New data on chlorophyll content at standard stations in the Rybinsk reservoir, that continue series of long-term observations, were obtained in May–October 2015–2019. A fluorescent method is used in this study which makes it possible to determine the total amount of chlorophyll (ΣChl) by its content in cyanoprokaryotes, di-atoms, and green algae (ChlCyan, ChlBac, ChlChl, respectively). These taxa are the main contributors to ƩChl which show interannual and seasonal variation. In different

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... the average content of ChlBac makes 2.4–6.6 μg/L or 24–50% of the ΣChl pool, ChlCyan – 3.1–10.9 μg/L (50–70%), ChlChl – 0.3–1.2 μg/L (3–12%). The distribution of ChlBac in the water column is generally uniform while the amount of ChlCyan decreases with depth. With the average ΣChl content for the growing season 14.8±1.0, 13.0±1.3, 7.8±0.6, 13.6±1.6, and 11.9±1.0 μg/L in 2015–2019, the trophic status of the reservoir varied from moderately eutrophic to mesotrophic.