Abstract
Qualitative and quantitative composition of potamozooplankton was studied in three outlets from mesotrophic lakes. The greatest taxonomic and quantitative similarity of zooplankton occurred between the outflows of the second and third lake, located in the lake-river system. The farther the lake was located in the lake-river system, the greater was the quantity of zooplankton in the outflow. Within a short distance between the outflow and the downstream section, there was a strong reduction of cladocerans’ communities, followed by copepods, while the communities of rotifers were reduced in relatively small quantities. The hydrological conditions and transparency had a strong impact on the rate of changes in the zooplankton community.