Zooplankton of the Vychegda River under Conditions of Treated Wastewater from the Pulp and Paper Industry

Like most northern rivers, the Vychegda River, the second largest water system in the Komi Republic and the main tributary of the Northern Dvina River, has experienced an intense anthropogenic load. Agricultural, domestic, and, to a greater extent, industrial wastewaters are currently the main polluting sources of river waters. Among the numerous enterprises operating here is Mondi Syktyvkar JSC, the largest pulp and paper enterprise in Russia, which is located on the Vychegda River banks. The composition and structure of the zooplankton communities were studied in the Vychegda River area, where the effect of wastewaters from the pulp and paper plant is observed. The aim of the research is to determine whether there is a negative impact of the conditionally treated wastewaters on the aquatic biota. As a result, a rich species composition and the quantitative development of zooplankton communities were established for the studied river area. Rotifera was the dominant group on the species richness, abundance, and biomass. This is a characteristic feature of zooplankton communities in the watercourse as a whole. The indicator species of waters with a high level of pollution were registered both at points located in the area of wastewater influence and on the background river plots. Species that are not typical to the natural waters of the river were found at points of wastewater discharge. The dominant complexes are represented by 9–15 or more species. Their composition differs in background, wastewater and downstream points. According to the state of zooplankton communities, the river waters in the studied area are conditionally clean, except for points located downstream of the wastewater discharge, where they are qualified as eutrophic.