Macrozoobenthos in mid-mountain lakes of river Multa basin (Republic of Altai)

Abstract

In August 2020, taxonomic composition and quantitative characteristics of zoobenthos from 4 lakes located in the upper reaches of the R. Multa basin (the R. Ob basin) were studied. Because of the basin inaccessibility the hydrobiological information about these lakes was previously fragmentary or absent at all. The data on macrozoobenthos composition and its structure were not available. In these lakes, 49 species of benthic invertebrates from 7 classes were identified, i.e. Demospongiae (1), Turbellaria (1), Oligochaeta (3), Gastropoda (4), Euchelicerata (1), Crustacea (1) and Insecta (38). Among insects, Diptera were the most diverse (22 chironomids out of 23 species). Beetles, mayflies and caddisflies were also found. In terms of species number, abundance and biomassб chironomids were the dominant taxonomic group in the studied lakes. The species composition of macrozoobenthos consisted of species widely spread in the Palearctic and Holarctic. The investigated lakes differed in species composition of zoobenthos. When comparing the species lists of benthic animals, lakes Sredneye Multinskoye and Poperechnoye were similar at most, whereas the fauna of Lake Nizhneye Multinskoye was the most original. The studied water bodies were distinguished by poor macroinvertebrate development and thereby corresponded to ultra-oligotrophic and oligotrophic reservoir types. The oligochaete index by Goodnight and Whitley corresponded to quality class I–II, i.e. “conditionally clean” and “slightly polluted waters”. We defined the trophic structure of macrozoobenthos of lakes and identified five main trophic groups of hydrobionts (Deposit feeders, Сollectors-detritus feeders and facultative filter feeders, Collectors-obligate filter feeders, Shredders, Predators), among which Collectors-detritus feeders and facultative filter feeders dominated.