Home – Home – Jornals – Contemporary Problems of Ecology 2026 number 1

An ecological explanation is proposed for the prevalence of eicosapentaenoic acid (20:5n-3, EPA) in the lipids of primary producers in aquatic ecosystems, such as diatoms, and of alpha-linolenic acid (18:3n-3, ALA) in the lipids of primary producers in terrestrial ecosystems, specifically seed plants. Photosynthetic membranes are unique due to the presence of conical non-bilayer lipids, monogalactosyldiacylglycerols (MGDG), which are absent in both other plant cell membranes and animal cell membranes. The non-bilayer properties - specifically, the ability to form an inverted conical shape - of MGDG molecules are conferred by the acyl chains of polyunsaturated fatty acids (PUFA). When saturated chains are present, these molecules transform into regular cylindrical bilayer lipids. As structural lipids, MGDG determine essential physical and chemical properties of membranes, often collectively referred to as “fluidity”. These properties include molecular rotation rate, diffusion, permeability, free volume, packing defects, lateral pressure, and curvature stress, all of which influence the effectiveness of membrane protein function. The primary ecological feature of diatoms and other marine and freshwater algae of the “red” evolutionary line, which distinguishes them from green plants, is their ability to photosynthesise under rapid changes in light intensity. This occurs both during their circulation in the mixed surface layer of the water column and throughout the tidal cycle in the littoral zone. The common strategies for light adaptation in green plants - such as changes in chloroplast morphology and alterations in the number and structure of light-harvesting complexes and their antennae - are too slow for these dynamic conditions. Instead, light adaptation in diatoms is achieved through the rapid operation of the xanthophyll cycle (XC) and non-photochemical quenching. These processes occur several times faster than their counterparts in members of the “green” evolutionary line. The presence of a sufficient amount of conical non-bilayer structural lipids, specifically MGDG, is crucial for the effective functioning of the XC, as it facilitates the solubilization of xanthophylls and the incorporation of de-epoxidase into the membrane. It is likely that EPA within MGDG in diatoms plays a key role in the rapid operation of the XC by conferring the structural lipid molecules with the necessary inverted conical shape. This shape cannot be fully achieved by the less unsaturated shorter chain of ALA.

In recent decades, many freshwater and coastal marine ecosystems have experienced increased inputs of chromophoric dissolved organic matter (CDOM) of terrestrial origin, primarily humic substances (HS). This phenomenon, commonly referred to in English-language literature as brownification, involves the darkening of water bodies due to elevated concentrations of colored organic compounds. The influx of HS into aquatic systems alters the optical, chemical, and trophic characteristics of the water column. This interdisciplinary review synthesizes current scientific knowledge on the effects of humic substances on phytoplankton primary production, trophic structure, and community composition under conditions of climate change. Key mechanisms are examined, including reduced light penetration, enhanced thermal stratification, nutrient transport, and the involvement of HS in redox processes. Evidence suggests that moderate humification can stimulate productivity through microbial degradation and photodecomposition of allochthonous organic matter, releasing additional nutrients. However, at high HS concentrations, photosynthetic activity declines, phytoplankton shift toward mixotrophy, and biodiversity decreases. Altered light spectra favor groups with accessory pigments and vertical mobility, such as cryptophytes, dinoflagellates, and cyanobacteria, potentially reducing ecosystem trophic efficiency. Ecosystem responses to humification vary with geographic, climatic, and morphometric characteristics of water bodies. Special attention is given to boreal and Arctic regions, where permafrost thaw and increased precipitation intensify HS runoff. Key research directions are identified, including thresholds of abrupt change, the role of mixotrophy in carbon cycling, and the development of region-specific adaptation strategies. The review underscores the importance of an integrated approach to assessing the ecological consequences of aquatic humification.

