The First Information about the Phytoplankton and Ecological State of the Vasyugan River (Tomsk Oblast).

The species composition, taxonomic structure, dominant complex, abundance and biomass, and indices of phytoplankton biodiversity have been determined for the first time using the results of studies of the Vasyugan River in July 2019 and 2021. We have identified 166 species and intraspecies taxa of algae from eight divisions, and green algae (the division Chlorophyta) form the basis of species richness. The dominant phytoplankton complex includes centric diatoms, green algae, and non-heterocyst cyanoprokaryotes. Biodiversity indices reflect high species richness and close to moderate complexity and evenness of the phytoplanktocenosis structure. The trophic status of the river corresponds to the eutrophic category of waters, and the water quality ranges from class 3 (satisfactory purity) to class 4 (polluted). [ABSTRACT FROM AUTHOR]