State of the Benthic Communities of the Vychegda River under the Influence of Treated Wastewater from the Pulp and Paper Industry

Abstract—The composition and diversity of benthic communities, as well as the current ecological state of Vychegda River in the zone of influence of wastewater from pulp and paper production, are characterized. A high diversity of benthic fauna and quantitative indicators of its development that atypical for benthic biocenoses in the middle reaches of Vychegda River were registered. In the zoobenthos composition, 23 taxonomic groups of benthic invertebrates were identified. For the seven model groups, 125 species and forms were identified, as well as a persistent complex of species that predominate in the studied section of the river. Indicator species of o-ß- and ß-saprobic conditions were dominant in the model groups. In general, indices for water-quality assessment based on the composition and structure of benthic invertebrate communities characterize the state of the river at the monitoring site as satisfactory. An exception was the wastewater-discharge points, where the role of indicator species of ɑ- and polysaprobic conditions was higher and the values of most of the indices were significantly lower.