Zooplankton changes in the longitudinal profile of the non-regulated site of the Ochyor river (Kama basin) below of the Ochyorskoe reservoir

The distribution of zooplankton of the Ochyor River on the section between the Ochyorskoe and Pavlovskoe reservoirs and its closed-form oxbow in the summer and autumn of 2015 is considered. Observed 73 species of zooplankton (42 species of rotifers, 22 species of cladocera, 8 species of copepods and 1 species of mollusks). As the river profile moved down along the longitudinal profile of the river, the species diversity of the communities increased or remained at a constant level, general indicators of quantitative development of communities and abundance indicators of individual groups of animals decreased, and the composition of dominant complexes varied. During the summer period, the total biomass of cenoses decreased from 0.27 to 0.03 g/m3, the strength reduced from 46.1 to 7.6 thousand ind./m3, in autumn the biomass decreased from 1.87 to 0.05 g/m3, the strength - from 192.7 to 18.3 thousand indVm3. Zooplankton of the oxbow in terms of quantitative development significantly exceeded the river communities in the summer, not differing from the poorest cenoses of the river in the autumn.