СООБЩЕСТВА БЕСПОЗВОНОЧНЫХ В СЕРОВОДОРОДНЫХ ИСТОЧНИКАХ КРАЙНЕГО СЕВЕРА (БАССЕЙН Р. УСА, РОССИЯ)

We assess the quality of surface water in water bodies located in the Middle Volga region (Russian Federation). The water quality is assessed using 19 chemical compounds and cilioplankton indicators, such as the total number of species, the abundance of each species, and, based on both of them, the saprobity index and the Shannon–Weaver diversity index (H). We classify the water quality from polluted to extremely dirty by using abiotic indicators, and from conditionally clean to dirty by means of biotic indicators. Using the logistic regression method, we are able to predict the water quality (clean or dirty) in correspondence with the species diversity index (H) and to clarify how the quality of the water is related to its physicochemical properties. The seven most significant chemical predictors of both natural origin (mineralization, hydro carbonates, and chlorides) and natural-anthropogenic origin (organic substances (according to BOD₅), nitrates, total petroleum hydrocarbons, iron), identified during the stepwise selection procedure, have a substantial influence on the outcome of the model. Qualitative and quantitative indicators of development of ciliates, as well as indices calculated on their basis, allow assessing with a very high level of accuracy the water quality and the condition of aquatic ecosystems in general. The Shannon index calculated for the number of ciliates can be successfully used for ranking water bodies as “clean/dirty”.

The method of ecological modifications was used to determine the invariant state of aquatic ecosystems in the Middle Volga basin. Based on the analysis of long-term regime hydrochemical and hydrobiological information using the methods of mathematical statistics (cluster, hierarchical cluster analysis, ordination methods), the studied water bodies were grouped according to the chemical composition of water, highlighting the main indicators of natural and anthropogenic genesis. We highlighted the general indicators of the chemical composition of water (temperature, salinity, hardness, content of oil products, chromium ions) that affect the change in the qualitative and quantitative characteristics of hydrobiocenoses, as well as specific indicators (nitrogen-containing compounds, phosphates, chlorides, sulfates, copper and iron ions), negatively affecting the quantitative and qualitative characteristics of hydrobiocenoses. A group of ciliates – cilioplankton (qualitative and quantitative characteristics) was used to assess the invariant state. Cilioplankton in the ecosystem of the Kuibyshev reservoir is characterized by high species diversity, which indicates anthropogenic stress. The quantitative characteristics of cilioplankton in rivers are low, and the community changes are ecological modulations. The share of rotifers development in zooplankton indicates the elements of ecological regress in water bodies, as well as anthropogenic eutrophication with elements of ecological regress (in most of the Kuibyshev reservoir). The level of zoobenthos development and its size, as well as the oligochaetes relative proportion indicate anthropogenic stress in the ecosystem of most parts of the Kuibyshev reservoir. The elements of ecological regress are traced only in the area of Chistopol. The water ecosystem in Tetyusha area is characterized as a transition from background to anthropogenic stress. The Vyatka and Mesha rivers are characterized as background rivers with the transition to anthropogenic stress. Anthropogenic eutrophication with elements of ecological regress can be traced in the Kazanka River. The Stepnoy Zai, Noksa and Ilet rivers has elements of ecological regress. Hydrobiocenoses indicators statistically depend on hydrochemical composition.

On the basis of the analysis of long-term data of chemical and biological monitoring, the ecological state of the Kuibyshev reservoir (the Republic of Tatarstan, Russia) was defined. There were used the dissolved oxygen, BOD, ammonium content and pollutants with excess of maximum allowable concentration (15 ingredients in total) as markers of chemical pollution. Total number of a zoobenthos and relative number of oligochaetes were chosen as biological indicators. Based on chemical and biological indicators it was noted that the lower sites of the Kuibyshev reservoir are less polluted in comparison with top sites which ecosystem now is in transition state from equilibrium to crisis.

Based on long-term data of chemical and biological monitoring, the risk of anthropogenic impact on urban water bodies was estimated (Kazan, Republic of Tatarstan, Russia). These chemical parameters were used as pollution markers: dissolved oxygen, BOD, ammonium compounds, as well as pollutants, which exceeded MAC (15 ingredients in total). The main biological indicators were the total number of phytoplankton, the relative number of oligochaetes in the composition of zoobenthos and the relative number of rotifers in the zooplankton. It is shown that urban aquatic ecosystems are in transition from equilibrium to critical state according to the degree of risk of anthropogenic impact.