The results of DNA barcoding of Tubifex tubifex from various freshwater bodies within the Vychegda River basin (Komi Republic, Russia) are discussed. A molecular genetic analysis of 32 specimens collected from 14 locations, based on nucleotide sequences of the mitochondrial cytochrome c oxidase subunit I (cox1) gene fragment, revealed six distinct lineages (A, B, C, D, E, J) exhibiting inter-lineage divergence exceeding 17-24 %. A significant correlation was identified between the genetic diversity of the species and habitat characteristics, including hydrological and hydrochemical parameters of water and sediments. The observed ecological differentiation supports the presence of heterogeneous adaptive traits within T. tubifex and highlights the importance of considering population genetic structure in ecological assessments of freshwater ecosystems.

The article analyzes retrospective literature data and the results of our own research on ichthyoplankton in the coastal waters of southeastern Crimea (the waters of the Karadag Nature Reserve) over the period 1950-2024. Samples were collected in the coastal zone using vertical and horizontal surface fishing methods. Information on taxonomic composition, structure, and abundance dynamics of ichthyoplankton are presented. During a 70-year research period, eggs and larvae of 66 fish species from 33 families were identified. The recovery of ichthyoplankton abundance and species composition after the collapse of the Black Sea ecosystem in the 1990s occurred against the background of climatic changes that significantly impacted the hydrological regime and thermohaline structure of waters in the Azov-Black Sea Basin. In recent years, there has been an increase in the number of species, including due to the introduction of Mediterranean species, and a change in the dominance and sub-dominance of species has occurred.

Structural and functional characteristics of plankton communities are widely used as ecological indicators of global ocean warming. In terms of long-term variability, they indicate the existence of monotonous negative, positive and “zero” trends, i. e. their absence. The latter can be considered as phenomena of regional resilience of plankton communities to global warming. Based on the materials of regional sampling and international databases, an analysis of the interannual variability of zooplankton biomass and indices of its species diversity in the Arabian, Mediterranean and Black seas (from 2000 to 2023) was carried out. For comparison, data on biomass measurements in five other regions of the Atlantic and Pacific Oceans were used. It is shown that the duration of the existence of phenomena of regional stability of plankton communities ranges from several to tens of years, in a wide range of species diversity and biological productivity of waters. In most of the studied regions, the absence of interannual trends in zooplankton biomass corresponded to their absence in the interannual variability of chlorophyll a concentration as an indicator of phytoplankton biomass. Such a correspondence indirectly indicates a trophic basis for the interannual stability of zooplankton biomass.

The present study addresses seasonal dynamics of the abundance, size-age composition, and production of the larvae of the caddisfly Apatania crymophyla McLachlan, 1880, which form high-density aggregations on water moss in the thermally and hydrologically altered section of the Yenisei River downstream of the Krasnoyarsk Hydroelectric Plant dam (HEP). The abundance of the larvae inhabiting water moss was highest in October 2022 and 2023 and in August 2021. The maximal abundance of the larvae on moss varied between 1242 and 4037 ind.·kg^-1 of fresh moss, and the fresh biomass of the larvae varied from 1.78 to 3.15 g·kg^-1 of fresh moss. The level of water in the river affected the quantitative parameters and the number of generations of A. crymophila. In the 2022, when the water level was abnormally low, the number of new generations in the population was smaller and the production of the larval biomass over the season was lower (by a factor of 1.8) than in 2023, when the water level was close to the long-term annual average. Hence, the conditions in the thermally altered section of the Yenisei River downstream of the Krasnoyarsk HEP are favorable for the development of A. crymophila; one of these conditions is the abundance of aquatic moss in this section, which provides the invertebrates with resources favoring the maintenance of the high-density population. The results obtained show that the invertebrates inhabiting aquatic moss should be taken into account in the estimate of organic matter production in the Yenisei River.

