Hydrobiological characteristics of the Volga river in 2021-2023

The section of the Volga River below the Volga Hydroelectric Station dam within the Volgograd region is experiencing the influence of changes in anthropogenic hydrological processes. Changes in natural hydrological processes influence the Volga below the Volga GES within the Volgogr ad region. Given the peculiarities of the hydrological regime, it is relevant to analyze the state of phytoplankton, zooplankton, and zoobenthos organisms, which are sensitive indicators of the state of water bodies and respond to changes. The article presents the results of hydrobiological studies of 2021-2023 on the river section of the Volga River within the boundaries of the Volgograd region. Hydrobiological sampling was carried out in each of the three seasons (spring, summer, and autumn) once in three sections (Priplotinny section, Kirov section, and Raigorod section). The grid of stations, consisting of 9 sampling points, was located in such a way as to cover all ecological zones of the reservoir: open coastal and deep water, which are characterized by a variety of bottom biotopes: sil ty sand, sand mixed with shells, and rocky. During the research period, 243 samples were taken, of which 81 were phytoplankton, 81 were zooplankton, and 81 were zoobenthos. The qualitative and quantitative characteristics of hydrobiocenoses were determined, on the basis of which the saprobity index was calculated, and the quality class of water and bottom sediments was determined. As a result of assessing the water quality based on the development of phyto- and zooplankton communities, the studied sectionsof the watercourse belong to water class III, which corresponds to the a-mesosaprobic zone, “moderately polluted”, and benthic communities to water class IV, “polluted”.