Arctic Macroplankton Krill Fjords

This paper presents the results of 15 zooplankton tows collected with a Tucker Trawl (1 m2 opening, net of 2 mm mesh size) in Kongsfjorden (79◦N), Svalbard archipelago. The hydroacoustic survey revealed clear differences between the plankton concentrations in the outer and inner fjord basins. Plankton concentrations and fish were observed in the outer fjord, while uniformly scattered objects were detected in the inner basin. The macroplankton community was dominated by Euphausiacea (Thysanoessa inermis, Thysanoessa rashii), Amphipoda (Themisto libellula) and Pteropoda (Limacina helicina). Other taxa were of minor numerical importance. The macroplankton abundance reached 3300 indiv. 100−1 m−3 with a maximum biomass of 100 g wet weight 100−1 m−3 (over 440 kJ 100−1 m−3). L. helicina was advected into the fjord with surface waters, and was found in large * The present study is part of BIODAFF (The Biodiversity and Fluxes in Arctic Glaciated Fjords Project), funded in part by the Polish State Committee for Scientific Research, grant PO4–95–09. 58 J.M. Węsławski, G. Pedersen, S. F. Petersen, K. Poraziński abundance (1000 indiv. 100−1 m−3) in the subsurface layers of the inner basin. Euphausids were present in small numbers at the entrance to the fjord, but were found to be very abundant (600 indiv. 100−1 m−3) at the innermost stations, especially in the surface water layer. The estuarine circulation driven by the glacial meltwater discharge is believed to cause the entrapment of zooplankton in the inner fjord basin.