Role of Picoplankton in Phytoplankton Communities of Freshwater Ecosystems (an Overview)

During a year, the contribution of autotrophic picoplankton to the total numbers of cells and organisms of phytoplankton varies over a wide range. It accounts for 2-98% and 24-96%, respectively. The contribution of autotrophic picoplankton to the total numbers of phytoplankton during November - April is higher than that registered during the vegetation season (from May till October). The contribution of autotrophic picoplankton to the total biomass of phytoplankton, provided that the cell mass is 2 Ч10-9 mg, is not high (0.4-4.2%). From November till April, it is somewhat higher (3.8-24.7%). Unlike the absolute values of development of autotrophic picoplankton, its relative values do not correlate with the trophic level of the studied water bodies.