Content Composition and Dynamics of Photosynthetic Pigments in the Reservoirs of the Kalmius River of the Donetsk People’s Republic

The paper presents data on the content, composition, and interannual and seasonal dynamics of photosynthetic pigments in the Lower Kalmius and Starobeshevo reservoirs of the Kalmius River in the Donetsk People’s Republic. The average chlorophyll a content in the reservoirs ranged from 54.24 ± 1.4 to 106.47 ± 1.5 µg/L. The Lower Kalmius Reservoir was characterized by higher values of photosynthetic pigment concentration with lower phytoplankton biodiversity. The presence of a constant dominant group and increased concentrations of nutrients characterize the reservoir ecosystem as unstable. The summer bloom of cyanobacteria determines high chlorophyll a concentrations. The increase in the absolute and relative number of cyanobacteria indicates the transition to the eutrophic type of the reservoir. The Starobeshevo Reservoir was characterized by a wide variability of chlorophyll a values with no single peak character of phytoplankton development. Interannual changes in chlorophyll a depend indirectly on the temperature factor and largely on the variation of concentrations and biogenic elements. The annual increase in temperature leads to a prolongation of the period of maximum chlorophyll a concentrations. In general, the ecosystem of the Starobeshevo and Lower Kalmius reservoirs is coping with anthropogenic impacts.