Assessment of the ecological status of some small rivers of the State Nature Reserve «Kologrivsky Forest» by zoobenthos communities

The article presents the results of studying the ecological state of some watercourses of the State Nature Reserve "Kologrivsky Forest" named after M. G. Sinitsyn according to the indicators of macrozoobenthos communities. The species diversity of macrozoobenthos, the most numerically represented taxonomic groups and species of zoobenthos organisms are presented. The abundance and biomass of this group of aquatic organisms, the features of the trophic structure, the values of the Shannon species diversity index and the Pyele equalization index for the small Sekha, Ponga, Lomenga, Londushka and Chernaya rivers were determined. The assessment of the water condition in accordance with the saprobiological system of Pantle - Buck and Woodiwiss, as well as the assessment of water quality using the biotic indices BMWP and ASPT is given. The faunal list of discovered representatives of macrozoobenthos is represented by 70 lower defined taxa (LDT). Insect larvae are the most numerous in all the rivers studied. The highest abundance rates of this group are noted in rivers with sandy bottoms, in conditions of greater overgrowth of the banks by macrophytes, whereas in conditions of sandy-muddy and muddy soil, the number of insects decreases. The greatest taxonomic diversity is characteristic of such trophic groups as predators and gatherers-detritophages. It was revealed that the Ponga, Sekha, Londushka and Chernaya rivers, characterized by a fairly rich species composition of zoobenthos, belong to the β-mesosaprobic according to the Pantle - Buck saprobiological system. According to the Woodywiss index, the Ponga, Sekha and Chernaya rivers are characterized as "moderately polluted" watercourses, while the Lomenga and Londushka rivers - as "polluted". The value of the BMWP index indicates the high water quality in the rivers of the reserve and is rated as "exceptional" in the Pong River, "very good" in the Sekha and Chernaya rivers, and "good" in the Lomenga and Londushka rivers. The ASPT index varies in different rivers from 4.7 ("very good" water quality) to 6 ("excellent").