Zamana S.P., Zubkova V.M., Makakhanyuk Zh.S. Geoecological Assessment of Aquatic Ecosystem Components of the Khodtsa River in the Moscow Region under Anthropogenic Load // Ecosystems: ecology and dynamics. No 4. 2025. P. 63-104. | Abstract | PDF | Reference

Presently, small rivers are under a extreme anthropogenic load, especially in regions with many industrial enterprises and high population density. Therefore, their abiotic and biotic components undergo negative changes, which makes a geo-ecological assessment of the aquatic ecosystem of one of them, such as the Khodtsa River in the Moscow Region (its source is at Elektrostal, and its mouth is at Pavlovsky Posad), quite relevant. We addressed the following objectives: determining pollutants in water, snow, coastal soil, bottom sediments, higher aquatic vegetation, and fish, as well as assessing bioindicators, the bioproductivity of higher aquatic vegetation, and environmental risk zones in different sections of the river.

We based our research on the data from field studies conducted in 2017-2023 at various sections of the Khodtsa River, and from laboratory studies. The general methodology included sampling water, snow, coastal soil, bottom sediments, and plants at 3 locations: source of the river, intermediate point, and mouth of the river. Standard methods from the Register of Quantitative Chemical Analysis were used for sample analysis. Currently, quantitative assessment of the risk of ecosystem deterioration is primarily based on the level of pollutant concentration exceeding the established standard in a specific component. However, when addressing environmental issues related to chemical pollution, it is important to consider the response of living organisms to pollution using bioindication and biotesting. Since abiotic components such as water, bottom sediments, and coastal soil in an aquatic ecosystem determine the most important processes that influence the functioning of biotic components (i.e., all living organisms), we used an ecosystem approach based on a comprehensive quantitative study of the migration of priority toxic elements in all links of the biogeochemical food chain of the Khodtsa River aquatic ecosystem.

Our studies of the river’s aquatic ecosystem revealed patterns of heavy metal migration in the “water – bottom sediment – coastal soil – plants – fish” system. Iron, cadmium, lead, ammonium nitrogen, and petroleum products were the predominant pollutants at various sampling sites along the river. Compared to the coastal soil, the bottom sediments were significantly more contaminated with heavy metals at the source and intermediate points. Spatial variability of heavy metal content in sedge (Carex aquatilis) was revealed, depending on their content in water and bottom sediments. Moreover, an acropetal pattern of heavy metal distribution in plants was observed: roots accumulated 7-24 times more Cd, 2-4 times more Pb, and 112-251 times more Fe than shoots. Therefore, to determine the pollution of the aquatic ecosystem with heavy metals, we recommend using sedge (especially its roots) as a bioindicator, which can also be used for phytoremediation of small rivers. The biological productivity of higher aquatic vegetation increased from the source to the mouth of the Khodtsa River.

A complex pattern of heavy metal accumulation in the muscle tissue of the studied fish species such as Amur sleeper and common roach was revealed. During a comprehensive assessment of the pollution of abiotic and biotic components, zonation of the river was carried out. The Khodtsa River is characterized by predominant chemical pollutants (heavy metals, petroleum products, ammonia nitrogen). Zones of increased environmental risk were identified at the source and intermediate point, indicating a significant contribution to pollution from municipal and industrial discharges from Elektrostal. However, later in 2023 monitoring of the coastal soil using the lettuce as a test object revealed that the heavy metal content at the intermediate point was higher than at the river’s source, which is explained by a significantly reduced pollutant input from Elektrostal enterprises. Therefore, for the most rapid and cost-effective assessment of river pollution by heavy metals, phytotoxicity testing of coastal soil using the lettuce as a test object should be used for monitoring.

Keywords: ecosystem approach, water, bottom sediments, coastal soil, water sedge, fish, heavy metals, bioindicators, phytotoxicity, river zonation.

DOI: 10.24412/2542-2006-2025-4-63-104

EDN: CYWCLE