Сукцессии зоопланктона малых мелководных озер после проведения мероприятий по экореабилитации

Abstract

The need for eco-rehabilitation of water bodies affected by strong anthropogenic influence increases greatly with an increase in the area of urbanized territories. The effectiveness of such measures may be evaluated by studying successions of hydrobiont communities in a rehabilitated water body. In 2017, actions were taken to rehabilitate the Lebyazhye Lakes system (Kazan), which included deepening the basins of Bolshoe Lebyazhye Lake and Svetloe Lebyazhye Lake to 4 m, isolating the bed of future basins with bentonite mats, supplying water from Izumrudnoye Lake through a pressure conduit, filling the lakes with water, and improvement of the shores. Then, in 2018–2021, zooplankton indicators of these lakes were studied and models of its food webs were proposed. After the work was completed, the lakes were successfully colonized by zooplankton: in 2018, the identified assemblage included 106 species, with 51 species of rotifers (46%), 36 species of cladocerans (34%) and 19 species of copepods (18%). However, in the absence of higher aquatic plants, a strong “bloom” of water was observed with the predominance of blue-green algae in the composition of phytoplankton and low water transparency. In 2020–2021, the zooplankton composition showed a decrease in the total number of species and the number of species in the sample, a decrease in the production in communities, a change in the composition of dominant species towards representatives of the genus Brachionus, and an increase in the variability of biomass dynamics. All these suggested instability and the gradual simplification of the community. In 2021, obligate predators disappeared from one of the lakes, which led to the shortening of food chains.