Structural indicators and toxic species of cyanobacteria of Pskov Lake

The cyanobacterial communities of Lake Pskov were studied in several seasons of 2021, and a comparison was made with the data of earlier studies. Data on the taxonomic composition and quantitative characteristics of cyanobacteria have been obtained, and some species toxic to living organisms are shown. 196 species taxa of phytoplankton in total were recorded at four permanent stations of the lake, 15.8% of which were cyanobacteria. The cyanobacterial communities were most similar in terms of the specific composition in summer and autumn. Some quantitative indicators of cyanobacteria, such as their abundance and biomass, were minimal and maximal in spring and summer–autumn, respectively. Toxic and potentially toxic species belonging to the genera Anabaena, Aphanizomenon, Lyngbya, Microcystis, Nodularia, and Nostoc were present among the detected cyanobacteria in each of the studied seasons of the year. The total contribution of representatives of these genera to the total abundance of phytoplankton varied from 4.0% in spring to 65.0% in autumn. In summer, the share of cyanobacteria from the above genera in the total number of microalgae accounted for ~40.0%. The greatest role was noted for the algae Microcystis aeruginosa (Kützing) Kützing, which causes “blooming” of reservoirs and also produces the toxin microcystin with hepatotoxicity. Any study of Lake Pskov requires constant monitoring of the content of cyanotoxins, especially in autumn, when the maximum biomass content of cyanobacteria, including toxic species, is observed, which may lead to serious consequences.