Health risk assessment related to water quality and microcystin contamination of water in the Kuibyshev Reservoir was conducted in August 2012 during the period of algal bloom. The health risk during recreational activity was estimated for potential exposure to extracellular microcystins. Microcystin content in water measured by the indirect competitive ELISA method was in the range from 0.21 to 26.96 μg L⁻¹. The results of the present study show that the health risk can reach a dangerous level even at 1 h of exposure due to the high concentration of extracellular microcystins in the water.

The study of microplastic content in water, sediments, gills and gastrointestinal tract of bream (Abramis brama) at the mouth of the Mesha River, the right tributary of the Kama River, was conducted. The content of microplastics in water was found at the level of 20.5 ± 22.3 units/m3, in bottom sediments 44.7 ± 41.8 units/kg, in fish gills 12.3 ± 8.4 units/example, in the gastrointestinal tract 14.5 ± 11.5 units/example. Fibers dominated in water samples, in the gills and gastrointestinal tract of fish, fragments dominated in the sediment. Correlation analysis showed the presence of a negative relationship between the content of microplastics in the gills, gastrointestinal tract and biologic indicators of studied fish. In terms of the frequency of occurrence and content of microplastics in the gills and gastrointestinal tract, the contamination of the studied fish is at a high level compared to literature data, which is associated with the feeding behavior of bream.

The negative consequences of global climate change are widely known, in particular leading to a decrease in soil fertility and a decrease in the efficiency of crop production. In connection with the above, approaches to greening agriculture are constantly being developed, which should lead to improved soil quality, preservation and increase in the amount of nutrients in it, as well as a reduction in greenhouse gas emissions. One of these approaches may be the use of peas as ground cover plants to reduce CO2 emissions from bulk soil, due to the fixation of C in phytomass, which will later be plowed into the soil. To evaluate the effectiveness of this approach, a vegetation experiment was conducted in a greenhouse under different temperature conditions (20°C, 25°C, 30°C) with soil on which pea plants (Pisumsativum) were grown and soil without plants (imitation of open arable land) . In the dynamics of the experiment, indicators characterizing the process of carbon accumulation in phytomass were assessed, namely the rate of increase in plant phytomass and chlorophyll content in leaves, as well as the process characterizing CO2 emission from the soil - an increase in the intensity of soil basal respiratory activity under peas over that of bulk soil. Next, the carbon balance was calculated for each temperature regime. It was shown that with an increase in temperature from 20°C to 30°C, there is a decrease in C fixation in plant phytomass and a decrease in CO2 emission due to the respiratory activity of the soil microbial community. The maximum fixation of C when growing peas (Pisumsativum) was established for a temperature regime of 20°C and amounted to 585 kg C/ha.

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.