski et al. 1991 a, b, Presler 1992, Siciński and Janowska, in press).

Qualitative studies carried out in three transects using a Van Veen grab at depths from 15 to 250 m in the season 1979/80 have given following results (Jażdżewski et al. 1986). Considerable abundancies of bottom fauna as well as biomass values were found. Maximal abundance observed was over 36000 ind -m - 2 with an average of ca 6500 ind • пГ2, maximal biomass was over 2400 g-m~2, while the average surpassed 700 g-m"2. At the depth of 15 m bivalve molluscs clearly dominated constituting over 85% of all animals and nearly 58% of the total weight. At the depth of 30 m Bivalvia were still dominant in numbers but yielded to other groups in terms of biomass. In stations situated at 80, 150 and 250 m Polychaeta were dominant group in terms of abundance but in terms of biomass Ascidiacea, Echinoidea and Ophiuroidea were the leading animal

* More detailed presentation of these problems is published elsewhere (Jażdżewski К., Siciński J., 1993. Zoobenthos, 12.1. General remarks. In: Admiralty Bay, Antarctica. Ed. S. Rakusa--Suszczewski, Warszawa, 300 pp).

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groups. Amphipoda contributed siginificantly to the bottom fauna abundance at all depths but they were less important in terms of biomass. The biomass of Ascidiacea alone at the depth of 80 m surpassed 2000 g • nr2 ; that of Bryozoa at the depths of 30, 80 and 150 m was considerable.

Next quantitative studies of the Admiralty Bay bottom were undertaken during austral summer 1987/88. Using a SCUBA diving technique we have operated at the Shag Point near the „Arctowski" Station more or less in the same transect as transect I of the former studies. A Tvarminne-type bottom sampler was used (Kangas 1972) at depths from 4 to 30 m. The results are also published recently (Jażdżewski et al. 1991b). These observations in summary were as follows. Leading animal groups were Polychaeta, Bivalvia and Amphipoda. Total animal abundancies varied between 2000 and 25000 ind • m~2 being therefore quite comparable to the results of Wagele and Brito (1990) who have studied macrozoobenthos near the Brazilian „Ferraz" Station in Martel Inlet of Admiralty Bay. Very similar was also a distinct dominance of bivalves, mostly of Mysella charcoti, at the depth of 6.5 m as well as a high share of serolids (probably also Serolis polita) at the depths of 4 and 6.5 m. A remarkable difference observed was a very high share of Amphipoda in nearly all sampled stations at Shag Point. This group dominated in terms of abundance at depths from 10 to 25 m constituting over 60% of all collected animals. In therms of biomass these crustaceans, because of their generally small individual size, were less significant components of zoobenthos, yielding to other groups (Echinoidea, Polychaeta, Serolidae, Bryozoa) at particular depths.

This difference can be due to the fact that the sampling transect of Polish scientists was situated in a non-sheltered region of the Admiralty Bay and, in comparison with Martel Inlet, less influenced by the sedimentation of suspended matter coming with an inflow of melting glaciers water (Pęcherzewski 1980, Lipski 1987). Moreover, in our samples, in principle taken in the soft bottom, a significant role as an element of bottom substrates, was played by broken, fresh or decaying fragments of algae. This detritus created a habitat suitable for species typically connected with neighbouring phytal zone (Zieliński 1990, Jażdżewski et al. 1991b).

The above results of the detailed quantitative studies can be supplemented by some not yet published data. During the wintering of IXth Polish Antarctic Expedition (1984/86) the second author has collected some 20 additional Van Veen grab samples outside the transects treated in the paper by Jażdżewski et al. (1986). Joint elaboration of our all quantitative Van Veen samples is presented in Tab. 1 and in Fig. 1. An attempt was made to evaluate roughly the biomass of Admiralty Bay, calculating it for the bottom surface between particular 50 m isobaths.

Some general idea on the biomass of bottom invertebrates of Admiralty Bay can be drawn from the overall mean calculated for some 70 Van Veen grab

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samples (sampling surface 0.09 m2) taken from nearly whole depth range (4-500 m). This mean amounts to abt. 700 g -m~2 and its 95% confidence limits are 500 and 900 g пГ2. For particular depth ranges means are different and the distribution of these values shows a definite tendency. Rather low biomass of shallow sublittoral (200-400 g • mf2) increases to the maximal mean of 1400 g • m~2

in the depth range of 100-200 m and then diminishes to about 300 g • m"2 in the range 300-500 m.

