The zooplankton community structure was studied in the Svalbard area at three shelf stations: Billefjorden, Kongsfjorden and Hinlopen (Spitsbergen shelf area), and at two open water stations: Ice West and Ice East (north of Spitsbergen, in the Arctic Ocean). Two different plankton nets – WP-2 and WP-3 – were used to collect a size range of zooplankton. The Bray-Curtis similarity analysis showed differences between sampling stations based on total zooplankton abundance, species composition, and comparison of Calanus spp. development. Total abundance was the highest in Kongsfjorden and Hinlopen. The small omnivorous copepod Oithona similis Claus, 1863 was the dominating species at all localities and the Atlantic copepod Calanus finmarchicus (Gunnerus, 1765) was found at all stations. Calanus spp. development was delayed at the ice stations when compared to the shelf stations. Results are discussed in relation to differences in environmental factors among stations.

The population structures of Calanus finmarchicus, C.glacialis and C.hyperboreus were investigated in the recurrent polynya of the North Waters (NOW) in Baffin Bay during April –July 1998. Species were determined from samples collected by plankton nets of 300 ľm and 200 ľm mesh size. The highest concentration of all three species was found at the centre of study the area. C.hyperboreus was the most abundant species (44.54 ind.m –3).C.glacialis was recorded up to 27.14 ind.m –3, C.finmarchicus up to 5.63 ind.m –3 .C.finmarchicus was reproducing in the northern end of Baffin Bay.The life cycle for C.glacialis was estimated at 2 years,and that of C.hyperboreus to last at least 4 years.