The peculiarities of reproduction and population structure of the northern red-backed vole in the northern taiga of Western Siberia are considered. Rodent trapping was carried out in the snowless period using the method of ditch with pitfalls (guide fences made of polyethylene film) and trap-lines. A total of 2704 northern red-backed vole were recorded in the southern strip of northern taiga over a 9-year period and in the northern strip of northern taiga over a 4-year period. The reproductive participation of females was determined by the presence of embryos and placental scars, the participation of males by the presence of spermatozoa in the epididymis and the size of the testis. The age of voles was determined by M² root development, and mass, body length, and thymus development were used. Adult overwintered voles have a reproductive period of up to five months, and up to three months for young voles. Overwintered males remain sexually active throughout the entire snowless period. Overwintered females of the southern strip bring three litters, and young females two litters. Most overwintered females in the northern strip bring two litters, and in rare cases a third litter is possible, while young females bring two litters. In the southern strip in April-May, and in the northern strip in June, the northern red-backed vole population is represented exclusively by overwintered animals. In August and September are universally dominated by young. Males predominate among adults and young animals, only in late summer and autumn the numerical advantage is shifted towards females among overwintered animals.

The plague microbe (Yersinia pestis) is unique in the family of pathogens of intestinal infections of the family Yersiniaceae (Enterobacteriaceae) and the genus Yersinia. This is the only species of the family and genus that, in natural conditions, is transmitted in rodent populations not by an alimentary route, as typical intestinal pathogens, but by a transmissible way through flea bites, which indicates some unique circumstances of its speciation. Such a special circumstance was the wound infection in populations of the Mongolian marmot (Marmota sibirica) with the causative agent of pseudotuberculosis of the 1st serotype (Y. pseudotuberculosis O:1b) or, in other words, Far Eastern scarlet-like fever (FESLF). The abiotic trigger for speciation was the maximum Sartan cooling, which covered vast areas of Central Asia at the turn of the Pleistocene and Holocene, 22-15 thousand years ago. Deep freezing of the ground in the settlements of the Mongolian marmot led to a change in the behavior of the larvae of the marmot flea Oropsylla silantiewi - a transition to hematophagy on marmots during hibernation, which caused a massive penetration of the FESLF pathogen into the blood of marmots through wounds on the mucous membrane in the oral cavity, created by flea larvae. Aberrant resistant wound infection of marmots with FESLF caused change in gene flow and speciation of Y. pestis. According to the optimistic version of the environmental scenario, the speciation process took place autonomously in three geographical populations of marmots; almost simultaneously, three initial microbial subspecies 2.ANT3, 3.ANT2 and 4.ANT1 appeared, which later became the basis of the entire world intraspecific diversity of this pathogen.

The results of parasitologic and metagenomic study of two nests of the long-tailed gopher obtained in the Tuva mountain plague focus (Mongun-Taiga kozhun of the Tyva Republic) are presented. The fauna of blood-sucking arthropods of both nests was formed by fleas Citellophilus tesquorum Wagn., Frontopsylla elatoides Wagn., Rhadinopsylla li transbaikalica Ioff et Tifl., Oropsylla alaskensis Baker, Neopsylla mana Wagn. and ticks Haemogamasus mandschuricus Vitzthum and Hg. hodosi Goncharova et Buyakova. F. hetera Wagn., F. frontalis baikal Ioff were sporadically present in nest No. 1. According to the size, depth of occurrence, length of passage to the nest chamber, species composition and physiological state of ectoparasites, nests were defined as wintering nest No. 1 and reserve nest No. 2. According to the results of metagenomic analysis, nest community No. 1 contained 64.2 % of Proteobacteria phyla (Allorhizobium - 22.8 %, Aureimonas - 9.71 % and Methylobacterium - 7.68 %), 35 % of Actinobacteria (including Brachybacterium - 3.8 %, Amycolatopsis - 3.33 %, Brevibacterium - 1.76 %), 0.8 % of Firmicutes (Staphylococcus). In the sample from nest No. 2, 87.1 % of sequenced sequences belonged to Actinobacteria phyla (Brachybacterium - 51.0 %, Brevibacterium - 19.6 % and Nocardioides - 7.4 %), 12.8 % to Firmicutes (Staphylococcus), 0.08 % to Proteobacteria (Methylobacterium). Possible reasons for the differences in the composition of nest bacterial communities are discussed.

