Vol 11, No 1 (2018)

Hydrochemical and hydrobiological characteristics have been studied at 13 sites in the Okhta River within the precincts of St. Petersburg in 2010. The Water Pollution Index (WPI), calculated according to hydrochemical parameters, characterizes the river water quality as “very polluted” to “extremely polluted.” According to the Pantle–Buck–Sládeček Saprobity Index, obtained on the basis of macrozoobenthos characteristics, polysaprobic and α-mesosaprobic zones can be distinguished in the watercourse. The species richness of river macrophytes is low (18 species). The Macrophyte Water Quality Index makes it possible to assess water quality in the range from “polluted” to “very polluted” water. Macrophyte trophic indexes MTR, IBMR and TIM indicate a high trophy level in the watercourse sites. Based on the analysis of hydrochemical materials and the data on macrozoobenthos and macrophytes, the general tendency is similar: deterioration of water quality downstream. Macrophyte characteristics reflect changes in hydrochemical parameters downstream the river course. А strong correlation (r =–0.76) is found between the Macrophyte Water Quality Index and WPI. The possibility of using the data on macrophytes in small rivers for assessing water quality is demonstrated.

The prevalence of processes of the increase in abundance and changes in the sexual structure of Prussian carp populations in waterbodies differing dramatically in ecological properties and distant from each other (Lake Sevan and Rybinsk Reservoir) indicates the presence of global factors affecting climatic zones. The increase in environmental temperature due to global warming may be such a factor. Experimentally proven high thermophilicity and the thermal stability of Prussian carp, as well as its low sensitivity to hypoxia, provide some advantages for this species over many other fish inhabiting the same waterbodies.

Threshold concentrations of sodium, potassium, calcium, and magnesium in water determining the borders of the Chironomus balatonicus range in waterbodies are 0.6–0.62, 0.11–0.12, 0.071–0.073, and 0.022–0.028 mmol/L, respectively. In the freshwater section of the Curonian Lagoon of the Baltic Sea and other waterbodies with weakly mineralized water where the content of ions is lower than the threshold values, larval Ch. balatonicus cannot dwell because of the impossibility of maintaining the ionic balance between the organism and environment. The threshold concentrations and rates of loss of ions from an organism in various species of aquatic organisms are comparatively analyzed.

Dynamics of the morphometric and physical properties of hemocytes of the Prussian carp Carassius gibelio (Bloch) under the influence of a temperature factor has been studied with atomic force microscopy in experiments in vitro. It is found that, at a low incubation temperature (5°C), as opposed to room temperature (20°C), morphometric parameters change in erythrocytes; at a high temperature (40°C) they change in polymorphonuclear leucocytes. The low incubation temperature reduces the adhesion and elasticity of polymorphonuclear leucocytes and erythrocytes of C. gibelio, whereas a high incubation temperature leads to a decrease in adhesion in polymorphonuclear white blood cells.

Chara dominii Vilh. is a new species in the flora in Russia. It has been found in Altai krai, Astrakhan oblast, and the Republic of Kalmykia. These findings change the concept of the northern border of the species living range considerably, as practically all C. dominii finds reported up to now were made in Central Asia. A description of the samples under study is given, and the living range of the species is characterized.

The features of the floristic composition and dynamics of the biomass of phytoplankton in shallow and deep areas of the Volga reach in the Rybinsk Reservoir have been studied during years with different thermal and water-level regimes (2009–2011). The floristic diversity and biomass of phytoplankton increase with a decrease in depth. The increase in water temperature at low water level stimulates phytoplankton vegetation in the pelagial zone and a decrease in biomass in the littoral zone, while a high diversity of algocenoses is recorded irrespective of habitat. The contribution of filamentous algae and cyanoprokaryotes to the biomass increases in the shallow littoral part; in the open part of the reservoir, the biomass of mixotrophic flagellates decreases. Their abundance, as well as the abundance of zignematales, increases with decreasing depth.

Seasonal and interannual dynamics of phytoplankton content (chlorophyll a), organic matter, and nutrients, as well as water temperature and water transparency, have been analyzed for the weekly observations performed in the Ob River from February to November, 2012–2015. The period of intensive phytoplankton growth (>10 mg/m³ Chl. a) lasts 70–90 days at a long spring flood in average and high-water years; in the absence of flooding during a dry year it exceeds 110 days. Seasonal phytoplankton dynamics is characterized by two summer maxima in July–August and in September (Chl. a content ~25 mg/m³); during a dry year, there is also a peak in June (up to 37.3 mg/m³). Seasonal dynamics of Chl. a in summer–autumn low water is closely related to the water temperature; in high water and autumn low water it is closely related to water transparency; in summer it is closely related to BOD5; and, in the summer–autumn period, it is closely related with nitrate content. According to the annual average (5.7–11.1 mg/m³) and maximum (19.2–35.0 mg/m³) concentrations of chlorophyll a, the trophic status of the river corresponds to mesotrophic–eutrophic water and the water quality corresponds to the second class, i.e., “clean water.”

The American rotifer Kellicottia bostoniensis (Rousselet, 1908) was first recorded in the Kama Reservoir (Kama River, Middle Volga basin) in 2012. The species was found in over 70% of the samples; its maximum abundance was 2000 ind./m³. This alien species co-existed with closely related native species K. longispina (Kellicott). This is the easternmost location (56°–57° E) for K. bostoniensis in the Volga River basin and in Europe.

Interannual variations in species richness and quantitative parameters of macrozoobenthos in floodplain lakes of the Khoper Nature Reserve have been studied to reveal their dependence on flood regime and overgrowth by macrophytes. It has been shown that a particular species richness of macrozoobenthos is preserved for several years. Interannual variations in characteristics of lakes, particularly in the flood period, determine the changes in quantitative parameters of macrozoobenthos. The overgrowth rate of lakes by macrophytes does not exert an effect on species richness and quantitative parameters of macrozoobenthos, but determines its saprobiological structure. The flood period necessary for the formation of the most abundant communities of macrozoobenthos in the studied lakes is 30 days. Nevertheless, this is not the main factor determining its quantity in lakes constantly connected with the river by a channel. It is confirmed that drying or a sharp drop in water content of the river play the role of a trapping point and triggers ecosystem transformations in small water bodies.

The specific/volumetric activity of radionuclides has been determined at global background levels in surface waters, bottom sediments, and hydrobionts at the site of the planned hydrotechnical facilities of the Baltic nuclear power plant (NPP). The presence of Sr⁹⁰ and Cs^l37 in the water medium due to global processes of the formation of radioactivity in the natural environment and the content of ³H have been studied. It is established that the background values of the specific/volumetric activity of radionuclides are significantly lower than the admissible values according to NRB-99/2009, being at the level of the previous years (2009–2014). The results of these studies will serve as a basis for precision instrumental estimates of the effect of the Baltic NPP operation on the environment and will also be used to establish the background values of environmental parameters in the nuclear power site.

Relationships between beetles of the family Heteroceridae and other organisms are reviewed using information that has been compiled from primary and secondary sources. A brief description of each species involved in the interspecies relationships under analysis is given.