Plankton and Benthos of the Svir River Connecting the Largest Lakes in Europe

In May, August, and September 2023, studies of phytoplankton, zooplankton, and macrozoobenthos were conducted at seven stations of the Svir River. A total of 63 hydrobiological samples were taken. In general, the plankton and benthos of Svir River are clinical in nature. Two species of relict crustaceans have been found: Limnocalanus macrurus and Pallaseopsis quadrispinosa. An invasive species of amphipod, Gmelinoides fasciatus, is also found throughout the river. The main factors determining the development of different groups of hydrobionts of the river are changes in its hydrological regime, the influence of runoff from Lake Onega, and navigation. Along the entire length of the river, according to all studied groups of hydrobionts, the river belongs to the β-mesosaprobic zone, and in summer it belongs to the oligosaprobic zone, according to zooplankton. In the dammed areas along the macrozoobenthos, it falls within the α-mesosaprobic zone.