In 2023, comprehensive studies of shallow-water methane gas emissions were conducted during expeditionary work in the coastal area of Laspi Bay (southwestern coast of Crimea). The research included determining the component and isotopic composition of bubble gas, measuring methane concentration in the gas emission area, estimating bubble flux rates, and measuring hydrophysical parameters above the seep site. The obtained results of the carbon isotopic composition of methane and ethane in the studied samples corresponded to (δ13Cmean = –36.0 ± 0.8‰, δ13Cmean = –37.5 ± 0.2‰, respectively) and indicate the presence of thermocatalytic methane migration along fault systems. It was found that the methane seeps of the Crimean coast are relatively low-flow, with a specific flux ranging from 5 to 10 m3 year-1 from an individual seep. The presented temporal dynamics of dissolved СН4 concentration above the seep and changes in the isotopic ratio of δ13C-СН4 in bubble gas indicate the constancy of the process over time and the absence of connection with external hydrological changes in the water area. The obtained ratios of the carbon isotopic composition of methane and ethane demonstrate that the gas mixture was most likely generated from source organic matter of marine origin, and one of the main sources of hydrocarbon fluids is the Upper Eocene and Oligocene deposits in the Western Black Sea basin.

The spatial and temporal changes of the concentration and distribution of an organochlorine pesticide p,p'-dichlorodiphenyltrichloroethane (DDT) and its metabolites and caesium-137 in bottom sediments of the longest Crimean river Salgir were studied. The spatial distribution of ∑DDT and caesium-137 concentrations has uneven focal nature. Maximal concentration of ∑DDT, exceeding the estimated permissible levels in bottom sediments by more than 10 times was detected in the middle reaches of the river in areas near the villages of Krasnaya Zorka and Pyatikhatka (270 and 256 ng/g dry mass, respectively). In these areas, the share of DDT in its total concentration with metabolites was >40

From 2010 to 2022, the summed concentrations of six indicator polychlorinated biphenyls (∑6PCB) and DDT with metabolites DDE and DDD (∑DDT) in the surface layer of the coastal Black Sea areas of Crimea varied from 0.05 to 34.9 and from 0.01 to 7.44 ng/L, respectively. The maximum concentrations of both groups of compounds were found during spring seasons. With the total variability in the ∑DDT content in water being significant, their average concentration tended to decrease in the study period. For PCBs, this trend was not detected. The ∑DDT concentration in mesozooplankton in the studied water areas in 2016, 2017, and 2019 reached 34.3; ∑6PCB, 475 ng/g dry weight. A positive correlation between the ∑DDT concentration in mesozooplankton and water samples (R 2 = 0.77) and the lack of such correlation for ∑PCB (R 2 = 0.03) was revealed. It was determined that the accumulation of ∑PCB and ∑DDT in mesozooplankton was directly correlated with the total lipid content in organisms. In the surface layer of sediments in open areas of the Black Sea water area of Crimea, the content of PCB congeners 101, 138, 153, and 180 was the same in 2016 and 2019, which indicates stabilization of the technogenic load on the studied water areas.

