The aquatic surface microlayer is located at the atmosphere–hydrosphere boundary and occupies 70% of Earth's surface, covering all water bodies. The depth of the surface microlayer is about 50 μm. A special microbial community called neuston is formed there. The total bacterial abundance in the surface microlayer (SML) and underlying waters (UW) of LakeBaikalwas studied using epifluorescence microscopy. Physicochemical features of the surface microlayer of LakeBaikalwere revealed for the first time. The SML was sampled throughout LakeBaikalin May–June of 2013 to 2016 and in August of 2013, 2015 and 2016. SML samples were taken from a boat, mainly during calm weather, using Garrett’s metal mesh screen (a diameter of 26.5 cm). The average values of total bacterial abundance in the SML varied through years within a range of (0.93–1.49)×10⁶ cells/mL in May–June and (1.73–2.24)×10⁶ cells/mL in August; in the UW, at a depth about 15–20 cm, there were (0.79 – 0.89)×10⁶ cells/mL in May– June and (1.15–1.4)×10⁶ cells/mL in August. Significant differences and a direct relationship between the total bacterial abundance in the surface microlayer and underlying waters ofLakeBaikal in the summer period have been shown. Differences between the chemical composition of the surface microlayer and the subsurface water layer in all studied seasons were revealed. The surface microlayer was enriched with PO43-, total organic carbon and suspended particulate matter as compared with the underlying waters. A direct relationship was found between the numbers of bacteria in the surface microlayer and the suspended particulate matter concentration.

Data on the status of summer phytoplankton of the Usariver and its tributaries are given. 184 taxa of algae with a rank lower than the genus from 7 divisions were recorded in algoflora, with Bacillariophyta (43–57% of the composition) and Chlorophyta (23–47%) predominating in the rivers. The abundance range in algocenoses was 0.02 – 5.2 mln cells/L, that of biomass was 0.01 – 1.8 mg/L; the content of chlorophyll-a was 0.01 – 3.1 µg/L. The ecological heterogeneity along the watercourse causes a significant dynamics of the taxonomic composition, which is characterized by mosaic distribution in different areas, and changes in the quantitative structure of plankton communities. An increase in the specific diversity, abundance, biomass, and chlorophyll-a concentration from the source to the mouth of rivers is noted. The ecotone effect in the zone of mixing and transformation of the waters of the lower reaches of the watercourses and the Usinsky Bay of the Kuibyshev Reservoir is expressed in an increase in the diversity and amount of algae, an increase in the coenotic role of Cyanoprokaryota and planktonic green algae of the Chlorococcales order, which are dominant in the Usinsky Bay. The influence of hydrological conditions, the content of biogens, and anthropogenic impact on the formation of algocenoses is considered. Taxonomic composition, distribution, structural characteristics of algocenoses in the absence of biogenic limiting depend on hydrological factors, biotopic heterogeneity of natural and anthropogenic origin, whereas their relation with the content of biogens in eutrophy conditions has not been revealed. TheShannon species diversity index varied from 0.5 to 2.7 bits/specimen in river algocenoses. The minimum values were noted on the upstream sections of the rivers; the complexity of the structure is typical for the algocenoses of the mixing zones of the waters of the upper part of theUsinskyBay and the mouths of the Muranka and Tisherek rivers, as well as for the communities of the sections of rivers with anthropogenic impact.

