Taxonomic composition and ecological features of phytoplankton in Lake Ostrovito (Pskov region)

Abstract

Lake Ostrovito is located in the Pskov region and belongs to the basin of the Belyavitsa River, a tributary of the Velikaya River. The lake covers an area of 1.1 km2, with a maximum depth of 16.0 m and presents an important recreational and fishery facility in the Pskov region, constantly experiencing anthropogenic impact due to the close proximity of villages and recreation centers. Monitoring works have been conducted to assess the ecological state of this lake. The aim of the work was to study the species richness, quantitative characteristics and ecological features of phytoplankton of Lake Ostrovito in the autumn period of 2020. The study identified 65 species and intraspecific phytoplankton taxa from 7 phylums. The basis of the floral complex was made up of representatives of the departments Chlorophyta, Bacillariophyta and Cyanobacteria. The analysis of the floral similarity of phytoplankton communities of the studied lake stations using the Sierensen-Chekanovsky index showed their average degree of similarity (from 43.3 to 58.1%). The values of the abundance of autumn phytoplankton varied from 127 thousand cells/l to 488 thousand cells/l (the average number is about 290 thousand cells/l). Phytoplankton biomass ranged from 68.7-110 micrograms/l (average biomass – 96.1 micrograms/l). The average value of the Milius trophic index was 21.1, which indicates an oligotrophic type of reservoir. According to ecological and geographical analysis, freshwater widespread planktonic forms of microalgae predominated in Lake Ostrovito, preferring slightly alkaline waters and indicating moderate pollution of the reservoir.