As a result of our study, data were obtained on the structure of the epilithon and the physicochemical parameters of the waters in the Chusovaya river near the town of Chusovoy for 2017–2018. The taxonomic structure, quantitative characteristics, dominant species, features of the distribution of the main groups of algae were studied. The algal flora includes 191 infrageneric algal taxa (168 species) from 6 divisions, 10 classes, 24 orders, 51 families and 86 genera. The taxonomic spectrum is based on diatoms (67.5% of the total numbers), green algae (21%), and cyanobacteria (9%). In the environmental and geographical aspects, the epilithon is mainly represented by widespread salinityindifferent benthic and plankton-benthic species, having an optimum in slightly alkaline or neutral waters. The epiliton of the Chusovaya river has reached a fairly high level of development. The values of the total biomass varied from 1.46 to 46.32 g/m², and the abundance did from 1.5 to 31.7 billion cells/m². The species diversity index (an average of 3.22±0.18) indicates species-rich and balanced algocenoses of the Chusovaya river, while in summer the indices are 1.9–2.2 times lower than in autumn. The dominant algae species differed in seasons, they were represented by diatoms or cyanobacteria in terms of their number, and by diatoms in terms of their biomass. In water samples with epilithon flushing, higher concentrations of chemical substances (NH₄⁺, NO₃^-, PO₄^3-, and Fe_tot) were noted than in river water, indicating the ability of the epilithon to accumulate substances. Significant changes in the biomass and/or abundance of epilithon as a function of the content of chemical substances in water and fouling washes were revealed. By the value of the saprobity index (from 1.34 to 2.27), the sanitary-biological state of the water in the Chusovaya river is assessed as satisfactorily pure (II–III water quality classes), the saprobity zone is ο-β-, β-mesosaprobic.

30 populations of six Delphinium L. taxa (D. pubiflorum, D. litwinowii, D. duhmbergii, D. subcuneatum, D. sergii, and D. puniceum) were studied in the Ulyanovsk, Saratov, Samara, Volgograd, Astrakhan, Voronezh, Rostov, Penza and Tambov regions as well as in the Republics of Kalmykia and Mordovia in order to reveal features of their ontogenetic and vitality structures. Throughout the years of observation, the vitality of the populations of all studied species varied within rather wide ranges; individuals of medium or low vitality predominated in most populations. Also, the index of vitality of coenopopulation (IVC) varied in the populations of the same species. In over 50% of the populations, IVC was below 1. The indices of size plasticity of the species presented were rather low. The ratio of ontogenetic groups also varied substantially both among the species and among the populations of the same species. However, in most populations, generative individuals predominated; less often pre-generative or post-generative ones prevailed. According to the delta-omega criterion, most populations are mature with the only exception of D. puniceum populations being maturing at the time of observation. According to the recovery index, only few populations were capable of natural self-sustenance. Based on the results of our monitoring, it was concluded that both the number and abundance of populations of the taxa of the genus in the studied area have been dramatically decreasing in recent decades, all of them are in critical condition. This requires rigorous measures to preserve and restore the population of Delphinium species in the studied area. Without additional measures, most of the populations are doomed and can be eliminated in the near future.

Information on the functional traits of the most widespread species of freshwater zooplankton (Rotifera, Cladocera, and Copepoda) in European Russia was collected and analyzed. Our database includes 355 species described by 4 traits, namely: maximum body length, trophic group, feeding type, and movement type. Cluster analysis based on Gower's functional distances shows that freshwater zooplankton can be classified into 19 groups with different ecological roles. The characteristics of each identified functional group are presented. We believe it to be fundamentally important to build a unified classification using all available data and applicable characters for all three main taxonomic groups of zooplankton. Comparison with the existing ecological zooplankton classification proposed by Yu. S. Chuikov has demonstrated a number of advantages of our approach. Several ecological groups in Yu. S. Chuikov’s classification are represented by more fractional categories in our classification. Our system of functional groups can be used in studies of the structure of zooplanktocoenoses based on direct cluster analysis and ordination or based on functional distances between samples. To calculate the functional similarity between species, one can use our database of features, which is contained in the Appendix. Analysis based on functional groups gives a better unerstanding of the structure of a community than traditional ordination, which takes into account only the taxonomic affiliation of species. The approach used for functional group identification can be useful in assessing functional diversity and identifying patterns of freshwater zooplanktocoenoses dynamics. The database of functional signs of zooplankton can be used to check the relationship of functional signs with environmental factors.

A new method for calculating the population density of terrestrial animals, which are not amenable to individual identification, using photos or video images obtained by automatic cameras is proposed for discussion. The method is based on the continuous registration of animals on sites formed by the detection zones of camera traps with subsequent extrapolation of the results to the entire study area. A much simpler mathematical apparatus is a significant difference between our proposed method and other methods of accounting by camera traps, which allows it to be applied by a wide range of users. Both the positional measures and the scattering measures necessary for subsequent statistical analysis are calculated quite easily. Also, one of our method’s advantages is no need to know the animal movement speed, the most difficult parameter to calculate, especially in the snowless period of the year. An example of using the bootstrap method is given for the case when the input data distribution parameters do not correspond to the normal one. Using the de Moivre–Laplace theorem, the probability that the animals resting on their beds would get into the detection zone of the camera trap matrices is estimated, which is necessary for the correct use of the proposed method. Solutions are proposed for cases when this probability is low. The problems of our proposed method and their possible solutions are described. An example of calculating the density of roe deer in the open oak forest of the Khingan Nature Reserve is given on the basis of our data obtained from four camera traps.

