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