The structure of spawning taxocenoses of anuran amphibians in five floodplain lakes of the Medveditsa river valley in 2009–2018 is analysed. Two near-terrace lakes (Lebyazhye and Koblovo) and three lakes of the central floodplain (Sadok, Kruglen’koye, and Cherepashie) were used as model ones. The degradation of the populations of the three most numerous species, a decrease in the dominance degree of the common spadefoot toad were established. Degradation is more characteristic of species with a longerer distance of spawning migrations – the severity of changes consistently decreases in the row of species: Pelophylax ridibundus → Pelobates fuscus → Bombina bombina. Indices of the structure of amphibian communities in the near-terrace lakes Lebyazhye and Koblovo were stable. Against the background of low water content and unstable hydrological regime of the central floodplain lakes with a survey duration of five or more years, three periods were established to characterize the structure of spawning amphibian taxocenoses, namely: a stable structure, a sharp decrease in dominance and an increase in evenness, and an increase in the variability of the main attributes of the structure. At the end of the third period, which characterizes the structure of taxocenoses, some stabilization of the main parameters was noted with an extremely low number of mature individuals of all amphibian species. The high level of spring flood of the Medveditsa river in 2018 determined the beginning of the exit from the abnormally long period of low water content of the spawning lakes in the floodplain (from 2009 till 2017) and their functioning in the hydrological regime as temporary water bodies. The sudden increase in water content of the floodplain lakes and the extension of their hydroperiod allow the beginning of the recovery process of the population size and community structure of anuran amphibians to be noted.

The effect of gamma radiation doses of 0, 2.5, 5.5 and 7.5 Gy received by Artemia cysts on the hatching of nauplii and post-nauplial survival of crustaceans was studied at salinities of 0, 9, 18, 36, 54, 62, 78 and 88 g/L. Under the same salinities, the above parameters were also estimated without irradiation. It has been found that the rate of nauplii hatching from cysts primarily depends on salinity, the coefficient of determination being 90%. The radiation dose did not affect nauplii hatching at any salinity, except 54 g/L, when a reliable negative relationship between the hatched nauplii fraction and the radiation dose was found. The survival of crustaceans appeared from irradiated cysts depended on salinity. In the salinity range of 9–52 g/L, it was significantly less than in the range of 62–88 g/L (2.5 and 5.5 Gy). The crustaceans came from the cysts received 7.5 Gy did not survive to 12 days at a salinity of 88 g/L. The minimum postnauplial survivorship of the crustaceans was noted at a salinity of 54 g/L under all irradiation doses; this salinity can be considered as critical for artemia, when the osmoregulation mechanism reconfigures. Ecological effects in artemia populations can occur, starting from the dose of 2.5 Gy. The studied radiation doses may have long-term consequences for artemia populations in hypersalinated water bodies. To correctly quantify the effect of these doses on artemia populations, it is necessary to study not only the generation of crustaceans immediately hatched from irradiated cysts, but also 2–3 subsequent generations.

The paper is devoted to studying of the relations between the formation of “private” hunting grounds, the increase in the density of ungulates and the decline in the numbers of wolves, and the role of other factors determining the abundance of these game animals. Six ungulate species constantly live in the Saratov Region, namely: the elk (Alces alces L.), the red deer (Cervus elaphus L.), the axis deer (Cervus nippon Temminck), the roe deer (Capreolus capreolus L.), the Tartarian roe (Capreolus pygargus Pallas), and the wild boar (Sus scrofa L.). All these species, except thered deer, are commercial. The roe deer is a rare species listed in the Red Data Book of the Saratov Region. The population dynamics of the ungulates and wolf in the described region was studied using winter field records and official data on animals shooting for the period from 2001 till 2018. The abundance of all the ungulate species for this period has increased significantly, whilst the numbers of wolves, on the contrary, have decreased. The influence of several factors, both natural and anthropogenic, on the population dynamics of the mentioned species was analyzed. First of all, the impact of official hunting on the game species was considered. Of all the factors examined, only one influenced directly the population dynamics of wild ungulates in theSaratov region at the beginning of this century. The very strong direct correlation between the increase in the area of hunting grounds assigned to private hunting managers, and the increase in the numbers of wild ungulates undoubtedly speaks for their causal relationship.