The paper presents data on the abundance of bobak marmot (Marmota bobak Müller, 1776), obtained from 1987 till 2019. All censuses were performed according to one technique developed by us in the late 1980s. During these long-term investigations, the structure of the bobak marmot areal in the Saratov region was studied. The dynamics of its numbers is described, and its trends for individual groups of districts were revealed, distinguished by trends, the time of the appearance of new settlements as a result of reintroduction after a prolonged depression in the numbers caused by both plowing of the steppes and the well-known events of the 1920s, 1930s and 1040s, when the bobak marmot provided the survival of some part of the population. It has been established that the population peak in the indigenous settlements that have been existing from the end of the Pleistocene – the beginning of the Holocene, was in 1980–1990. New settlements arise in the territories where the marmot was reintroduced, and the species abundance continues to grow. This, first of all, refers to the western slopes of the Volga Upland and the Oka-Don plain, formerly inhabited by marmots. An increase in the numbers of the Kazakhstan subspecies of the bobak is observed at the eastern end of the Syrt plain and on the spurs of the Common Syrt in the Saratov Trans-Volga region. The genetic studies of steppe marmots by R. V. Naumov (2019) on the right Volga bank of the Ulyanovsk region showed that a genetically homogeneous population lives on the vast territory of the Volga region. This casts doubt on the assumption of the existence of the Kozlovi subspecies of the bobak marmot in the local territories of the Voskresensk, Volsk and Khvalynsk districts of the Saratov region, which served as the ground for its inclusion into the new edition of the Red Data Book of the region, which we consider unreasonable (Resolution..., 2019).

A comprehensive atomic-emission study and comparative assessment were done of the content and distribution of heavy metals (Mn, Cu, Cr, Al, Fe, Zn, and Sr) in the organs and tissues (muscles, skin, bones, gonads, liver, heart, spleen, and blood) of marsh and pool frogs collected in the lakes of a big industrial city (Nizhni Novgorod). High concentrations of heavy metals were found in the spleen (Cr), bones (Zn and Sr), liver (Cu) of lake frogs. High coefficients of the biological absorption of Mn, Sr, Zn (bone tissue), Fe (liver, spleen), and Cu (heart) were found in pool frogs. The cumulative properties of heavy metals were estimated from the accumulation coefficient established. Species regularities of heavy metal accumulation from water are presented in descending order as the following series: Zn > Cr > Al > Cu > Fe > Sr > Mn for pool frogs; and Fe > Zn > Mn > Cu > Cr > Al > Sr for marsh frogs. The priority intake of chromium, manganese, aluminum and strontium from the aqueous medium into the body occurred through the skin. Active zinc accumulation occurred mainly through food, which was confirmed by high values of the biological absorption coefficient of zinc for the liver of Pelophylax ridibundus and Pelophylax lessonae. The dependence of the heavy metal accumulation in the muscles from the organs in contact with the external environment (skin) and the digestive system (liver) was established by regression analysis. The most important adaptation of tailless amphibians is their ability to prevent excessive accumulation of heavy metals in their body, while living in the conditions of increased environmental pollution. Our results obtained speak for the high accumulation of heavy metals in the body of tailless amphibians, determined by the conditions of the aquatic environment and the bioavailability of these metals.

Hemorrhagic fever with renal syndrome (HFRS) is classifed as a most widely spread natural-focal zoonotic infection in the forest and forest-steppe regions of Russia, taking a leading position by the incidence rate among the population. The Saratov region is enzootic as regards to HFRS, but it is not included in the list of constituent entities characterized by sustainably high morbidity rates. In some years, given favorable ecological conditions, explosive growth in the numbers of the red vole (the main carrier of Hantavirus) is registered, which leads to epidemic complications. In the winter 2018– 2019season, an intensive subniveal breeding of the red vole occurred, which led to an increase in the numbers of the species in the spring. The density of such animals increased, they began to spread widely across the territory. Intensive and extensive epizooties in rodent settlements developed in the natural foci of HFRS. This was especially evident in the territory of the forest park zone “Kumysnaya Polyana”, located in the vicinity of the regional center. The numbers of rodents in ravine and floodplain deciduous forests increased everywhere and amounted to 37.6% in spring and 53.7% in autumn per 100 capture gears, which was 1.6–2 times higher than the average long-term level. The index of dominance of the red vole has also doubled and amounted to 69.5%. In general, the infection rate of rodents increased by 2-3 times in the region. This indicator in the territory of the Saratov forest park was 20.6% in spring and 35.3% in autumn. Against this background, a record outbreak of HFRS was registered in 2019, namely, 109.7 cases per 100 thousand of the population, which was ten times higher than the long-term indicator (7.2). The results of this research should be taken into account when organizing and conducting epizootiological monitoring and preventive measures in the natural foci of HFRS and other zoonotic infections.

During our field research in March–May of 2017–2020 in the valley of the Latryk river (Saratov region), it was found that the phenological norm of the beginning of the nesting period of Acanthis cannabina should be dated as the last decade of April. However, under conditions of the local climate transformation, its stability is lost and the emergence of an abnormally early start of the reproductive period of A. cannabina becomes possible. The oviposition onset of A. cannabina could be stimulated by two meteorological factors, namely, a rapid increase in the average daily temperature and, to a greater extent, an increased intensity of ultraviolet radiation in the spring.