Quantitative characteristics of zooplankton and zoobenthos communities and water quality in the Nercha River in the conditions of Transbaikal Region

Abstract

Studies on species diversity of zooplankton and zoobenthos communities were carried out at the Nercha River at the middle and lower parts of its waterway. The Nercha River located in Transbaikal region, belongs to the upper Amur basin. The Nercha River is second order tributary of the Amur river. In plankton community we had found 42 species of invertebrates belonging to 27 genera, 15 families, 7 orders and 4 classes. In plankton rotifers were characterized by the highest species diversity and presented by 24 species and subspecies. Cladoceras were presented by 16 species and copepods – by 2 species. In benthic community we had found 133 taxa of different systematic level belonging to 6 classes: Nematoda, Arachnidae, Clitellata, Insecta, Gastropoda, Bivalvia. The total number of taxa were distributed among 35 families, 52 genera, 65 species. Amphibiotic insects were dominating group in benthos. Abundance of zooplankton ranged from 0.02 to 1.53 thousands ind/m2. Benthic organisms abundance ranged from 0.12 to 6.30 thousands ind/m3. Zooplankton biomass varied from 0.01 to 40 mg/m3. Biomass of zoobenthos varied from 0.003 to 28.46 g/m2. Number of species of zooplankton in samples varied from 2 to 22. Number of benthic species in sampes varied from 4 to 39. The index of zooplankton species diversity varied from 0.5 to 4.2 bit/ind, zoobenthos – from 1.04 to 4.47 bit/ind. Majority of recorded pelagic and benthic species belong to widespread holarctic and palearctic types of distributio n. The water quality was characterized mainly by II and III classes: pure – the moderate polluted waters respectively.