With the urban-type settlement Stepnoe as an example, biodiagnosis of the soil of a settlement with low technogenic impact was conducted. In the course of our work, 30 soil samples were plated onto solid nutrition media to evaluate the following: the total numbers of heterotrophic microorganisms – on meat peptone agar, the numbers of hydrocarbon-oxidizing and iron-oxidizing microorganisms – on their corresponding selective media, and the activity of several soil redox and hydrolytic enzymes (dehydrogenases, catalases, peroxidases, and invertases) were also studied. To characterize the degree of anthropogenic impact on the soil, the content of the mobile forms of copper, zinc, lead, cadmium, chromium and nickel was evaluated and the total soil contamination coefficient (Z_c) was calculated. Within the studied area, an excess over the MPC of the mobile forms of Ni, Cu and Pb was found. In general, the values of the total soil pollution coefficient did not exceed 16 units, indicating a favorable environmental and geochemical situation in the territory of the settlement. Analysis of the total numbers of heterotrophic microorganisms, numbers of hydrocarbon-oxidizing and iron-oxidizing microorganisms, revealed deviations from the norm in certain regions of the territory surveyed, indicating an anthropogenic transformation of the soil biocenoses. The maximum deviations were typical for the index of hydrocarbon-oxidizing microorganisms, which indicated soil contamination with hydrocarbons. Our results of evaluation of the activity of indicator soil enzymes did not exclude possible functional damages in the soil. It was found that the activity of soil dehydrogenases and invertases corresponded to low and very low levels of soil enrichment with these enzymes. At the same time, the activity of soil catalases and peroxidases corresponded to the average and high levels of these enzymes, which indicated the absence of pathological changes in the soil. It has been shown that the studied soil microbiological and biochemical parameters are promising for soil health biodiagnosis in territories with low anthropogenic impact.

The results of studies conducted by the sanitary and epidemiological service in theVoronezhregion from 1959 till 2013 were analyzed. Records of small mammals (SM) were carried out by snap traps with wire hooks for baiting. Standard bait (black bread pieces flavored with sunflower oil) was used. Traps were placed in lines. The numbers of SM were calculated as a percentage of animals fallen into 100 traps per day. The data obtained were analyzed using conventional statistical methods, including the method of standard deviations. The results were considered in the territory of two regions: the Oka-Don lowland plain and the Central Russian upland in fields from May till September (the “warm” period) and in stacks and ricks from August till March (the “cold” period). It is shown that the situation in fields in the warm period and that in ricks and stacks in the cold one allow judging the future abundance of SM in these localities. It is assumed that the described trends can be used for short-term forecasting of the abundance of SM and as a justification at planning of antiepizootic, epidemiological and phytosanitary measures. One should take into account the degree of synanthropy of certain SM species and their epidemic significance. In addition, for this purpose, it is necessary to constantly carry out seasonal counts of SM in the analyzed habitats. Despite the reduction of the numbers of ricks and omets in recent years, data on the numbers of SM in these habitats are still of particular interest for analysis of the situation.

The Common hamster (Cricetus cricetus) is the rodent with one of the largest range (6 million km²). There were four phylogenetic lineages earlier recovered in Western Europe, Ukraine and Bryansk Province of Russia: “North”, “Рannonia”, E1 and E0. E1 was previously reported from South-Eastern Poland and Western Ukraine and never been found in sympatry with “Pannonia” although the closest distance between them was estimated as 20 km. The question is whether the sympatry of E1 and E0 phylogroups exists? Special survey was arranged across Moscow, Tula, Bryansk, Oryol, Kursk, Voronezh and Lipetsk provinces to get the answer. Sequence analysis of the mtDNA control region and the cyt b gene from the tissue samples was carried out in the common hamsters captured in these areas and their belonging to a certain phylogroup was determined. For the first time a case of sympatry was revealed – in the city ofMtsensk vicinity (Oryol province). Here we discovered hamsters the both lineages – E0 and E1 at the same habitat. Hypothetically E1/E0 ranges boundary runs from Ukrainian Sumy province to North-East by line dividing the Russian Kursk and Oryol provinces. The existence of subclades within both E1 and E0 phylogroups suggests that diversification of phylogenetic lineages of the Common hamster in Eastern Europe may result from not single but multiple climatic events during the second half of Late Pleistocene. The phylogeographic structure of the species inEastern Europe may be more complex than it currently known.

