Epiphyton structure peculiarities in the regions of Lake Pskovsko-Chudskoe with various degree of anthropogenic pollution

Abstract

The paper presents the results of studies on the structural characteristics of epiphyton communities in Lake Pskovsko-Chudskoe (Lake Peipsi), carried out in July 2013 on 13 stations (Russian part). The purpose of the study was to identify changes in the epiphyton community caused by various degrees of anthropogenic pollution in different areas of the lake. In general, the level of pollution of Lake Pskovsko-Chudskoe is largely determined by the processes occurring in its catchment area and, above all, pollution of its basin. The main sources of pollution (insufficiently treated waste water) are located at the mouths of the Velikaya River and the Gdovka River. In total 279 taxa of algae with rank below genus were identified within epiphyton. The basis of systematic list was made up of three divisions: Bacillariophyta, Chlorophyta and Cyanoprokaryota. Number of taxa in the studied stations varied from 46 to 111. The structure of the biomass at all stations was presented by Bacillariophyta and Chlorophyta. Values of attached algae total biomass ranged widely: from 0.5 to 6.8 g/m2. The Shannon diversity index values at most stations were high indicating considerable diversity of epiphyton communities. Index declined sharply in areas with highest level of pollution. Values of saprobic index were within β-mesosaprobic zone range, which corresponds to class III water quality (moderately polluted). At the stations with highest anthropogenic pollution the saprobic index value corresponded to α-mesosaprobic area of self-purification, class IV water quality (polluted). Comparative analysis of structural characteristics of epiphyton communities at “polluted” and “relatively clean” stations has shown that taxonomic diversity may both increase and decrease with the raise of anthropogenic pollution level. The abundance and biomass of epiphyton at “polluted” stations were significantly higher due to development of filamentous green algae and cyanoprokaryotes. Among the dominant species observed were species-indicators of high pollution. Their presence leads to an increase in saprobic index values that indicate the occurrence of α-mesosaprobic conditions.