Water Renewal Effects on Reservoir Zooplankton Communities

Water renewal may influence reservoir zooplankton communities through the mechanisms of dilution, transport (selective removal or addition), or through localized modifications of limnological conditions (e.g., light penetration, food quality, temperature) which then provide the setting for alteration of zooplankton community structure. An inverse relationship between reproduction in cladoceran zooplankton and water renewal time was found for six reservoirs sampled during summer 1980. This relationship suggests a strategic response in resource allocation by cladoaerans to dilution effects associated with water renewal. However, analysis of variation in cladoceran demography at different sites within each of the reservoirs and over a four-month period at a single site in one reservoir demonstrated that repoductive variation could be explained by spatial or temporal variation in limnological conditions and independently of transport or dilution processes associated with water renewal.