We report on methane (CH4) concentration measurements in the northern Black Sea area conducted during 6 cruises with R/V Professor Vodyanitsky from 2017 to 2019. Our work is a multi-season study at a uniform station grid covering an area of 88 x 10(3) km(2) and including three latitudinal transects that comprises both surface and vertical profile water-column measurements. The main goal of the work was to assess the seasonal patterns of vertical CH4 structure in the aerobic water column (upper 100 m) and its emission to the atmosphere. In surface waters, the mean dissolved CH4 concentration ranged from 2.6 nmol L-1 detected in November 2018 to 11.5 nmol L-1 measured in June-July 2018, respectively. Calculated CH4 seawater-air fluxes and saturations were mostly positive (i.e. net flux to atmosphere), and winter fluxes (2.6 mu mol m(-2) d(-1)) were higher than summer fluxes (1.6 mu mol m(-2) d(-1)) due to the higher wind speed. The integral CH4 flux from the whole study area (88 x 10(3) km(2)) ranged from 84 to 235 kM day(-1). It was shown that, on average, the methane concentration in the upper layer for deep-water stations where the seabed is located at depths >160 m (sigma t >16.2) was lower compared to stations at shallow water depths (28-140 m, sigma t <16.2). The most distinct difference was obtained for the summer season (June-July 2018) and a less significant difference - for spring (April-May 2019) and winter season (November-December 2018). During these seasons the water column was also considerably less saturated in CH4 compared to the entire monitoring period. We observed subsurface maxima, which were generally located at the base of the thermocline and exceeded 100 nmol L-1 at some stations. Exceptions were observed in October 2019 (cruise 110), when vertical CH4 distributions were characterized by two-peaks at similar to 20 and similar to 50 m depth. The strong influence of the thermohaline structure on the water column CH4 distribution has also been shown in studies of daily dynamics of CH4 vertical profiles in the shallow water region. Despite the high variability of CH4 concentrations, significant similarities in vertical distributions of CH4 and chlorophyll-a for which sub-surface maxima coincided at some stations, are shown. Extremely high concentrations of CH4 (up to 351 nmol L-1) in the near-bottom water layer were revealed during all seasons at the station near the Dnieper paleo-channel at the northwestern edge of the study area. This enrichment is assumed to be caused by methane emissions from gas seeps densely located in this region.

Methane are widely used in industry as an emerge source may be released significantly higher aquatic ecosystems due to gas seepages. In this study, short-term (90 min) methane effects on bivalve hemocytes were investigated using flow cytometry. Hemocyte parameters including hemolymph cellular composition, phagocytosis activity, mitochondrial membrane potential and reactive oxygen species (ROS) content were evaluated in the mussel Mytilus galloprovincialis (Lamarck, 1819) exposed to hypoxia (control group), pure methane and industrial methane (industrial hydrocarbon mixture). Comparison of biomarkers showed that the mussel was more sensitive to methane than to low oxygen concentration, supporting the effects of methane on the mussel's immune system. After exposure to pure and industrial methane, the number of granulocytes decreased dramatically and the levels of reactive oxygen species, mitochondrial membrane potential and phagocytosis capacity increased significantly. It was shown that the methane type-dependent effect was pronounced, with industrial methane leading to more pronounced changes.

— Gas seep and fluid flows from the seabed are an environment-forming factor of the aquatic environment, mainly due to their influence on the dissolved gases in the water, including dissolved oxygen. During the summer seasons from 2019 to 2021 in the area of shallow water gas emission site off the southern coast of the Heracles Peninsula, series of vertical probing profiles were carried out to determine hydrological parameters of the water: dissolved oxygen concentration (O 2 ), temperature ( T ), salinity ( S ), and flow velocity ( U ). The study area is an underwater ledge with faults in the form of three canyons composed of dense limestones, two of which contained bubble gas emissions. Significant variability in O 2 was identified in canyons where gas emissions are observed: from 1 to 80% saturation in the bottom layer, in contrast to normoxia at the background sites. Hypoxia was observed in the bottom layer above the emission sites in the absence of turbulence at temperature stratification. The values S decreased with depth, and the maximum difference reached 0.4‰. The bubble gas was dominated by methane (68.5–75.5%), and the carbon isotope composition of the bubble methane gas varied from –67.9 to –59.8‰ VPDB in 2019 and 2020, respectively. This generally indicates that the CH 4 is of predominantly microbial genesis, was formed under different conditions, and matured in various periods of research during the monitoring period. Bacterial mats (mostly sulfur-oxidizing bacteria) were found in the areas of gas emissions.

Data on the abundance of petrogenic and trace elements (including rare earth elements) in the Quaternary deposits of Sevastopol Bay at the pre-technogenic stage of its development were obtained. Anomalies in the enrichment with Ag, Au, Hg, Pb and elevated levels of Cu, Zn, Cd, Sn, Sb in some layers were discovered. These features are apparently due to sulfide mineralization in the denudation area and the emergence of specific geochemical barriers (hydrodynamic and, possibly, saline ones) in the periods of changes in the paleogeographic environment. The ratios of the contents of elements sensitive to the change in the weathering type made it possible to establish the climate characteristics in the source area. During the accumulation of the liman deposits, relative warming and humidization took place, with the boundary strata of this period evidencing drier and colder conditions at the very beginning and completion of the deposit formation. The marine stage begins with warming (the lack of samples in the lower and middle parts does not allow us to trace further the prevailing conditions), but cooling and aridization are observed later on. These constructions fit into the general regional picture of climate change in the southwestern Crimea in the interval of 9.5–3.0thousand years ago.

