Zooplankton of the White Sea: Features of the Composition and Structure, Seasonal Dynamics, and the Contribution to the Formation of Matter Fluxes

The composition, seasonal dynamics, and regional variations in the distribution of zooplankton are studied in the shallow-water coastal and deep-water open areas of the White Sea. In the shallow-water areas, seasonal observations were carried out in the period between 1960 and 1997 from spring to autumn and during several annual cycles. In the deep-water areas, the data was collected in the course of several plankton surveys from early spring to late autumn during the period from 1998 to 2001. The available data shows that the boreal, Arctic, and arctic–boreal taxa comprise most of the zooplankton stock in this subarctic sea. The boreal taxa, together with meroplankton, represent a temporal component of the zooplankton and they dominate the stock of the shallow-water regions during the warm season. The variability of the seasonal biomass is well pronounced in the shallow-water areas. The difference between the minimum winter biomass and the summer maximum is 10to 20-fold. In contrast, in the deep-water areas, in the period from 1998 to 1999, only a twofold difference was observed from spring to fall. In the deep-water areas, the seasonal variations in the vertical and horizontal distribution of zooplankton are well pronounced. They are identified by a few “key” psychrophil (Arctic and arctic–boreal) species; namely, by the copepods Calanus glacialis, Metridia longa, Pseudocalanus minutus , and by the chaetognath Sagitta elegans . These species undergo clearly pronounced seasonal vertical migrations, which result in a dramatic vertical replacement of the biomass within the water column over the course of the year. Regional differences in the biomass distribution between different areas and bays of the White Sea are described. These are closely related to the hydrophysical regime, the circulation pattern, and the bottom topography. Possible ways of assessing the contribution of zooplankton to the vertical carbon flux in the White Sea are discussed.