on the criteria for the assessment of the state of polluted freshwaterecosystems with an example of the small river on the eastern edge ofeurope (perm krai, russia)

The use of abiotic ecological indicators in environmental monitoring does not always reliably reflect the level of anthropogenic impact on aquatic ecosystem. our study aims to estimate possible differences in abiotic and biotic index-based assessments of the impact of industrial pollution on water quality in the small boreal river located at the eastern edge of europe (perm krai, russia). we analyzed the contamination of an 13-km long river by major organic and inorganic ions, trace elements, and thermal pollution. to evaluate the toxicity of bottom sediments, threshold effect concentration (tec), probable effect concentration (pec), and potential effect concentration quotient (mpecq) were calculated from the concentration of heavy metals. also, benthic macroinvertebrates were sampled from headwaters to the mouth of the river. we found the presence of the members of the ept taxa at the sites with a high concentration of heavy metals, which can be explained by the tolerance of local invertebrates to specific pollutants. apart from that, our results show that in the middle reach of the river, toxic effect of a nitrite-ion high concentration contradicts the presence of gill breathing crustaceans sensitive to this type of pollution. this can be explained by the high concentration of chlorides at this site, which leads to reduction of nitrite toxicity. further work should be focused on developing abiotic indices that account for the sensitivity of local invertebrates to specific pollutants, while comprehensive pollution assessment should include antagonistic or synergistic interactions of various pollutants.