Day-night differences in crustacean zooplankton in Lake Glubokoe and Mozhaysk Reservoir (European Russia)

We present the first results of our research on day-night differences of crustacean zooplankton in Lake Glubokoe and Mozhaysk Reservoir. We found increases in pelagic crustacean zooplankton density and biomass at night in both lakes. Changes in quantity and species composition were more prominent and statistically significant in Mozhaysk Reservoir than in Lake Glubokoe. We observed only a slight increase in zooplankton density and biomass and a shift between dominant species distribution in Lake Glubokoe. The changes we observed appear to be caused by horizontal zooplankton migration.