Environmental variables regulating the phytoplankton structure in high mountain lakes

The research on the Kolsay mountain lakes was carried out in August 2015. Phytoplankton was represented by 28 species. The richness of algal communities increased with a decrease in altitude of the lake. Nutrients were one of the main factors influencing the diversity, quantitative indicators and size structure of phytoplankton of the Kolsay lakes. The nitric nitrogen as well as manganese and silicon played the main role with the exhaustion of phosphorus. The average algal cell mass is decreased in the gradient of saprobic index values. The cell average mass was also influenced by the ammonium and total toxic pollution, the latter reflected in the WESI index. The results of multifactorial analysis allowed us to assume that organic contamination enters Kolsay lakes together with a number of toxic elements, with chromium in particular, stimulating the growth of algal species abundance in general. The CCA analysis revealed groups of species that are sensitive to the content of silica (diatoms), salinity (mostly green algae), manganese, chromium, nitrite and nitrate nitrogen (most species). The WESI index showed a slight inhibition of phytoplankton in the three out of four Kolsay lakes despite low concentrations of heavy metals. Cadmium, copper and iron made the main contribution to the overall level of toxic pollution of studied lakes.