The dynamics of cladoceran assemblages in response to eutrophication and planktivorous fish introduction in Lake Chenghai, a plateau saline lake

Lake Chenghai, a brackish lake located in southwest China, has changed from oligotrophic to mesotrophic and finally eutrophic conditions since the 1990s. In the late 1990s, planktivorous icefish were introduced into the lake, which dramatically altered the fish population. A paleolimnological evaluation using the cladoceran remains was conducted in order to analyze the effects of increasing nutrient load and fish introduction on the cladoceran community of this lake. Our results showed that the dominant cladocerans were littoral species, with a low abundance of planktonic Bosmina in the sediment. Increasing eutrophication since the late 1990s greatly enhanced the abundance of cladoceran assemblages, especially for the species that prefer eutrophic conditions. Meanwhile, the species which prefer oligotrophic conditions were extirpated. The changes in Daphnia ephippium length suggested that the planktivorous icefish have varying effects on the body size of different species.