Zdenek 0URIŚ Wyprawy Geograficzne na Spitsbergen Department of Biology UMCS, Lublin, 1995 University of Ostrava Hladnovska 9 71-000 Ostrava, CZECH REPUBLIC

Jan Marcin WĘSŁAWSKI Institute of Oceanology Polish Academy of Sciences Powstańców Warszawy 55 81-967 Sopot, POLAND

A PRELIMINARY EXAMINATION OF ICE FLOES AT ISFJORDEN, SPITSBERGEN, ON A PRESENCE OF SYMPAGIC FAUNA

INTRODUCTION

Most of the Arctic Ocean is covered by sea-ice supporting a diverse assemblage of organisms. The animals inhabiting lower layer of the sea ice are frequently named sea ice fauna or sympagic fauna (Carey, 1985; Lonne, Gulliksen, 1991a). Golikov and Averintzev (1977) use a term 'cryopelagic biocoenosis' for a lower sea-ice surface community. The ice is in a continuous motion affecting its associates. The sympagic fauna and density of animals of sea-ice floes may deeply be reduced during the ice movement and melting. A small material of amphipod crustaceans associated with submerged surface of several sea ice floes was occasionally collected at Isfjorden, Spitsbergen, during the 9-th Arctic cruise of the Polish r/v Oceania. SCUBA diving was used for the observation and collection of sympagic crustaceans. This paper provides a contribution to the knowledge of two species of sympagic amphipod finds in the present material. The abbreviation TL used in the text, means the total body length of the crustaceans measured from the anterior margin of the head to the posterior margin of the telson.

MATERIAL, METHODS AND LOCALITIES

As a result, 39 specimens of two gammarid species (Crustacea: Amphipoda) were collected from submerged surfaces of ice floes. In addition, 5 other amphipods were examined collected from a fragment of fishing net flowing on the open sea free of ice.

227 A SCUBA-equipment and hand net with 1 mm mesh size were used for collection of sympagic fauna from ice-floes. Two dives were performed at Isfjorden for examining ice floes on a presence of sympagic fauna: 1. One large, about 20 m in diameter and 3 m in thickness, deeply melted ice floe was examined on July 25, 1995, at the middle of Gronfjorden, to the northwest of Barentsburg. Visibility of water 5-6 m. 19 amphipods collected. 2. Four deeply melted ice floes, from about 10 to 25 m in diameter and to 3.5 m in thickness, were investigated underwater at Adventfjorden, close to the new port of Longyearbyen, on July 27, 1995. Water transparency - about 3 m. 20 amphipods collected. All the floes examined belong to the same sea-ice field met by Oceania near Sorkap, the southernmost point of Spitsbergen, on July 15, 1995. The field covered an area from the southeastern Sorkapland at Storfjorden and along southern and western coasts to the middle between Hornsund and Bellsund on July 16, 1995. At the southwestern part of the area, the field extended to its maximal width reaching 15-20 nautical miles. The ice field wa s met by Oceania again at the southwestern part of the Isfjorden on July 25, 1995, reaching the eastern coast of the mouth of Gronfjorden. On July 27 the ice floes reached Adventfjorden.

SYSTEM ATI CS

Family CALLIOPIIDAE Apherusa glacialis (Hansen, 1867) Apherusa glacialis. - Yashnov, 1948: 303, 304, PI. 79, Fig. 5. - Golikov, Averintzev, 1977: 8-10, 52-53. - Lonne, Gulliksen, 1991a: 460-467; 1991b: 471-477. -Węsławski, 1991: 177, 248, Fig. 87. - Węsławski, Zajączkowski, 1992: 39. Material. R/V Oceania, Longyearbyen (port, new pier), Adventfjorden, Spitsbergen, 27 July 1995, vertical surface of sea-ice floe, 1-2 m deep, SCUBA, hand net, coll. Z. Duriś: 18 spms, TL 3.8-6.5 mm. Remarks. Small species, no longer than 7 mm in the present specimens, but reaching beyond 20 mm (Węsławski, 1991). Body semitransparent, greyish, with large dark chromatophores on lateral sides of thoracal and abdominal somites. Circumpolar, Arcitc species, occurs at the temperature below +1°C and salinity between 20 and 33 psu (Węsławski, 1991).

