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The purpose of this paper is to present the results of sequence stratigraphic modeling of subcontinental reservoirs of the Tanopcha Formation upper part (Lower Cretaceous) of the Minkhov field, located in the northern part of the Messov oil and gas region of the Gydan oil and gas region. The study is vital due to the need for additional exploration and commissioning of hydrocarbon reserves in the lower part of the Pokur suprahorizon in the north of Western Siberia. The modeling is based on sedimentological columns for four wells, in which the object of study was characterized by a core with sufficient completeness. The structure of seven sequences has been studied. Sequences PK 2-2, 2-3, 2-4, 2-5, 2-6, and PK 3-1, in accordance with the classical concept, are divided into three systems tracts: lowstand (LST), transgressive (TST), highstand (HST). The boundaries of the sequences are outlined along the erosive surfaces in the bottom of the alluvial complexes. LST tops - on contacts of alluvial facies with tidal, marsh, lake sediments, indicating flooding of the coastal plain at the beginning of transgressions. TST tops - on contacts of facies of the tidal plain with alluvial deposits, indicating the beginning of normal regressions. The main reservoirs of the object are large belts and covers of alluvium of amalgamating channels as part of the LST. Additional reservoirs are thin bodies of tidal genesis in the composition of TST, and alluvial genesis in the composition of HST. The bottom of the PK 3-2 sequence was outlined on the contacts of coastal-marine TST sandstones with tidal and marsh facies, indicating the event transgression of the coastline. One of the main reservoirs of the field, the TP₁ formation, is connected to the TST of the PK 3-2 sequence. The boundaries of the selected sequences can be traced on seismic sections of acoustic impedance. Depending on the temporary thickness in the impedance field, the sequences are displayed as two-, three- and four-layer sequences of layers, which opens up the possibility of their further study by the method of wave field inversion

Climate change, which causes significant structural transformations of ecosystems, is becoming one of the most acute environmental problems of our time. Monitoring observations in protected areas, where anthropogenic impacts are minimal, highlight the impact of climate on natural communities. We studied the changes in the structure of summer phytoplankton in Lake Raifskoe (Volga-Kama Reserve) and the relationships between these changes and environmental factors for more than twenty years. The study showed an increase in the proportion of dinophyte algae in the total biomass of summer phytoplankton in the studied lake situated in the forest zone. This structural change is more typical of the structure of lake communities in the forest-steppe zone. The climate, and particularly the air temperature of the warmest month (July), plays a leading role in the change in the structure of phytoplankton. The influence of climate humidity (precipitation) on the phytoplankton community was not revealed. Our data show that current climate changes lead to the rearrangement of phytoplankton communities, in which the structure of the biomass of the summer phytoplankton of the studied lake from the forest zone of the Middle Volga region can acquire features of the structure of lake communities from the forest-steppe zone.

The study of fecal compounds in lake sediments is one of the newest trends in paleo-limnology. Some stanols are produced by the intestinal microflora of animals from sterols found in food. Once in water bodies, these substances remain in bottom sediments for millennia, therefore they are biochemical indicators of fecal intake. In humans and animals, similar 5β-stanols are synthesized, but their percentages differ. The human intestinal microflora produces more coprostanol and epicoprostanol compared to other animals, so these 5β-stanols are used to reconstruct the history of the population of water bodies, as well as to assess the anthropogenic load. In the present work, using gas chromatography with mass spectrometric detection, the vertical distribution of fecal stanols and their precursor cholesterol in dated bottom sediments of Lake Shira (southern Siberia, Republic of Khakassia) for a period of about 2000 years was studied for the first time. It is shown that the relative share of coprostanol and epicoprostanol was higher in sediments corresponding to the periods when the anthropogenic load in the lake′s drainage basin was supposedly increased: during the heyday of the medieval state of the Yenisei Kyrgyz (9-11 centuries AD), during the period of mass colonization by the Russian population (17-18 centuries), as well as in the 19-20 centuries during the development of resort activities. The absolute content of all fecal stanols during the last hundred years is higher, which can be explained both by an increase in fecal inflows and by degradation of stanols, leading to a decrease in the content of fecal stanols in the underlying core layers. The results obtained can be useful for monitoring the efficiency of treatment facilities, as well as for identifying the historical dynamics of human presence in the lake′s catchment area.

