Phytoplankton Characteristics in Various Ecosystems of the Dnieper River: Quantitative Indices, Dominant Complex, Response of Algae to the Influence of Certain Ecological Factors, and Water Quality

In summertime, phytoplankton of the Kyiv Reservoir and the Dnieper River estuary was characterized by high cell numbers and biomass typical to highly trophic water bodies. At the same time, in the estuary the numbers and biomass of phytoplankton (in particular those of Cyanobacteria) were almost one order of magnitude higher than those registered in the reservoir, which is likely conditioned by a warmer climate of the estuary region. Not only water temperature, but also hydrological and hydrochemical factors influenced long-term dynamics of Cyanobacteria in the Kyiv Reservoir. In the estuary, long-term dynamics of Cyanobacteria development were conditioned mainly by temperature regime. The increase in mineralization of the Dnieper River water results in the spread of brackish-water and marine species of algae. In this case, in the estuary the intensity of this process is essentially higher than that in the reservoir. Water quality both in the reservoir and in the estuary is characterized as «moderately contaminated waters», which is typical to many lotic and lentic ecosystems of Ukraine and the European Union. The obtained data can be used as background for further assessment of negative consequences of the military actions of the Russian Federation for the Dnieper ecosystems of Ukraine.