Current State of Phytoplankton in the Volga, Kama, Don and Volga-Don Canal Reservoirs (Summer 2015–2018) under Conditions of the Changing Climate and Continuing Eutrophy

In August 2015–2018, the phytoplankton of 15 reservoirs of the Volga, Kama, Don rivers, Volga-Don Canal, and the unregulated part of the Lower Volga was studied. A decrease in the species richness, diversity, cell size, total phytoplankton and phytoflagellates biomass in the Volga-Kama cascade was observed from the upper to the lower reaches of the regulated rivers. This reflected the zonation and hydrological continuity. The proportion of biomass of non-heterocystous cyanobacteria in the reservoirs increased with increasing salinity of their waters. The trophic state of the reservoirs was assessed based on the phytoplankton biomass value.