The industrial chemicals alkylphenols are xenoestrogens, but the sublethal effects of these substances on aquatic animals are poorly studied. The aim of this work was to study possible metabolic and reproductive disorders in amphipods, on the example of the species Gmelinoides fasciatus from the Gulf of Finland of the Baltic Sea, after experimental exposure to 4- tert -octylphenol (4t-OP) from the group of alkylphenols. The mortality of G. fasciatus amphipods in the 4t-OP concentration range from 0.5 to 1000 μg/L after 96 hours and 7 days increased with increasing concentration. It was absent at 4t-OP concentrations of 0.5 and 5 μg/L. At a concentration of 4t-OP of 20 μg/L, after 7 days, the mortality of crustaceans was 20 %, and at its concentration of 100 μg/L, it was 60 %. When exposed to sublethal concentrations of 4t-OP (0.5 μg/L), these amphipods showed a decrease in sexual activity after one week of amphipods: only 25 % of amphipods retained precopulatory pairs versus 100 % in control. Under chronic exposure (28 days) to the lowest concentration, males showed signs of demasculinization (decrease in the width of the gnathopods and an increase in the depth of the coxal plates); females showed a decrease in the overall fecundity and irreversible disturbances in state of embryos, namely, a high proportion (>50 %) of embryos that stopped their development at different stages of organogenesis. The conducted study shows significant functional disorders of metabolic processes and reproduction in crustaceans even when exposed to non-lethal concentrations of octylphenol. These results confirm the high toxicity of this industrial pollutant, the presence of which in the aquatic environment can lead to irreversible changes in the biota.

Non-indigenous brown bullhead from two lakes of the Karelian Isthmus was studied in relation to 36 morphological features characterizing the shape of the body and head, the position of the fins, the number of finrays and vertebrae. The obtained results were compared with data for the collection materials and earlier published data for other parts of the species distribution range in order to assess the intraspecific differentiation and morphological plasticity of this invasive species. Meristic characters of individuals from geographically distant sites were quite similar and no difference between areas was found. On the contrary, significant differences in morphometric characters between samples from geographically remote water areas of Europe were shown, reaching the thresholds established for subspecies identification. The high level of morphometric variability in the invasive brown bullhead indicates a high phenotypic plasticity in external morphological traits responsible for fish locomotion, which is considered among factors contributing to its successful adaptation to new habitats and determining the invasive potential of this species.

Studies of the physiological state of three-year-old pikeperch from the lake (natural habitat), ponds and fish farm cages, showed significant differences in the size, mass, biochemical, hematological and histophysiological parameters of fish. Farmed fish have large sizes (length 26.2 cm, weight 242.1 g), comparable to the size of lake individuals (27.6 cm and 278.2 g, versus 23.7 cm and 162.6 g in pond pikeperch), high liver index values (3.68 versus 1.42 and 1.03 % in lake and pond fish, respectively), gonads (0.73 versus 0.15 and 0.08 %) and abdominal fat (8.61 versus 1.87 and 2.30 %). The chemical composition of the body of farmed fish is characterized by a large amount of lipids (9.4 versus 2.5 and 3.6 %, respectively) and nitrogen-free extracts (3.4 versus 2.5 and 2.4 %), muscle - protein (21.0 versus 19.0 and 19.2 %), liver - lipids (26.6 versus 11.1 and 7.5 %, respectively) and nitrogen-free extracts (9.6 versus 1.9 and 2.5 %), and low moisture content (51.7 versus 69.3 and 71.5 %), protein (11.2 versus 16.6 and 17.2 %), ash (0.9 versus 1.1 and 1.3 %) and vitamin C (67.5 versus 87.9 and 97.6 %). The fatty acid composition of muscle lipids of farmed fish was generally comparable to that of lake and pond fish - the main groups of fatty acids were at a similar level: polyunsaturated fatty acids in the range of 37.0-40.6 % of the total fatty acids, saturated fatty acids - 25.5-29.6 %, monounsaturated fatty acids - 28.0 and 23.2 % in farmed and lake fish, and 17.5 % in pond fish. The content of arachidonic acid 20: 4n-6 in farmed fish was extremely low (1.0 versus 8.0 and 11.5 % of the total fatty acids). Liver lipids of farmed fish contained a large amount of oleic acid 18:1n-9 (30.3 versus 16.2 and 15.0 % of the total fatty acids in lake and pond fish) and n-6 polyunsaturated fatty acids (17.5 versus 8.4 and 7.1 %), in particular linoleic acid 18:2n-6 (7.0 versus 1.9 and 0.2 %). The blood of farmed fish, compared to pond fish, differed in a lower content of hemoglobin (64.8 versus 74.8 g/l), an increased content of immature lymphocytes (11.6 versus 6.1 %) and immature erythrocytes (2.2 versus 1.1 %). The gonads of farmed fish were at stage III of maturity with an average oocyte diameter of 478.9 µm; lake fish had two stages of oocyte maturity - previtellogenic oocytes of protoplasmic growth, 62.7 µm in size, and significantly larger vitellogenic oocytes of trophoplasmic growth - 227.6 µm. In pond pikeperch, gonads corresponded to stage II of maturity and oocytes were 58.3 µm in size. Certain differences in pikeperch from lakes, ponds and farm conditions are associated with different conditions of fish keeping and feeding.

