Features of Phytoplankton Distribution in Lake Sevan (Armenia) in Summer and Autumn 2019

The species composition, features of spatial distribution, and diurnal dynamics of phytoplankton in Lake Sevan in summer and autumn under the influence of abiotic and biotic factors have been studied. In the summer of 2019, low phytoplankton biomass was observed in Lake Sevan. Green algae dominated in biomass. The autumn biomass of plankton algae was significantly higher than the summer biomass, diatoms dominated, and the potentially toxic Cyanoprokaryota Nodularia spumigena was a subdominant. The highest biomass of phytoplankton was observed in the surface horizon, but at some stations deep maxima of biomass of some orders were noted. High zooplankton pressure was noted in the metalimnion, where the minimum total biomass of phytoplankton and the biomass of cyanoprokaryotes and green and diatom algae were recorded in summer.