Long-term changes in the community of planktonic crustaceans in Lake Glubokoe in relation to predation and competition

Studies on the planktonic Crustacea in Lake Glubokoe (Moscow region) from 1897 to 1982 have been reviewed. After 1965, when most of the swamp water inflow was diverted from the lake, certain populations have penetrated into deeper layers, while the average overlap in the community has dropped. The summer dominant Mesocyclops leuckarti disappeared and Chydorus sphaericus appeared in mass quantities; this development was not associated with biomass changes of blue-greens. The Cladocera/Calanoida ratio and the relative abundance of certain species showed no considerable changes. The effect of Chaoborus, Cyclops and Leptodora in the 70's on the crustacean populations was insignificant in spite of the increasing abundance of these genera after 1965. Analysis of the dynamics of the clutch size and the density of lake populations in the 1970's and 1980's revealed food limitation and competition in herbivorous Cladocera. In laboratory experiments with lake water they always competed, though the intensity of their interaction varied depending on the species combinations.