An analysis of the community of rodents and insectivores in five biotopes of the southern forest-steppe of the Northern Kulunda was carried out. High biodiversity is typical for the coastal strip with dense herbage near the lake, and low biodiversity is typical for the feather grass-forb steppe. At the beginning of the 21st century, there was a change in dominance in the community of small mammals, and the species richness increased. Of the five shrew species, only the common, tundra and lesser shrews inhabit all biotopes. Their total share in each biotope ranged from 16 % to 38 %. Among the 11 rodent species, the narrow-skulled vole is the dominant species. Its cumulative share in the community of small mammals was 38,3 %. This species is characterized by a peculiar cycle of abundance. The reduction of steppe habitats has led to a decrease in the number of steppe lemming and a change in its population cycle. The share of other rodent species in the community of small mammals is low.

The difficult natural conditions of the Purovsky District of the Yamal-Nenets Autonomous Area determine the insufficient floristic knowledge of this territory. The high degree of anthropogenic transformation of the vegetation of the area makes it necessary to identify habitats of rare plant species in order to preserve and restore their numbers. The expedition studies carried out by the authors in 2019 allowed us to obtain new information about the distribution of 6 rare plant species. Three species (Corallorhiza trifida Chatel., Botrychium multifidum (S.G. Gmelin) Rupr., Neottia cordata (L.) Rich.) have small locations within the Yamal-Nenets Autonomous Area and were first found in the Purovsky district. For three species (Goodyera repens (L.) R. Br., Dactylorhiza fuchsii (Druce) Soó, Lycopodiella inundata (L.) Holub), new locations have been identified that are significantly removed from previously known ones. Three species are included in the main list of the Red Book of the Yamal-Nenets Autonomous Area (Corallorhiza trifida, Dactylorhiza fuchsii, Lycopodiella inundata), two - in the Appendix to it (Botrychium multifidum, Goodyera repens). A rare species of the Orchidaceae family, Neottia cordata, was previously known from two localities in the mountainous part of the Yamal-Nenets Autonomous Area; two new localities were identified in the Purovsky district. In one of them, a large population of Neottia cordata was noted, which is of particular importance for the conservation of the species, because Currently, the number of localities in the Russian part of Neottia cordata is decreasing. The species needs protection and should be included in the Red Book of the region. The presented data complements information on the distribution of rare plant species and is necessary for further monitoring.

Based on studies of the biota of agaricoid basidiomycetes in Southern Siberia, information is provided on the morphology, distribution and ecological association of 3 new agaricomycete species for the mycobiota of Siberia: Hemimycena tortuosa (P.D. Orton) Redhead, Entoloma formosum (Fr.) Noordel., E. sublaevisporum Vila, Noordel. et O.V. Morozova, found in steppe and forest communities of Western and Eastern Siberia. The species Hemimycena tortuosa is also new to Russia.The specimens of this species are kept in the Herbarium of M.G. Popov of the Central Siberian Botanical Garden SB RAS (NSK).

Valentina Nesterovna Vasilyeva is one of the leading breeders and introducers of sunflower seeds in Siberia. All her scientific activities were connected with the Botanical garden in Novosibirsk. A number of varieties of apple, currant, gooseberry, in the breeding of which she took part, are zoned for Northern Kazakhstan, Western Siberia and other regions of Russia.