Analysis of the structure of phytoplankton communities in the ecological monitoring of Lake Zaozernoe (Russia)

In this work, the taxonomic composition, biodiversity, abundance, biomass, ecological features of planktonic algae and water quality in Lake Zaozernoye of the Pskov Region were studied a year after the territory was recognized as a natural monument. A twofold increase in the species richness of plankton was revealed, a two-fold decrease in representatives of the Euglenozoa phylum and a 40% decrease in representatives of Cyanobacteria. 145 phytoplankton taxa ranked below the genus from 8 phylums have been identified: Bacillariophyta (50 species taxa), Chlorophyta (36), Ochrophyta (18), Cyanobacteria (12), Euglenozoa (12), Miozoa (8), Cryptophyta (5) and Charophyta (4). The biomass was dominated by diatoms and cryptophytic algae. Toxic cyanobacteria species Aphanocapsa delicatissima and Aphanothece sp. have been identified among the dominant species in terms of numbers. 2 rare species of algae have been identified for reservoirs in the Northwestern region – Anabaena sphaerica Bornet Flahault (Cyanobacteria) and Phacus monilatus (A. Stokes) Lemmerman (Euglenozoa). The analysis of species diversity using the Sierensen–Chekanovsky, Shannon, Simpson, and Margalef diversity indices revealed changes in the structure of the plankton community in different areas of the lake. The species composition of Zaozernoye is compared with the lakes closest to it.