Summary
The effects of water level fluctuation on the zooplankton community of Lago Grande (Rio Solimões, State of Amazonas, Brazil) were investigated from April, 1979 to March, 1980. Quantitative samples of zooplankton, water depth and Secchi disc transparence were taken at two stations located in the middle of the lake. Highest zooplankton densities were observed during the low water period, and these were correlated with higher nutrient levels. These nutrients appears to come from the surrounding inundation forest and from the substrate of the lake. The effects of high turbidity on the zooplankton community is also discussed, especially in relation to Cladocera.