Data on the abundance of petrogenic and trace elements (including rare earth elements) in the Quaternary deposits of Sevastopol Bay at the pre-technogenic stage of its development have been obtained. Anomalies in the enrichment with Ag, Au, Hg, and Pb and elevated levels of the Cu, Zn, Cd, Sn, and Sb concentrations have been recorded in some layers. These features are apparently determined by sulfide mineralization in the source area and the appearance of specific geochemical barriers (hydrodynamic and, possibly, saline ones) during changes in the paleogeographic environment. The ratios of the concentrations of elements sensitive to changes in the weathering type have made it possible to establish the climate characteristics in the source area. The accumulation of estuary deposits was accompanied by relative warming and humidification, with the boundary strata of this period evidencing drier and colder conditions at the very beginning and at the end of the formation of the deposit. The marine stage begins with warming (the absence of samples in the lower and middle parts does not allow us to trace further prevailing conditions); however, cooling and aridization are then observed in the Dzemetinian period. Relative salinity peaks correspond to several supposed periods of aridization. These constructions fit into the general regional picture of climate change in southwestern Crimea and the Black Sea region between 9500 and 3000 years ago.

Purpose. The purpose of the study is to assess the diurnal dynamics of CH4 vertical distribution in the aerobic zone of the Black Sea at the stations of different depths joint with surveying the sound scattering layers (SSL).Methods and Results. The surveys were performed in the 113th cruise of the R/V Professor Vodyanitsky (June, 2020) in the upper 100-m layer at the deep-water station (1570 m) in the northeastern Black Sea, and at the shallow-water station (39 m) in the Yalta Bay. The differences in vertical distribution of the CH4 concentration in the seawater in these areas were found. Diurnal range of the CH4 concentrations in the surface water layer (0-1 m) was 0.8-16 nmol/l and 0.2-7 nmol/l for the shallow and deep-water areas, respectively. Shown was the fluxes' high variability at the water - atmosphere boundary in course of a day, namely, from the atmospheric CH4 inflow to the seawater up to the CH4 emission (up to 3 mu mol/m(2)day) to the atmosphere.Conclusions. The maximum CH4 fluxes to the atmosphere recorded at both stations were observed at night. It was shown that the atmospheric CH4 emission to seawater was not a significant factor in the CH4 redistribution in a water column since the calculated values of the atmosphere - seawater specific daily CH4 flux constituted the fractions of a percent of its store in the water column. Diurnal dynamics of the vertical CH4 distribution and SSL in the aerobic layer of the deep-water station was revealed to be of a similar pattern. Against high variability of the data for the individual time ranges, obtained were significant determination coefficients between the CH4 concentration and the sound-scattering coefficient of layer ml' as a characteristic of the biomass amount.

From 2019 to 2021, integrated studies of new shallow-water methane bubble gas seeps were carried out in the coastal zone near Cape Fiolent (Southwest Coast of Crimea). The studies included determination of the hydrocarbon and isotope composition of bubble gas, measurement of the methane and nutrient concentration in the water in the areas of gas seeps, estimation of the value of bubble flows, and measurement of the hydrophysical parameters over the seep sites compared to background areas. A seasonal type of Cape Fiolent methane seeps was noted, and the durations of its active gas emission phases differed in different years. The increased pore water silica concentration at the seep sites and their localization in the vicinity of freshwater slope springs may indicate its association with submarine freshwater discharge in the area. However, no significant desalination of either pore water or the bottom water layer above the seeps was recorded. Dissolved methane concentrations in pore water at seep sites were two orders of magnitude higher compared to the background areas, reaching 448 μmol/L. High values were also obtained for surface water directly above the bubble gas emission points (maximum 353 nmol/L). Multihour monitoring of the hydrophysical parameters above the active seeps showed a decrease in dissolved oxygen compared to the background sites. The maximum difference in O2 concentrations was 3 mg/L. The carbon isotope composition of bubble gas methane δ13C-CH4 (–62.84 to –38.27‰) and carbon dioxide δ13C-CO2 (–16.83 to –10.17‰) corresponded to a mixture of isotopically heavy gas and near-surface isotopically light gas of microbial origin. The question remains open: what are the reasons for the change in the summer active and cold season passive gas emission phases?

