S108 Oceanology, Vol. 43, Suppl. 1, 2003, pp. S108–S122. Original Russian Text Copyright © 2003 by Pertsova, Kosobokova. English Translation Copyright © 2003 by åAIK “Nauka /Interperiodica” (Russia). INTRODUCTION The studies of White Sea zooplankton have more than a century-old history. During this period, for dif- ferent areas of the sea distinct in their hydrological con- ditions and bottom topography, the faunistic composi- tion of zooplankton has been studied and the factors which determine it have been described [36]. Thanks to the long-standing observations carried out in the coastal areas of Kandalaksha Bay of the White Sea, by staff members of the Pertsov White Sea Biological Sta- tion affiliated with Moscow State University and the White Sea Biological Station affiliated with the Zoo- logical Institute of the Russian Academy of Sciences, the annual dynamics of the abundance and biomass of zooplankton and the ecology and life cycles of mass species, as well as their vertical migrations, have been comprehensively examined [36; 51, 58 and references within them]. Over almost a half-century period, a great amount of data on the interannual biomass variations of Kandalaksha Bay has been accumulated [34]. Up to the present day, the majority of systematic zooplankton observations have been carried out pre- cisely in Kandalaksha Bay. The remaining areas have been examined casually, and often using incomparable methods [34]. Only in recent years have several com- plex expeditions been performed. Observations were repeatedly carried out using standard methods against the background of hydrophysical, hydrochemical, and geochemical measurements over a vast water area in different seasons [23, 59]. These studies have brought many new views of the structure and seasonal dynamics of the plankton community from the least understood deep-water areas [34, 59], its interaction with the com- munities from the coastal areas [57], and the biological processes in the zones of influence of major and minor rivers [23, 35], as well as at the boundary between the White Sea Basin and the Gorlo [23, 54]. This study is aimed at the generalization of the new data regarding the White Sea plankton community that has been acquired during recent years, the description of quantitative regularities in the zooplankton distribu- tion over the water area of the sea, and the discussion of the role of zooplankton in the formation of vertical car- bon fluxes and sedimentation. MARINE BIOLOGY Zooplankton of the White Sea: Features of the Composition and Structure, Seasonal Dynamics, and the Contribution to the Formation of Matter Fluxes N. M. Pertsova 1 and K. N. Kosobokova 2 1 Biological Faculty, Moscow State University, Moscow, Russia 2 Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia Received March 12, 2003 Abstract—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 pro- nounced in the shallow-water areas. The difference between the minimum winter biomass and the summer max- imum is 10- to 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.