STRUCTURE AND DYNAMICS OF PHYTOPLANKTON OF LARGE SHALLOW-WATER OVERGROUND LAKES (VOZHE AND LACHA, VOLOGDA AND ARKHANGELSK REGIONS, RUSSIA)

Abstract

A comparative analysis of the diversity, abundance, biomass, composition of dominant species, size characteristics of phytoplankton and saprobity of the waters of shallow large overgrown lakes Vozhe, Lacha, as well as the rivers Svid and Onega in June 2015 is presented. The data obtained are compared with the results of previous studies in the 1970s years. It was found that in the 2000s, there was a significant increase in the number of phytoplankton in lakes and a change in the composition of dominant species. Non-heterocyst cyanoprokaryotes (Aphanocapsa holsatica, Planktolyngbya limnetica) began to dominate in phytoplankton, which is associated with increase of ammonium concentration. The average biomass of phytoplankton in lakes (2.6 g/m3) has remained practically unchanged since the 1970s and was typical for mesotrophic type waters. In the Lacha Lake characterized by lower transparency, high degree of overgrowth, salinity and saprobity of waters, phytoplankton was distinguished by lower floristic diversity, higher abundance, dominance level, and the smallest cell sizes.