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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 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.

As a result of studying the collections of Herbariums ABG, LE, MW, MHA, NSK, NS, TK, ALTB, as well as their own expedition collections, information about the species composition of the genus <i>Geranium</i> L. in the flora of the Republic of Kazakhstan has been clarified. For the first time, the species <i>G. transbaicalicum</i> Serg was identified in the flora of Kazakhstan. The ranges of <i>G. affine , G. asiaticum , G. collinum , G. divaricatum , G. pratense , G. sergievskajae , G. pseudosibiricum, G. pusillum , G. robertianum , G. schrenkianum , G. sibiricum , G. sylvaticum , G. transversale , and G. turczaninovii</i> species in Kazakhstan have been supplemented. The lectotype of <i>G. regelii</i> Nevski is designated. A key has been compiled to identify the species.

The freshwater benthic alga Hydrurus foetidus (Villars) Trevisan was first found in the Iy-Khem River in the Todzha Basin of the Tyva Republic. Geographically, the species is widespread, but it usually grows only in cold waters. The recorded occurrence of H. foetidus in waters with a temperature of 20-21 °C significantly expands our understanding of the ecological distribution of this species. The first discovery of the species in the waters of the Todzha Basin adds to our knowledge of the diversity of algae in the Tyva Republic.

The flora of Omsk Region remains insufficiently and unevenly studied. This is confirmed by numerous findings made during floristic research, which determines the relevance of continuing flora inventory work. The article presents the results of studies of the vascular plant flora of the region for the period 2013-2024. The work was carried out within the framework of the “Flora of Asiatic Russia 2.0” project and is based on field data and verified observations from the iNaturalist platform. For the first time in the region, 28 species and 5 hybrids have been identified, of which 12 species and 4 hybrids are native, while 16 species and 1 hybrid are adventive. Among adventive species, ergasiophygophytes (11 species) predominate, while by degree of naturalization, epecophytes (6 species), ephemerophytes (4 species), colonophytes and ephemerophyte-epecophytes (3 species each) are distinguished. Additional studies are required on the distribution of Sorbus aucuparia L. and Leucanthemum ircutianum DC. in the region. Widely cultivated species ( Cucurbita maxima Duchesne, C. pepo L., Solanum lycopersicum L., S. tuberosum L.) occasionally become wild and persist for a short time near cultivation sites (garden plots, individual residential areas) and landfills. Four rare species have been proposed for inclusion in the Red Book of Omsk Region: Dianthus krylovianus Juz., Astragalus lagobromus Knjaz. & Kulikov, Bupleurum aureum Fisch. and Eremogone koriniana (Fisch. ex Fenzl) Ikonn . The study results significantly expand the known vascular plants flora of Omsk Region, this is of great importance for biodiversity conservation and planning of environmental protection measures.