Quantitative development of zooplankton in waterbodies and watercourses of the Great Lakes Depression (Mongolia)

The indices of the zooplankton of various waterbodies and watercourses of the Great Lakes Depression (Mongolia) are analyzed. The maximum quantity of zooplankton is registered in freshwater bodies. Irrespective of the waterbody type, the greatest number and biomass of zooplankton are recorded in the littoral zone, where communities are characterized by a high abundance of rotifers, including the indicator species of eutrophic waters. This indicates a high degree of organic load from the catchment area. In comparison with the data obtained by the end of 1970s, the zooplankton biomass decreased with a concomitant increases in the shares of rotifers and cladocerans. These changes are most pronounced in the freshwater ecosystem. The quantitative development of the zooplankton of watercourses depends on the character of the river head, the location of sampling stations along the watercourse’s channel, and the water current velocity.