Phytoplankton as an idicator of the ecological state of the Mana River (Krasnoyarsk Region)

According to the results of phytoplankton studies in the Mana River (Krasnoyarsk Region) in 2021–2024, its species composition was supplemented, as well as its taxonomic structure, dominant algae complexes, abundance and biomass, and biodiversity indices were established. 159 species and intraspecific taxa of algae from 7 divisions were identified. It was found that the basis of the species richness (67.92%) is created by diatoms. The dominant phytoplankton complex is formed by randomly planktonic diatom species, heterocyst-free cyanoprokaryotes, and small cell green and yellow-green algae. The biodiversity indices of the phytoplankton communities indicate a low level of species diversity and an average complexity of their structure. The trophic status of the river mainly corresponds to the oligotrophic category of waters, with the transition to mesotrophic in 2021. The water quality ranges from class 1 "extremely clean" to class 3 "satisfactory purity". The ecological state of the Mana River is generally assessed as satisfactory with the presence of some negative processes caused by increased anthropogenic impact.