Biotic Indices and Metrics of Zoobenthos in the Assessment of the Ecological State of a Large Mixed-Type River

The current state of zoobenthos communities has been studied in a large Siberian river, namely, the Chulym River. Bioindication indices have been calculated to determine the water quality. The use of the integral indicator has made it possible to assess the water quality in a single system in compliance with the Russian standards. The high water quality (“conventionally clean”) has been recorded in the middle reaches, where the river is semi-mountainous, as well as in the zone of its transformation from the semi-mountain type to the lowland type. Deterioration of the water quality (“dirty” water) has been recorded in the lowland reaches. It is shown that the assessment of the ecological state of water bodies using bioindication methods should take into account natural environmental factors, in particular, the type of bottom sediments.