Extreme weather events change the diurnal and seasonal variations in CO₂ fluxes between the forest and the above surface atmosphere. The analysis of interannual variability of net CO₂ exchange (NEE), total ecosystem respiration (TER), gross ecosystem photosynthesis (GEP) and evapotranspiration (ET) in a cowberry-lichen pine forest of the middle taiga subzone was performed under different weather conditions during the 2021-2023 growing season. According to measurements by eddy covariance system, in the pine forest over three years of observations, the total NEE in May-August varied from -653 to -980 g CO₂/m², GEP varied from 1711 to 2360 g CO₂/m², TER - from 913 to 1380 g CO₂/m². The total evapotranspiration corresponded to 137-262 mm, and the GEP/ET ratio varied within 1.8-3.9 mgC/g H₂O. As a result of multi-level statistical analysis, a correlation GEP with gross radiation, temperature and humidity in the growing season was revealed. A relationship between GEP and air temperature and humidity characteristics of the growing season was revealed. GEP and NEE decreased at abnormally high temperatures and a long absence of precipitation in the first half of the 2021 growing season. Maximal effect of air temperature on ecosystem CO₂ exchange was observed in 2023 at increased supply of soil moisture. It was concluded that the water reserve in the soil mitigates the negative effect of atmospheric moisture deficit in the summer on photosynthesis and evapotranspiration and thereby ensures a stable seasonal net sink of CO₂ in the ecosystem of the cowberry-lichen pine forest of the middle taiga subzone.

Understanding the relationship between the conditions prevailing in anthropogenic altered soils and the diversity of the soil microbiome can provide important information for assessing the state and solving the problem of maintaining the stability of natural and man-made ecosystems. Using high-throughput Illumina sequencing, the diversity and composition of bacteria, archaea, and fungi in the soils of five different phytocenoses within the Meshcherskaya Lowland (Southern Moscow region), as one of the most industrially saturated regions in the country, were analyzed. The results showed a reduction in taxonomic richness and a decrease in phylogenetic diversity and alignment of microbial communities during the transition from the soil of a conventionally background site to soils of secondary phytocenoses and soils associated with man-made objects - an overgrown phosphogypsum dump and an industrial wastewater discharge site. Representatives of 28 bacterial and 1 archaeal phylum were identified in the prokaryotic component of the microbiomes of the studied soils. The dominant position was occupied by the phylum Actinomycetota (relative abundance 21-30 %) and Pseudomonadota (16-19 %). The taxonomic composition of the fungal component of the communities was dominated by Ascomycota (53-74 %), represented by the classes Dothideomycetes, Sordariomycetes, Eurotiomycetes, and Leotiomycetes. Representatives of Basidiomycota in the soils of different phytocenoses accounted for from 16 to 29 % of all identified fungal taxa. The most numerous among the basidiomycetes were the classes Tremellomycetes, Agaricomycetes, and Microbotryomycetes. Using the FAPROTAX software package for predicting the ecological functions of bacterial and archaeal taxa obtained by sequencing 16S rRNA amplicons, as well as the automatic FUNGuild algorithm for sorting by ecologically significant categories of the fungal taxa identified during ITS amplicon sequencing, the ecological profiles of the studied microbial communities were characterized. The data obtained can be used in the environmental monitoring system of impact zones of industrial enterprises.

Biosorption is a promising method for preventing REE migration in natural environments and for their purification, and microscopic fungi are considered effective biosorbents. The article is devoted to studying the biosorption capacity of soil microscopic fungi in relation to REE in aqueous solutions. The dyna`mics of adsorption was studied using the example of lanthanum by the biomass of micromycetes Penicillium canescens and Talaromyces funiculosus depending on the contact time and its concentration in the solution. It was found that adsorption equilibrium in the fungal biomass - aqueous lanthanum solution system occurs within 24 hours, the T. funiculosus biomass demonstrated a higher sorption capacity. Lanthanum adsorption is more intense at medium acidic pH values of solutions; the maximum lanthanum sorption for 24 hours was noted at pH 3.1 by P. canescens biomass. It was revealed that REE with larger ionic radii are extracted more effectively, they more actively occupy free sorption centers with the formation of complexes. With prolonged interaction of REE with fungal biomass, nanoparticles are formed, the composition of which is close to monazite. According to IR spectroscopy data, the REE sorption centers are amide, carboxyl, amine and phosphate groups of the fungal cell wall. The presence of many ionogenic groups determines the high sorption capacity of the fungal cell wall. Intermolecular modeling of the interaction of lanthanum with amino acid residues of fungal cell wall proteins revealed that proteins form strong complexes by complex formation of REE with amino acid residues, where the active centers are glutamic and aspartic amino acids.

