During our route surveys, few habitats of Heracleum mantegazzianum Sommier & Levier were identified in the Karachay-Cherkess Republic and Krasnodarsky region. Analysis of climatic data have shown that within its native range in the Western Caucasus, the optimal conditions for the growth and development of this species occur at elevations ranging from 700 m to 1300 m asl. The limiting factors for its dispersal are the duration of the period with stable snow cover and snow depth, which determine the possibility of seed stratification and the risk of cold damage to overwintering plant organs. In its natural habitats in the Caucasus, such plants occur singly or in groups of up to 30–50 individuals. In disturbed habitats, the species forms monodominant stands with foliage projective cover close to 100 %. Plants enter the reproductive phase at the age of 2 to 4 full years. The height of generative H. mantegazzianum individuals reaches 3.5 m, and the mass of the largest plants ranges from 11 to 20 kg, which is comparable to the characteristics of individuals of this species in its invasive range. Voucher specimens of H. mantegazzianum collected in the Western Caucasus are deposited at the SYKO scientific herbarium (https://ib.komisc.ru/add/herbarium).

   The article presents the results of our study on the dynamics of a forest ecosystem type extremely rare in the central Volga Upland, namely, wet sudubrava (C4). The study was conducted in the Upper Sura section of the State Nature Reserve “Privolzhskaya Lesostep”. The process was examined in an age series identified in homogeneous forest growth conditions based on the principles of dynamic classification of forest types. Forest inventory data were processed to obtain average values of forest stand taxonomy indicators for each age class. Changes in all stand components were analyzed simultaneously. Based on this analysis, the age series was divided into individual periods and phases. Trends in the share of each forest-forming species in the stand composition at different age stages are described by nonlinear equations. It is shown that the resulting age series represents a transformation series of forest communities. Disruption of the forest formation process led to a large-scale replacement of native stands with derivatives. After the introduction of clear-cutting, the area occupied by deciduous trees steadily increased. The large-scale use of intermediate, sanitary, and voluntary selective logging resulted in the formation of thinned pine stands. Concurrently, the lower layers of communities were transformed. These factors worsened the conditions for natural regeneration of pine (Pinus sylvestris L.). As a result, the formation of pine stands through natural regeneration is now greatly hampered.

   Analysis of the growth characteristics of individuals and the parameters of the anchovy population living on the south-western shelf of the Crimea under conditions of sea surface temperature (SST) changes in 2000–2020 has been performed. The material for our research was the catches of anchovy by trawls on few fishing vessels on the south-western shelf of the Crimea during the wintering period (November–March). Linear SST trends on the south-western shelf of the Crimea were estimated. The average annual SST increase in 2000–2020 was 0.055 °C. It is shown that the 20-year period can be roughly divided into three periods according to the nature of SST changes, namely: 2000–2007 (I period), 2008–2013 (II period), and 2014–2020 (III period) according to the SST change rate inside each of them. In the warmest period (2014–2020), compared with 2000–2007, the average length of the anchovy increased by 5 %, the average weight by 15 %, and the average anchovy age in catches by 1.2 times, respectively. There was an increase in the rate of linear and weight growth in periods II and III relative to period I. A positive correlation (Pearson’s correlation coefficient r = 0.89) between the increase in the average annual SST and the maximum anchovy length has been confirmed. In the period of 2000–2020, the proportion of older age groups for anchovy catches on the south-western shelf of the Crimea increased, which led to an increase in the proportion of larger, well-fed individuals living on the south-western shelf of the Crimea, to an increase in the average size and weight of fish. It is assumed that the increase in the average annual SST in 2000–2020 had a positive impact on the development of anchovy, which belongs to the thermophilic fish complex.

   The hemoparasite invasion and immunophysiological status were assessed in 63 Pelophylax ridibundus individuals from three aquatic habitats in the Middle Volga region. Hydrochemical analysis of the frog habitats revealed that the maximum permissible concentrations of manganese, copper, chromium, zinc and cobalt compounds were exceeded in the fisheries-designated waterbodies. According to the Specific Combinatorial Water Pollution Index, the water quality classes corresponded to Class 4 (very polluted, Category G) and Class 5 (extremely polluted). High hemoparasite prevalence was established (58.7 % of individuals). Intracellular parasites of the class Conoidasida (representatives of the genus Dactylosoma from the family Dactylosomotidae, representatives of the genus Hepatozoon from the family Hepatozoidae) and extracellular parasites (class Nematoda, family Onchocercidae, microfilaria larvae) were identified in blood smears. Representatives of the genus Dactylosoma were found in the most infected individuals. Sex-specific differences in the infection indices were observed across the habitats. Hemoparasite infection was associated with decreased levels of large circulating immune complexes (CIC) and reduced large-to-small CIC ratio (aggregation index). Infected frogs exhibited elevated eosinophil counts and altered comprehensive leukocyte indices, namely: karyopyknotic index, lymphocyte-granulocyte ratio, lymphocyte-to-eosinophil ratio, and leukocyte shift index, indicating activation of their antiparasitic defense. Infected females showed a differential relative mass of the internal organs (heart, liver, kidneys, gonads – but not spleen) compared to uninfected individuals. In males, hemoparasite infection reduced their cardiosomatic and renosomatic indices, while exposure to extremely polluted water increased the hepatosomatic and gonadosomatic indices.