Good presentation of the biomass richness of zoobenthos of Admiralty Bay, that is, due to the abundant occurrence of large ophiuroids and ascidians, are the photographs of the bottom of the Bay at the depths of 90 and 300 m made by the remote operating camera.

A distinct feature of the Admiralty Bay zoobenthos is its patchy distribution. In some depth zones the differences between the extreme values of the biomass obtained from particular sampling units (grabs) were of two orders of magnitude. Even in rather closely situated areas the bottom fauna biomass varied between some scores of grams and some kilograms per squ. m. In some places where Ascidiacea were very abundant maximal values obtained ranged up to 7 kg of wet weight per squ. m. Confidence limits (95%) were the widest for the depth range 100-200 m. At these depths the patchiness as well as mean values of biomass of zoobenthos were the highest.

One can observe some tendencies in the distribution of particular animal groups. Biomass of ubiquitous Polychaeta that are abundant all over the Bay, is clearly the lowest in the shallowest sublittoral to the depth of 30 m. Rich assemblages of Ascidiacea occur at depths from 30 to 300 m, whereas above the depth of 30 m and in deep water (300-500 m) they occur sporadically and their share in benthos biomass is negligible. Similar tendency was also observed for Bryozoa. Brittle stars (Ophiuroidea) are abundant at depth ranging from 30-40 m to abt. 400 m.

In general one can observe that the isobath of some 30 m is a rather important zoocenological boundary in the central part of Admiralty Bay. From that very depth a mass occurrence of Bryozoa and Ascidiacea begins. Of course these animals usually attached to the drop-stones have especially patchy distribution but in the coarse scale these groups decide on the total zoobenthos biomass. Below some 300 m both Bryozoa and Ascidiacea, as well as Ophiuroidea become much less numerous, zoobenthos patchiness decreases and mean benthos biomass diminishes.

The composition of bottom fauna of Admiralty Bay, being still not sufficiently studied, can be, however, a good exemplification of hitherto formulated generalizations concerning the Antarctic sublittoral. The qualitative and quantitative richness of Antarctic zoobenthos so often recorded and discussed (for review see Arnaud 1974, Jażdżewski 1983, White 1984, Picken 1985, Jażdżewski et al. 1986, Gallardo 1987, Muhlenhardt-siegel 1988, Gerdes

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et al. 1992) can be clearly observed in Admiralty Bay. At the same time diversified biota of this rather large and deep basin, different hydrological conditions in its particular parts (viz. Pęcherzewski 1980, Pruszak 1980, Samp 1980, Szafrański and Lipski 1982, Lipski 1987) and especially sedimentation type and the quality of bottom sediments cause that the zoobenthos is also diversified in terms of species richness, abundance of populations as well as biomass of assemblages.

In general one can find clear and near similarities of Admiralty Bay zoobenthos communities to those observed at South Orkney Islands (Everson and White 1969, Hardy 1972, White and Robins 1972 and Picken 1985) as well as those recorded by Rauschert (1991) for Maxwell Bay. Zoobenthos of sheltered embayments of Admiralty Bay resembles that of also sheletered areas of Arthur Harbour (Anvers Island, Palmer Archipelago) and of Chile Bay (Greenwich Island, South Shetlands) — as found by Lowry (1975) and Richardson and Hedgpeth (1977) as well as by Gallardo and Castillo (1969) and Gallardo et al. (1977), respectively.

The list of dominant macrozoobenthos species presented by Zam orano (1983) for South Bay (Doumer I., Palmer Archipelago) very closely resembling the faunistic results obtained for similar habitats of King George Island by Wagele and Brito (1990), Rauschert (1991) and the present authors as well as all above mentioned similarities of Admiralty Bay and Signy Island benthos clearly support the inclusion of South Orkneys, South Shetlands and Palmer Ar-chipelago into the same biogeographical Scotia subregion (Hedgpeth 1969).

All above cited papers revealed that the typical West-Antarctic sublittoral bottom fauna is highly diverse; its composition and abundance depends primarily on the quality of sediments. This bottom fauna is extremely rich in species and individuals and this abundance and biomass surpasses those observed in other oceanic regions.

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Everson I. & M. G. White, 1969: Antarctic marine biological research methods involving diving. Rep. Underwat. Ass., 4: 91-95.

Gallardo V. A., 1987: The sublittoral macrofaunal benthos of Antarctic shelf. Env. Intern., 13: 71-81.

Gallardo V. A. & J. G. Castillo, 1969: Quantitative benthic survey of the infauna of Chile Bay (Greenwich Island, South Shetlands). Gayana, 16: 1-18.

