Zooplankton was investigated at fixed site in 24 hours in Kongsfjorden, a glacial fjord situated on the west coast of Spitsbergen (Svalbard) (79°N, 12°E), in order to unveil the level of diurnal variability in community composition and abundance. Parallel to zooplankton study water temperature and salinity were measured while information on local tides and winds was obtained from external sources. Observed changes did not exceed the range of variability regarded intrinsic, resulting from the nature of plankton. Because of this low variability we are of the opinion that the data presented can be regarded a valid measure of the natural heterogeneity of zooplankton communities in hydrologically dynamic Arctic coastal waters in summer. The observed changes in zooplankton were primarily induced by the complex dynamics of the fjord’s water masses. In spite of importance of tidal forcing, the variability in zooplankton did not demonstrate similar temporal fluctuations due to modification of the water movement by other irregular forces (local wind). Also, we have not found any indication of diel vertical migration in coastal water in the Arctic under the condition of midnight sun.

Chlorophyll α, phytoplankton, suspensions and zooplankton beneath the fast ice have been studied in Spitsbergen fjords (Hornsund, Bellsund, Sassenfjord, Gronfjord and Kongsfjord) in 1982, 1984/85,1987 and 1988. Observations on ice associated Polar cod and wildlife have been collected simultaneously. There were no typical sympagic communities observed at the West Spitsbergen fast ice. Exception was spring 1982 and 1988 when drifting ice from Barents Sea contributed to the fjords fauna. Fast ice on the investigated fjords was poor in adjacent zooplankton (biomass below 0.06 g/m3). Ice phytoplankton reflects the autumn situation and no specific communities of algae have been found. Chlorophyll α amount and organic sedimentation from ice and from the adjacent water were very similar (0.4 to 1.7 mg/m3 chlorophyll and 8 to 10 g d.w./m2/day sedimenling matter). The diet of Polar cod reflected the food items occurrence, Calanus has been the most common food. N o specific concentration of seabirds have been observed at fjords ice.

Two West Spitsbergen fiords, Hornsund (77°N) and Kongsfjorden (79°N) were compared with respect to their hydrology and zooplankton occurrence on the base of two summer surveys made in 1987 and 1988. Both fiords were found to be influenced by four types of masses: Atlantic Waters, Intermediate Atlantic Waters, Local Waters and Brackish Surface Waters, Intermediate Atlantic Waters, Local Waters and Brackish Surface Waters. The amount of fresh water in both fiords reached up to 10% of water volume of the uppermost water layers. Hornsund in August 1987 was richer in mesozooplankton biomass than Kongsfjorden in 1988. Estimated energie value of pelagic prey of marine birds was 180-500 KJ/100 m3 in Hornsund, and 130-200 in Kongsfjorden. Two major plankton communities were found in both fiords: Pseudocalanus community in the inner fiord basins and Calanus dominated community in the outer areas of the fiords. Plankton occurrence in fiords was not linked directly with the temperature — salinity patterns but rather with dynamic phenomena like upwellings and wind drift of surface waters.

The food and foraging strategy of fifteen species of seabirds and sea mammals from two high Arctic fjords were analysed. One of the fjords, Kongsfjord, is strongly influenced by warm waters from the Atlantic , while Hornsund is of a more Arctic character. Prey species in the Atlantic waters were more diverse (82 species and 16 functional groups) compared to those of Arctic waters (67 prey species and 14 functional groups). The consumption of top predators from Hornsund in the peak season of July was estimated at 2.86*106 MJ, while that in Kongsfjord was 1.35*106 MJ. For the analysed function of the ecosystem (the transfer of energy to the top trophic levels) the specific character of prey species is of key importance and not the diversity, abundance or biomass per se. Lower species diversity and biomass in Arctic waters is compensated for by the occurrence of larger individuals of these species, which permits top predators to prey directly on lower trophic levels.

Zooplankton community composition, abundance and biomass from two polar localities – Kongsfjorden (Arctic) and Admiralty Bay (Antarctic) is compared. The community composition of zooplankton in both polar regions included similar taxonomic groups and the diversity at the species level was similar. Even though the overall species composition was different, some species were common for both ecosystems, for example Oithona similis, Microcalanus pygmaeus or Eukrohnia hamata. The abundance and biomass of the main zooplankton components (Copepoda) differed greatly between the two ecosystems, both being of an order of magnitude higher in Kongsfjorden than in Admiralty Bay. Kongsfjorden is situated at the border of two regions what induces high productivity with copepods playing an important role, and there is also a strong advection into the fjord. Admiralty Bay is adjacent to the homogenous Antarctic oceanic ecosystem; some advection into the bay occurs as an effect of tide and wind driven processes. Antarctic krill, which was not included in the present study, occupies most of the primary consumers niche and replaces copepods at the second trophic level.