Species Composition, Seasonal Dynamics and Distribution of Phytoplankton of the Zaporizke Reservoir

Species composition, seasonal dynamics and distribution of phytoplankton were researched to characterize temporal dynamics and horizontal distribution of phytoplankton and to indicate the ecological status of the sites in the Zaporizke reservoir. During 2015 - 2016 a seasonal dynamics of species composition and quantitative characteristics of phytoplankton have been studied near Monastyrsky island in upper part of the reservoir both in surface and bottom layers in conjunction with water temperature measurement. At early September 2016 phytoplankton sampling was performed at different sites of the Zaporizke reservoir including the sites undergone to sewage impact. During phytoplankton seasonal dynamics diatom bloom was reported in March and early April and algae biomass was higher in the bottom layer with a gradual decrease in the direction of the surface layer. From July to October the apparent dominance of blue-green algae took place with a clear concentration in the surface layer. Domination of the species Microcystis aeruginosa determined phytoplankton distribution along the reservoir at the beginning of September. Despite the high resistance to the effects of toxic substances the level of Microcystis aeruginosa (Kützing) Kützing 1846 development decreased at the sites of direct sewage impact. At 100m below the sewages sites degree of phytoplankton development increased mainly due to increase of blue-green algae abundance. Indexes of phytoplankton showed the best ecological state at the site «near Kodaki water draw-off» and the worst ecological state at the sites of direct sewage impact. The results obtained are important to indicate ecological state of the sites in the Zaporizke reservoir.