Dynamics and Relationship between Plankton Organisms in the Littoral Zone of a Large Plain Reservoir at the Beginning of the Vegetation Season

The dynamics and relationship between planktonic algae, bacteria, protozoa, invertebrates, and viruses were studied at different sites in shallow littoral zones of the Rybinsk Reservoir (Upper Volga) in April–June. The features of seasonal succession of different components of the littoral plankton community have been identified. The spring peak in the development of phytoplankton, caused by diatoms and cryptophyte algae, is weakly pronounced in shallow littoral waters. An increase in the number of bacteria and development of protozoa and zooplankton in the littoral occurs earlier than in the open part of the reservoir. Consequently, the clear-water phase starts earlier and has a shorter duration. An important role in the nutrition of the littoral zooplankton, in addition to phytoplankton, is played by heterotrophic protozoa and bacteria developing through the use of both auto- and allochthonous organic substances.