Gallardo V. A., J. G. Castillo, M. A. Retamal, A. Yanez, H. Moyano & J. G. Hermosilla, 1977: Quantitative studies on the soft-bottom macrobenthic animal communities of shallow Antarctic

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bays. In: Adaptations Within Antarctic Ecosystems, ed. G. A. Llano, Proc. 3-rd. SCAR Symp. Antarct. Biol., Smith. Inst. Wash.; 361-367.

Gerdes D., M. Klages, W. E. Arntz, R. L. Hermann, J. Galeron & S. Hain, 1992: Quantitative investigations on macrobenthos communities of the southeastern Weddell Sea shelf based on multibox corer samples. Polar Biol., 12: 291-301.

Hardy О., 1972: Biomass estimates for some shallow-water infaunal communities at Signy Island, South Orkney Islands. Br. Antarct. Sur. Bull., 31: 93-106.

Hedgepth J. W., 1969: Introduction to Antarctic Zoogeography. In: Antarctic Map Folio Series, Distribution of Selected Groups of Marine Invertebrates in Waters South of 35°S Latitude, eds. V. C. Bushnell & J. W. Hedgpeth, Amer. Geogr. Soc., New York; 1-9.

Jażdżewski К., 1981: Amphipod crustaceans in the diet ofpygoscelid penguins of the King George Island, South Shetland Islands, Antarctica. Pol. Polar Res., 2: 133-144.

Jażdżewski К., 1983: Fauna denna Antarktyki i udział Polaków w jej poznawaniu. Kosmos, 32: 231-250.

Jażdżewski К., C. De Broyer, W. Teodorczyk & A. Konopacka, 1991a (1992): Survey and distributional patterns of the amphipod fauna of Admiralty Bay, King George Island, South Shetland Islands. Pol. Polar Res., 12: 461-472.

Jażdżewski К., W. Jurasz, W. Kittel, E. Presler, P. Presler & J. Siciński, 1986: Abundance of Biomass Estimates of the Benthic Fauna in Admiralty Bay, King George Island, South Shetland Islands. Polar Biol., 6: 5-16.

Jażdżewski К., W. Teodorczyk, J. Siciński & В. Kontek, 1991b: Amphipod crustaceans as an important component of zoobenthos of the shallow Antarctic sublittoral. Hydrobiologia, 223: 105-117.

Kangas P., 1972: Quantitative sampling equipment for the littoral benthos. II. IBP, Norden, 10: 9-16.

Lipiński M. & M. Woyciechowski, 1981: Cephalopods in the food of Weddell seals from the Admiralty Bay (King George Island, South Shetland Islands). Pol. Polar Res., 2: 163-167.

Lipski M., 1987: Variations of physical conditions, nutrients and chlorophyll a contents in Admiralty Bay (King George Island, South Shetland Islands, 1979). Pol. Polar Res., 8: 307-332.

Lowry J. K., 1975: Soft bottom macrobenthic community of Arthur Harbor, Antarctica. Antarctic Res. Ser., 23: 1-19.

Miihlenhardt-Siegel U., 1988: Some Results on Quantitative Investigations of Macrozoobenthos in the Scotia Arc (Antarctica). Polar Biol., 8: 241-248.

Pęcherzewski К., 1980: Distribution and quantity of suspended matter in Admiralty Bay (King George Island, South Shetland Islands). Pol. Polar Res., 1: 75-82.

Picken G. В., 1985: Marine Habitats-Benthos. In: Key Environments: Antarctica, eds. W. N. Bonner & D. W. H. Walton, Pergamon Press; 154-172.

Presler P., 1986: Necrophagous invertebrates of the Admiralty Bay of King George Island (South Shetland Islands, Antarctica). Pol. Polar Res., 7: 25-61.

Presler P., 1992: 12. Zoobentos, 2. Ophiuridae. In: Zatoka Admiralicji. Antarktyka, ed. S. Rakusa-Suszczewski, Ofic. Wyd. Inst. Ekol. PAN, Dziekanów Leśny; 141-145.

Pruszak Z., 1980: Currents circulation in the waters of Admiralty Bay (region of „Arctowski" Station on King George Island). Pol. Polar Res., 1: 55-74.

Rauschert M., 1991: Ergenisse der faunistischen Arbeiten im Benthal von King George Island (Sudshetlandinseln, Antarktis). Ber. Polarforsch., 76: 1-76.

