The article deals with spatial and temporal dynamics of specifics of phytoplankton in the Hnylopiat River. For the last 10 years, the share of Euglenophyta in the phytoplankton species diversity has increased, that might be regarded as the algal communities’ natural response to organic pollution. On the contrary, Bacillariophyta have reduced their share and the absolute number of species. The quantitative values of the phytoplankton have grown up, mainly due to blue-green algae mass vegetation. We have also recorded a decrease in the planktonic algal communities’ evenness, that was caused by cultural eutrophication, and a rise in the saprobity index, that is the evidence of water qua­lity aggravation. Planktonic algal communities are distinguished by well-marked discrete pattern along the river profile under the impact of human factors, that consists in the increase of number of cells owing to mass vegetation of Cyanoprokaryota in the regulated sections; reduction in the quantitative values of algae vegetation and the rise in the share of Euglenophyta in the species composition and biomass of algal communities. Besides, water quality aggravation in the section was affected by the wastewater treatment facilities of Berdychiv city. An increase in number of forms typical for soil and land substrata in the river section located downstream of the wastewater treatment facilities and are regulated by the pond.