Family GAMMARIDAE Gammarus wilkitzkii (Birula) Gammarus wilkitzkii. - Yashnov, 1948: 313, 314, PI. 82, Fig. 4. - Golikov, Averintzev, 1977: 8, 10, 53.-Lonne, Gulliksen, 1991a:460-468; 1991b: 471-477;

228 1992: 10,21-26, 31.- Węsławski, 1991: 177, 278, Fig. 102; 1994: 145, 147, Fig. 2. - Węsławski, Zajączkowski, 1992: 39. - Węsławski et. al., 1993: 336, 337, Fig. 3. Material. R/V Oceania, 8 July 1995, open sea NW off Bear Island, 74°45'N 16°30'E, on flowing fragment of lost nylon fishing net, coll. Z. Duris: 5 spms, TL 13.5 -20.5 mm. R/V Oceania, 25 July 1995, Gronfjorden (NW off Barentsburg), Spitsbergen, lower surface of sea-ice floe, 1-3 m deep, SCUBA, hand net, coll. Z. Duriś: 19 spms, TL (6) 13-28 mm. R/V Oceania, 27 July 1995, Longyearbyen (new pier), Adventfjorden, Spitsbergen, lower surface of sea-ice floe, 1-3 m deep, SCUBA, hand net, coll. Z. Duris: 2 spms, TL 4.5 and 13 mm. Remarks. Large species reaching 48 mm body length (Yashnov, 1948). The present specimens smaller, up to 28 mm. Coloration transparent-yellowish with orange dots in joints of appendages. Typically observed are concentrations of these species under the perennial fast ice, with estimated densities up to 2000 ind/m2 (Węsławski, 1994). Lower concentrations were also observed during our dives under the ice floes examined, on their lower surfaces, mainly in deeper niches. Several specimens of these species occurred on a flowing fragment of a lost nylon fishing net at the open sea free of ice about 40 miles to NW from Bear Island. Only a single ice floes was observed to north of Bear Island, 74°45'N 19°E, one day after the catch of the flowing net mentioned. It may be supposed that the net had contacted for a time with rests of melting ice-floes and received some of their gammarid associates. According to the presence also of grown non-ice animals inside the involved net mass (mussels Mytilus edulis L., nudibranchs Dendronotus sp., polychates Nereis sp., hydroids, ...) the net probably has not been frozen to a winter pack ice. Circumpolar, High Arctic, cryopelagic species distributed mainly in ice covered areas (Węsławski, 1991; 1994).

DISCUSSION

A diverse group of animals inhabits the interface between ice and sea water, but only a limited number of species of macrofauna (ca. >5 mm) may be considered true sympagic (= sea-ice) forms. Amphipod crustaceans Apherusa glacialis (Hansen), Pseudalibrotus (= Onisimus) sp., and Gammarus wilkitzkii Birula, and the polar cod Boreogadus saida, are dominant sympagic species in open sea regions of Svalbard and the Barents Sea (Lonne, Gulliksen, 1991a, b; Lonne, 1992). The shallow water, coastal fast ice community is usually dominated by Pseudalibrotus litoralis (Kroyer) (Carey, 1985; Averintzev, 1992; Węsławski et al., 1993). A. glacialis dominates on a lower sea-ice surface,

229 community in shallow waters off Franz Joseph Land (Golikov, Averintzev, 1977). Only two of these species, A. glacialis and G. wilkitzkii, were found during the present research. Both of them are almost obligately associated with sea ice, the later mainly with the multi-year ice (Carey, 1985; Lonne, 1992). According to the thickness (> 1.8 m), the floes examined belong to the cathegory of the multi-year ice. The reduction of the sympagic fauna to two present species may be a result of a longer 'age' of the free floes originating from the Arctic sea-ice cover. An absence of gammarids P. litoralis, associated mainly with the shallow-water first-year ice, also shows the origin and age of the floes examined. The outflow of multiyear ice to the Barents Sea through the passages east of Svalbard, can temporarily be of considerable magnitude. The Arctic current and wind drove part of sea ice through Storfjorden to southern Spitsbergen, where the ice-field was reported by us, and then, following the north coastal current, to the north along western Spitsbergen as far as Isfjorden, where some floes were examined by us on the presence of sympagic fauna. The stage of the floes, deeply melted, also signaled a longer period of free ice. Although sympagic amphipods can as a rule hardly survive in open sea after fully melting the sea-ice, they occasionally may settle alternate substrate as reported above for G. wilkitzkii found on a flowing fragment of a lost fishing net. Moreover, this record also seems to be the southernmost location for the gammarid species. Similarly, the polar cod B. saida, usually occurring between sandwiched ice floes (Lonne, Gulliksen, 1989; Węsławski et al., 1990) may occasionally use rocky or stony bottom for hid ing (Duriś, 199 3), or may be found also in an association with jellyfish, as observed previously at Cyanea capillata L. ice-free Bellsund, western Spitsbergen (Duris, 1992).

ACKNOWLEDGEMENTS

The material was collected during the summer Arctic expedition to Spitsber- gen in 1995 on board the r/v Oceania (Polish Academy of Sciences, Gdańsk). The participation of one of us (Z. D.) in that expedition, and, as a result, also this study, were supported by Institute of Oceanology, Sopot, Poland, and also by several Czech institutions, firms and private persons, namely SEVEROMORA- VSKÄ ENERGETIKA a. s., TM-SERVIS Ostrava, J. BURSIK and ALVIN Ostrava, M. KAVAN Opava, and ALPISPORT Pribor. Our cordial thanks are extended to all the persons and representatives of the institutions named above.

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