LAUSR

Abstract New data on the chlorophyll a (Chl a ) content in the water of the Volga River reservoirs are presented. In years with different temperature regimes (2017 and 2018), the content of Chl a varied from minimal 2.2–13.8 to maximal 7.6–50.5 and 25.8–104 µg/L, respectively. As before, the Chl a concentration in the Volga cascade decreases from the upstream reservoirs to downstream ones; the maximum is recorded in highly eutrophic Shosha reach of the Ivankovo Reservoir and in the estuarine section of the Oka River in the Cheboksary Reservoir; and the local increase in Chl a is also recorded in tributaries and their mouth areas, protected shallow areas, and near-dam zones. The mean Chl a concentrations characterize the Ivankovo, Uglich, and Cheboksary reservoirs as eutrophic and the Saratov and Volgograd reservoirs as mesotrophic; the trophic status of the Rybinsk, Gorky, and Kuibyshev reservoirs varies from mesotrophic to moderately eutrophic and eutrophic.