   Soil protection from pollution and restoration of their natural functions is the most important task of sustainable development. Currently, scientists from different countries are actively conducting research aimed at finding the best technologies for remediation of contaminated areas. Bioremediation technologies that involve the use of various microorganisms (MO), in particular bacteria, for the destruction or inactivation of pollutants can be very promising in this direction. Bacteria have a very flexible genetic apparatus. Due to the mutation process, new genes appear in the genome of these MO, allowing not only to survive in a polluted environment, but also to use xenobiotics to obtain energy and plastic substances. Bacteria belonging to the types Firmicutes, Proteobacteria, Actinobacteria and Cyanobacteria can be of the greatest interest as bioremediation agents. Effective strains of these bacteria are able to inactivate heavy metals, destroy petroleum hydrocarbons, aromatic compounds, pesticides, pharmaceuticals, dyes, synthetic polymers and other pollutants. Metabolic capabilities of bacteria can be expanded and enhanced by editing their genome and creating artificial self-regulating consortia, including symbiotic MO implementing different metabolic pathways. A serious obstacle to the widespread introduction of bioremediation technologies into practice is the insufficient stability and viability of strains grown in bioreactors in the natural environment. The use of the latest achievements in genetic and cellular engineering, intelligent materials, the possibility of targeted delivery of destructor microorganisms and intelligent monitoring can contribute to increasing the stability and efficiency of microbial technologies.

   This article presents the temporal organization of springtail communities in tundra ecosystems across the European Russia. These ecosystems share similar climatic conditions but vary in vegetation type, permafrost occurrence, and soil temperature. Our study included both pristine tundra and secondary biocenoses formed due to agricultural activities in the North. In the small-bush and dwarf shrub tundra, the springtail population structure remains relatively stable. This stability is indicative of long-term maintenance of the phytocenosis composition and structure, allowing us to characterize these springtail communities as structurally stable. However, in less favorable environments, such as the large-bush and cold moss-lichen tundra, the springtail communities exhibit slight fluctuations. These fluctuations are marked by an extended set of the dominant species that replace each other over time. In contrast, highly fluctuating springtail communities are characteristic of secondary biocenoses. These findings highlight the impact of environmental conditions and human activities on the stability and diversity of springtail communities in tundra ecosystems.

   The results of our analysis of the genetic structure of the steppe marmot population restored on the territory of the State Nature Reserve “Privolzhskaya Lesostep” are presented in comparison with its maternal populations for 4 microsatellite DNA loci (Xmoh C10, Xmoh D116, IGS-bp, Ssu17). Some features have been identified that indicate both the quality of the emerging composition of its population and the degree of its stability. According to the allelic spectrum of microsatellite DNA, the introduced population in the reserve is characterized by a high proportion of unique alleles, with a high level of polymorphism of its genetic structure (H_obs – 0.775, AGD – 0.739), indicating its stable state and no nature selection. The detection of microsatellite DNA alleles not identified in the maternal populations is probably associated with the first (2014) wave of introduced animals, who successfully entrenched in their new habitat and formed the core of the future population. This conclusion is supported by data on genetic distances (Δμ²) and fixation indices (FST) of the five analyzed steppe marmot populations. The highest values of FST were obtained for the population in the reserve in comparison with other populations (0.336–0.301). Similar results were obtained for genetic distances (Δμ²). The highest distance was obtained for two geographically close populations (3.135, 1.564). Thus, the introduced population in the reserve is characterized by a specific genetic structure, which was formed as a result of multi-stage (2014, 2020, and 2021) introduction and stable isolation. The unique features of the genetic structure of the population restored in the reserve are a consequence of the artificial method of its formation. These features stand out clearly against the backdrop of poorly differentiated maternal populations of steppe marmots, which were formed through natural, dynamic population processes.

   For the first time, an individual of an extremely rare species of the cladoceran Graptoleberis smirnovi Sinev, Gavrilko, 2020 was found in the Volga–Akhtuba floodplain. The species was found in the summer in the littoral part of the Bolshoy floodplain lake, which is characterized by a high degree of overgrowth with aquatic macrophytes (70 %), high transparency (1.5 m), and water temperature (28 ºC). The abundance and biomass of Graptoleberis smirnovi were 0.5 thousand ind./m³ and 4.5 mg/m³, respectively, which accounted for 0.7 % and 1.1 % of the total abundance and biomass of the community. The size of females ranged from 420 to 550 μm.