CALANUS IN NORTH NORWEGIAN FJORDS AND IN THE BARENTS SEA

Thc physical environment of a North Norwegian fjord and of the Atlantic and Arctic domains of the Barents Sea are described. The seasonal variation of primary production and biomass of the most important copepod species are described in order to contrast regional differences in the timing of the plankton cycles. Analysis of thc seasonal variation in the biomass of six different copepod species in Balsfjorden clearly demonstrate the importance of Calanus finmarchicus as a spring and early summer form, whereas Pseudocalanus acuspes, thc most important smaller form, reaches the highest biomass later during the productive season. In the Atlantic part of thc Barents Sea, C. finmarchicus is the dominant herbivorous form. The next most important species, Pseudocalanus sp. and M. longa. play a less important role here than in Balsfjorden. In the Arctic domain, the smaller copepod forms appear to have been replaced in trophodynamic terms by the youngest year-group (C-CIII) of C. glacialis, which prevails during the Arctic summer and autumn periods. The coupling between primary producers and Calanus on a seasonal basis is addressed through thc grazing and the vertical organisation of the plant-herbivore community. Thc productivity of these two Calanus species is considered in relation to the seasonal and inter-annual variation in climate; although different mechanisms are utilised, cold periods tend to lower Calanus productivity both in the Arctic and thc Atlantic domains of thc Barents Sea. Interannual variations in Calanus biomass and productivity arc discussed in the perspective of endemic and advective processes.