Assessment of the water quality of the Sukhona river tributaries (Vologda oblast) according to zoobenthos indicators

Hydrobiological studies of 40 tributaries of the Sukhona River (White Sea basin) were conducted in the summer of 2016–2018. The assessment of the ecological state of the rivers was carried out on the basis of quantitative and qualitative data from zoobenthos. According to zoobenthos indicators, the cleanest rivers include rivers with high flow rates; the most polluted are rivers flowing near populated areas, as well as through wetlands. The contribution of the hydrological characteristics of the catchment area to the formation of water quality is shown. The indices obtained in some cases show contradictory results. The values of the EPT, ASPT, BMWP, and OQR indices may decrease in small watercourses. The value of the Goodnight-Whitley index can be influenced by swamps located in the catchment area. It is shown that the background values of the saprobic index for the watercourses of the taiga zone are in the range of 1.5–2.5. The indices of species diversity and saprobity should be considered in a comparative way.