SPECIFIC FEATURES OF PHYTOPLANKTON DEVELOPING IN VOLGA RIVER GENERAL CHANNEL
Studies of the qualitative diversity and quantitative composition of phytoplankton of the Volga river general channel were carried out at eight stations (Dubovka village, Kamenny Yar village, Staritsa village, Solenoe Zaymishche village, Tsagan-Aman village, Enotaevka village, Seroglazovka village, Zamyany village) in June and August 2019-2021. During the study period there were collected and processed 56 samples. In the course of studying the taxonomic composition of microalgae there were recorded 200 species in three years. The predominant group in the phytoplankton species composition was diatoms, which accounted for more than 50% of the total amount. Phytocenosis of the Volga river was supplemented by green algae and cyanobacteria. The other groups of algae (Dinophyta, Euglenophyta, Chrysophyta) were of the least importance for overall development. The abundance and biomass of phytoplankton of the Volga River root bed have been changing abruptly for three years, the highest indicators were registered in 2020 (abundance = 550.06 million cells/m3, biomass = 1144.010 mg/m3). Quantitative indicators of phytocenosis unevenly developed yearly from June to August. The abundance increased by August in 2019 and 2021 and decreased in 2020. Algocenosis biomass de-creased by the end of summer in 2019 and 2020 and increased in 2021. Quantitative changes of algae are given. There was determined predominance of diatoms. Cyanobacteria and green algae were important mainly due to their growing abundance. The study of river phytoplankton helped reveal the stations with the greatest development of microalgae: the villages of Staritsa, Seroglazovka, Solenoe Zaymishche and Zamyany.