Structure and dynamics of phytoplankton in the Oka River mouth at the beginning of the 21th century

Data on the species composition, abundance, and biomass of phytoplankton in the lower reaches of the Oka River are presented. The floristic and cenotic role of centric diatoms is shown. The dynamics of composition and abundance of some Centrophyceae species is analyzed using light and electron microscopy. The expansion of brackish-water diatoms has increased, but the eutrophic status of the stream is maintained against the background of drastic changes in abiotic conditions in the river at the beginning of the 21th century.