Pelagic cladocera in upper volga water reservoirs

The results of cladoceran crustaceans studies in the pelagial of the Ivankovo and Uglich water reservoirs were generalized. In the period of 1973-1995, both waterbodies were similar in terms of Cladocera species composition and the dominating complex. The list of species composition of pelagic cladocerans has increased since the 1950s. The highest abundance of cladocerans was observed in the Ivankovo water reservoir. Daphnia cucullata G. Sars has been stably dominant in zooplankton summary biomass, while Chydorus sphaericus (O.F. Muller) and Bosmina longirostris (O.F. Muller) prevailed in terms of abundance. Changes in the pelagic cladoceran complex composition is evidence of the waterbodies' eutrophication. The share of Cladocera in the zooplankton's total summer biomass was 68 and 53% in the Ivankovski and Shoshinski stretches of the Ivankovo water reservoir, correspondingly, and 60% in the Uglich water reservoir (on average for 1970s-1990s).