Modern Trophic State of the Benthic Zone in the Ivankovo and Uglich Reservoirs According to the Content of Sedimentary Pigments

New data on the content of chlorophyll a with pheopigments (Chl + Ph) in bottom sediments (BSs) of the Ivankovo and Uglich reservoirs of the Upper Volga (Russia) obtained in 2019 are given. The relationships between pigment concentrations and characteristics of bottom sediments and depth are analyzed. It is established that at present the average concentration of Chl + Ph is 156 μg/g dry weight in the Ivankovo and 105 μg/g dry weight in the Uglich reservoirs, which exceeds the values obtained 20 years ago (126 and 79 μg/g dry weight, respectively). An increase in the concentration of sedimentary pigments was recorded mainly in the zones of silt accumulation. The weighted average content of sedimentary pigments calculated based on the areas of different sediments makes it possible to estimate the trophic state of the benthic zone in the Ivankovo Reservoir (125 μg/g dry weight) as the initial stage of hypertrophy and in the Uglich Reservoir (52.8 μg/g dry weight) as the final stage of mesotrophy. The trophic state of the benthic zone in both water bodies corresponds to the eutrophic status of the pelagic zone.