Trophic State of Benthal in a Large Channel Reservoir in Relation to the Structure of Bottom Sediments

In the summer of 2015–2023, pigments in BSs were studied as indicators of the trophic state of benthal in the large channel Saratov Reservoir, which stands out in the cascade of Volga River reservoirs for its high rates of water exchange and sedimentation. In the reservoir, the areas of coarse-grained sediments exceed those of fine-grained sediments by 4.2 times. The average content of chlorophyll a with pheopigments in the upper 5-cm sediment layer (12.4 ± 1.6 μg/g DS), calculated considering the areas of BSs of different types, corresponds to the oligotrophic category. The most common values of pigment concentrations vary within the oligotrophic and mesotrophic categories. Concentrations of organic matter and pigments per 1 g of organic matter of BSs in Saratov Reservoir were minimal for the Volga cascade.