Interannual Changes in the Quantitative Parameters and Structure of Invertebrates in the Littoral and Pelagic Zones of Lake Sevan (Armenia) with Fluctuations in Meteorological Conditions and Fish Biomass. I. Summer Zooplankton

Annual changes in the quantitative characteristics and structure of zooplankton in the pelagic and littoral zones of Lake Sevan in October have been determined by a number of factors, among which the biomass of the main planktophage, whitefish (Coregonus lavaretus L., 1758), have the greatest effect. The richest communities form due to Cladocera upon a decreased biomass of whitefish, minimum increase in the water level, and high average monthly temperatures for the period of April–October. In the littoral zone, the zooplankton is affected by a number of unaccounted factors, and the influence of planktophagous fish, mainly inhabiting deepwater areas, is less pronounced. A significant increase in biomass of planktophagous fish in 2016–2017 leads to a reduction in the quantitative characteristics of zooplankton, resulting in decreased water clarity.