Zooplankton distribution along small river profile under high anthropogenic load (on the example of Tsivil river, Middle Volga region)

The zooplankton composition, structure and abundance modifications in beaver inhabited steppe small rivers during the main hydrological phases were analyzed. Revealed seasonal changes differ from such in small rivers in the South taiga region. In the beaver built ponds during the main hydrological phases Cladocera primary filtrators influence is more essential, Copepods are not abundant during spring and autumn floods, being fed on the substrate surface organisms are not numerous during autumn flood.