Zoobenthos of the lower part of the Vychegda river and its tributaries

The study results of zoobenthos of the lower part of the Vychegda River and its tributaries are presented. Bentofauna includes 21 taxons of invertebrates ranging from 4 to 14 between the water-bodies. The number of invertebrates in the rivers varies from 300 to 17 850 inds./m2 being 5310±1403 inds./m2 on the average. Invertebrate biomass ranges from 0.1 g/m2 in sandy grounds to 28.8 g/m2 in sandy-silty grounds averaging 5.8±2.6 g/m2. By the index of E.V. Balushkina, the Vychegda River along 222 km from the mouth is a polluted river. For the other water-bodies, the E.V. Balushkina index ranges from 2.9 to 6.5 which allows them to be classified as moderately polluted water-bodies.