Richardson M. D. & J. W. Hedgpeth, 1977: Antarctic Soft Bottom Macrobenthic Community Adaptations to a Cold, Stable, Highly Productive, Glacially Affected Environment. In: Adaptations Within Antarctic Ecosystems, ed. G. A. Llano, Proc. 3-rd SCAR Symp. Antarct. Biol., Smith. Inst. Wash.; 181-196.

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Samp R., 1980: Selected environmental factors in the waters of Admiralty Bay (King George Island, South Shetland Islands), December 1978-February 1979. Pol. Polar Res., 1: 53-66.

Siciński J., 1986: Benthic assemblages of Polychaeta in chosen regions of the Admiralty Bay (King George Island, South Shetland Islands). Pol. Polar Res., 7: 63-78.

Siciński J. &E. Janowska, in press. Polychaetes of the shallow sublittoral of Admiralty Bay (King George Island, Antarctica) with some general remarks on the polychaete assemblages of the Antarctic sublittoral. Antarctic Science.

Szafrański Z. <6 M. Lipski, 1982: Characteristics of water temperature and salinity of Admiralty Bay (King George Island, South Shetland Islands, Antarctic) during the austral summer 1978/79. Pol. Polar Res., 3: 7-24.

Urbanek A. & K. Zieliński, 1982: Preliminary report on Cephalodiscus (Pterobranchia) from Admiralty Bay, King George Island, South Shetland Islands (West Antarctica). Bull. Acad. Pol. Sci., 29: 257-262.

Wagele J. W. & T. A. S. Brilo, 1990: Die sublitorale Fauna der maritimen Antarktis. Erste Unterwasserbeobachtungen in der Admiralitatsbucht. Natur und Museum, 120: 269-282.

White M. G., 1984: Marine benthos. In: Antarctic ecology, 2. ed. R. Laws, Academic Press, London, 421-461.

White M. G. & M. W. Robins, 1972: Biomass estimates from Borge Bay, Signy Island, South Orkney Islands. Br. Antarct. Surv. Bull., 31: 45-50.

Zamorano J. H., 1983: Zonacion у Biomasa de la macrofauna bentonica en Bahia South, Archipelago de Palmer, Antartica. INACH Ser. Cient., 30: 27-38.

Zieliński К., 1990 (1991): Bottom macroalgae of Admiralty Bay (King George Island, South Shetland Islands, Anatarctica). Pol. Polar Res., 11: 95-131.

Addresses of the authors: prof, dr hab. Krzysztof Jażdżewski, dr Jacek Siciński, dr Piotr Presler — Laboratory of Polar Biology, Banacha 12-16, 90-237 Łódź, Poland.

UWAGI O FAUNIE DENNEJ ZATOKI ADMIRALICJI (SZETLANDY POŁUDNIOWE, ANTARKTYKA)

Streszczenie

Omówiono zasiedlenie przez organizmy zwierzęce dna Zatoki Admiralicji. Biomasa i liczebność zoobentosu są tu bardzo wysokie, sięgające kilku kg i kilkudziesięciu tysięcy osobników na 1 m2 . Największe bogactwo ilościowe zanotowano w płytkim sublitoralu (do ok. 30 m głębokości), podczas gdy najwyższe wartości biomasy stwierdzono w przedziale głębokości od 100 dO 200 m. Grupami zwierzęcymi dominującymi w zoobentosie pod względem liczebności były Bivalvia, Polychaeta i Amphipoda; pod względem biomasy dominowały Ascidiacea, Echinodermata, Bryozoa i Polychaeta.

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Tab.1. Total zoobenthos biomass (wet weight) in Admiralty Bay calculated for particular depth zones given by Rakusa-Suszczewski, Battke and Cisak (1992). Sampling unit - van Veen grab 0,09m2.

Depth zone

[m]

Mean biomass

[g*m-2]

95% confidence limits

[g*m-2]

Number of sampling

units [-]

Surface

[km2]

Total biomass

W 0-10 200 100-2601) 3 10,92 2184

10-50 420 130-500 11 25,92 10886

50-100 780 200-860 13 19,24 15007

100-150 1400 590-2140 7 8,00 11200

150-200 1250 300-2380 6 5,77 7213

200-250 880 390-1220 8 5,85 5148

250-300 490 170-910 6 6,65 3259

300-400 300 210-380 9 16,41 4923

400-500 340 140-590 6 14,56 4950

below 500 3402) 8,76 2978

Total 69 122,08 67748

1) Absolute range 2 ) no data available, the value of 400-500m zone is repeated.

Fig. 1. Relationship between zoobenthos biomass and depth for Admiralty Bay. Average values and 95% confidence limits are indicated