Based on the results of microbial indication for 2023 and 2024, it was established that Avacha Gulf and the southwestern coast of Kamchatka are subject to significant oil pollution. The number of hydrocarbon-oxidizing microorganisms at most of the studied stations was 10³ CFU/ml (g) and higher. The results of molecular genetic analysis identifying marker bacterial genes for the oxidation of alkanes (ALK-1, ALK-2, ALK-3) and PAHs (nah, phn, bphA1, xylE, GN-PAH, GP-PAH) in the environment indicated the dominance of bacteria capable to oxidize short- and medium-chain alkanes in the surface waters of Avacha Gulf in 2023, and bacteria that are potential destructors of medium- and long-chain alkanes in the waters of the southwestern coast of Kamchatka. Also, the waters of both areas were characterized by a significant presence of gram-negative bacteria that oxidize various types of PAHs. In 2024, the proportion of stations with bacteria that degrade phenanthrene and short-chain alkanes sharply decreased in Avacha Gulf, but the proportion of stations with microorganisms that oxidize long-chain alkanes increased. An increase in the proportion of water samples with bacterial biphenyl oxidation genes and PAH oxidation genes of gram-negative microbiota was noted for the southwestern coast of Kamchatka. In bottom sediment samples collected in 2023 from both study areas, the genes responsible for PAH oxidation by gram-positive microbiota and for the degradation of long-chain alkanes were most often detected. Analysis of bottom sediment samples collected in 2024 indicated a decrease in the proportion of stations with microorganisms capable of oxidizing various petroleum hydrocarbons in both study areas.

The accidental diesel fuel spill near the city of Norilsk in 2020 served as the basis for studying the behavior of hydrocarbons in Far Northern soils, which are characterized by a low rate of natural self-purification. The objective of this study is to determine the direction of transformation in the composition of diesel fuel hydrocarbons in various soil types, which is important for optimizing remediation measures for petroleum pollution in the Arctic zone of Russia. Using gas chromatography-mass spectrometry, the distribution of diesel fuel components - including normal and isoprenoid alkanes, alkylcyclohexanes, bicyclic naphthenes, alkyl-substituted benzene derivatives of normal and isoprenoid structures, naphthalenes, and phenanthrenes - was analyzed in Arctic soils differentiated by distance from the spill site and time elapsed since the accident. Differences in hydrocarbon composition in the vertical soil profile were identified, reflecting the pathways of contamination and the specific soil types. In sandy and waterlogged alluvial-gley soils near the spill site, downward percolation of diesel fuel led to an increased proportion of high-molecular-weight and branched hydrocarbons, attributed to exclusion chromatography effects during filtration through the soil. Transport of diesel fuel along the watercourse resulted in the loss of low-molecular-weight members across all homologous hydrocarbon series due to leaching and evaporation during aquatic migration. The deposition of residual diesel components in floodplain sod-alluvial-gley soils was accompanied by mixing in the upper soil layers, while the lower profile showed accumulation of isoprenoid alkanes, alkylbenzenes, bicyclic naphthenes, naphthalenes, and phenanthrenes with a higher content of low-molecular-weight fractions. One year after the diesel fuel entered the watercourse, redistribution of contaminants was observed in the floodplain sod-alluvial-gley soil profile under the influence of seasonal hydrodynamic processes, including the influx of a new portion of pollutants during spring floods. Traces of the initial contamination persisted only in the deeper soil layers.