Структурно-функциональные характеристики фитопланктона озера Вендюрского, испытывающего влияние форелевого хозяйства

Abstract

The paper presents the results of a study of the phytoplankton of small Lake Vendyurskoe (south of Karelia) in the spring ice period, in summer and autumn seasons of 2020. The dynamics of quantitative and structural indices of lake algae during the trout farm operation is considered in comparison with the indices of previous years. For the studied seasons of 2020 there were identified 122 taxa of algal flora belonging to 8 divisions. The structure of algocenoses can be characterized by rich species diversity and quantitative development as diatom green structure with golden algae insertions. In autumn the representatives of cyanobacteria were encountered en masse in some areas. Phytoplankton abundance in the spring ice period varied within 612 thousand cells/l - 2188 thousand cells/l, the biomass reached 2.9 mg/l with a minimum value of 0.1 mg/l. Phytoplankton abundance for the studied summer period of 2020 averaged 2216±796 thousand cells/l with a maximum value of 3986 thousand cells/l, the average biomass in the lake did not ex-ceed 1.325±0.504 mg/l. Phytoplankton abundance in autumn averaged 4934±1665 thousand cells/l with a maximum value of 7832 thousand cells/l; biomass averaged 5.8±1.5 mg/l with a maximum value of 7.9 mg/l. According to the eco-logical and geographical characteristics, most representatives of the algal flora found in the lake are widespread freshwater organisms belonging to the planktonic flora and preferring a neutral reaction of the environment. The Shannon index increased from 2.8 in the center of the lake to 3.3 in the trout farming area, which indicates good species diversity. The Sorensen index of 0.8 revealed the homogeneity between phytoplankton communities in different areas of the lake. Most of the identified types of saprobity indices belong to the representatives of the 
 β-mesosaprobic and oligo-beta-mesosaprobic zones (up to 78% of the total number of identified indicator species). The saprobity index corresponded to the 2nd class of water purity (pure, α-oligosaprobic), which is due to the species composition of the dominant phytoplankton complex, however, the biomass indicates that the lake belongs to the 3rd class of water purity (satisfactorily clean, β-mesosaprobic).