The content of polycyclic aromatic hydrocarbons (PAH) in Betula nаnа L. and soil organogenic horizons was studied at a control site and sites affected by a thermal power station (TPS) at distances of 0.5, 1.0, and 1.5 km from the source of pollution. The PAH distribution over the vegetative organs of dwarf birch was irregular. The qualitative composition of PAH in different organs of dwarf birch was similar. No significant changes in the PAH content in dwarf birch organs and at the surface of these organs at different distances from the TPS were revealed. The PAH content in the organs of plants affected by the TPS was 2–3 times higher than the background value, and the highest excess was found in leaves. The surface PAH concentration on the cork and roots increased by three times under contamination. No excess was revealed in leaves and branches. The excess over the background value in the soil at contaminated sites was 3–3.5 times with the maximal accumulation at a distance of 1 km. The PAH content in the soil was three times higher than that in the dwarf birch at the control site and 5–6 times at the contaminated sites. A strong correlation between the PAH concentrations in the soil and in B. nana was revealed. In the leaves and branches of B.nаnа, a decrease was revealed in the proportion of surface accumulation in the total PAH pool at contaminated sites as compared with the control site. An opposite trend was found for cork and roots. Cluster analysis showed clear separation between the surface and total PAH content in all plant organs under study. Factor analysis of the total PAH content in the organs of dwarf birch allowed us to reveal three main factors affecting the PAH distribution, with light structures, toxic components and the other polyarenes to be discerned. Dwarf birch organs can be used for indication of the contamination level in tundra communities. In order to analyze short-term changes and a long-term impact in the PAH content, we suggest using the PAH content in leaves and cork, respectively.

The paper is devoted to an important problem of modern ecology, namely, the reaction of native ecosystems to the activity of invader species, with the European beaver (Castor fiber L) as an example. This species transforms the environment as a result of its foraging and constructive activities. Higher vascular plants (macrophytes) in water bodies and streams are one of the basic components of biotopes. They serve as a limiting factor for the spread of such invasive species as C. fiber, because macrophytes determine the basis of this animal’s diet. On the other hand, under the influence of the constructive and foraging activities of C. fiber, the macrophyte communities undergo significant changes. As a result of this process, such indicators as trophicity and saprobity of natural waters change, whose quality is formed at the level of small reservoirs and watercourses. It is especially important for the forest-steppe zone characterized by relative poverty of water resources. The data collected during three field seasons (2015–2017) allow describing the current status of the highest aquatic vegetation in several small water bodies and watercourses located in the Volga regional forest-steppe State Nature Reserve. Other factors of environment transformation, such as the economic use of reservoirs and watercourses and their adjacent territories, and the recreational load, are practically excluded there. The presented data reflect the influence of C. fiber upon the biocenoses of small water bodies and watercourses.

The results of studies conducted in Romanovsky district of the Saratovregion during the period of mass flowering of Orchis militaris L. and Dactylorhiza incarnate (L.) Soo from June 2 till 16, 2017, are presented. Descriptions of habitats of the species (a hollow and a pasture), which differ in the projective cover and dominants, are given. E.g., the dominants in the hollow were Elytrigia repens (L.) Nevski, Carex vulpina L., and Potentilla anserina L, those in the pasture were Elytrigia repens (L.) Nevski, Festuca pratensis Huds., and Festuca valesiaca Gaudin. The ontogenetic structure of populations of these species is shown. E.g., in the hollow, juvenile individuals of O. militaris were absent, immature (23.1%), verginyl (34.0%) and generative individuals (42.9%) were found. In the pasture, juvenile and immature individuals of O. militaris were 6.8 and 9.3%, respectively, and verginyl (36.8%) and generative individuals (47.1%) prevailed. The age spectra of both populations are of right-sided type. In the age spectrum of the D. incarnata coenopopulation, the proportion of age groups of the pregenerative and generative periods was 52.9%. The high recovery and efficiency indices indicate a steady status of the O. militaris and D. incarnata coenopopulationss. To assess the status of these coenopopulations and further forecast of their development, annual monitoring is necessary.