Hydrobiocenoses of lake Tulos, Southwestern Karelia

The following paper assesses the current state of the phyto- and zooplankton and benthic communities of Lake Tulos, which geographically is a part of the Green Belt of Fennoscandia. The lake is located on the territory of the planned National Park «Tulos». The species diversity, the ratio of major taxonomic groups and the structure, abundance and biomass of predominant aquatic organism species in the littoral and pelagic zones of the lake were studied. According to the obtained results (the level of quantitative development and the ratio of phytoplankton species during the growing season 2018) the waters of Lake Tulos can be assigned to the third quality class, grade 3a («fairly clean»), which corresponds to the β-mesosaprobic zone by the saprobity scale. According to Pantle-Bukk saprobity index calculated on the basis of zooplankton, the lake’s water can be attributed to oligosaprobic – the 2^nd class of quality, pure natural waters. Indices of abundance of macrozoobenthos correspond to the oligotrophic class, according to the ratio of its main groups, the lake belongs to the «chironomid» type of lakes. The reservoir has a high recreational potential, according to the ichthyofauna composition it belongs to the water bodies of the first fishery category. Lake Tulos is a reference water body convenient for environmental monitoring in near-border areas.