This work is devoted to studies of the shallow methane seepages temporal variability in the coastal area of Laspi Bay and high-frequency monitoring of the hydrological parameters daily dynamics in this area. The paper presents results obtained during the summer months of 2016, 2018-2021, and early February 2023. Using the passive acoustic method, it is shown that the intensity and periodicity of bubble gas emission by individual point sources can vary during the day and from season to season. It was obtained that a decreased content of dissolved oxygen and its saturation is observed above the active site of the seepages as compared to the distant (background) site. Moments of sharp decrease in oxygen content not accompanied by changes in temperature and other hydrological parameters were noted.

Concentrations of organochlorine compounds (OCs) were determined, and comparative analysis of OCs in the bottom sediments of the Chernaya river, small lakes of the Baydar valley, the Sevastopol Bay and the Chernore-chensky reservoir, sampled in 2008 and 2019-2020, was carried out. A noticeable difference in the levels of OCs pollution in the river, lakes and the bay was detected. This concerns mainly such OCs as polychlorinated biphenyls (PCB), the content of which in sediments of the studied areas varied within a wide range - from 0.5 in lakes to 900 ng/g dry weight in the Sevastopol bay. Increased anthropogenic pressure on the river water area in the region of Baydar valley and in the estuary area has led to the formation of zones with the local maxima of the concentrations of PCB and organochlorine pesticides (1,1,1-trichloro-2,2-bis(chlorophenylethane), DDT) in the bottom sediments of the Chernaya river. In the Baydar valley, the sediments in lakes were on average less contaminated than river sediments, which is due to the isolation of lake ecosystems; they may be classified as non-polluted and weakly polluted. The maximal OCs concentrations were detected in the Sevastopol Bay. The ratio of DDT metabolites in the composition of organochlorine pesticides depended on redox conditions in bottom sediments: under anaerobic conditions of the Sevastopol Bay, DDT was transformed into DDD (1,1-dichloro-2,2-bis(4-chlorophenyl)ethane), under aerobic conditions in the river sediment - into DDE (1,1-dichloro-2,2-bis-(4-chlorophenyl)ethylene). Reconstruction of sedimentation geochronology using radiotracer methods shows that the variability of OCs content at different depths of fresh-water sediments depended on the temporally varying amounts of OCs income into the water areas but not on the natural conditions of sediment formation. According to estimates, at present, the runoff from the Chernaya river contributes not more than 14 % Sigma DDT and 4 % Sigma 6PCB into the bottom sediments of the Sevastopol Bay.

The vertical distribution of temperature ( T ), salinity ( S ), dissolved oxygen (O2) concentration, flow velocity ( U ) in the underwater canyon over the gas seepage site in the Golubaya Bay (the Black Sea) is studied. A significant decrease in the O2 concentration in the bottom water layer over the seep site as compared to the background site is shown, with a minimum of 0.2 mg/l, which was kept during the entire measurement period. The minima at the bottom were also revealed in the distribution of salinity in the first dataset; in the second dataset, desalination lenses were registered at a depth of 4, 10, and 8 m for three consecutive soundings. Such distribution potentially indicates a pulsed freshwater discharge, during which the desalination lenses gradually rise to the surface. The bottom current in the canyon was on average two times weaker than at the background station, where its velocity varied within 0.04-0.09 m/s. The described features of the distribution of hydrological parameters are associated with the gas bubble seepage and geomorphology of the study area.

The results of investigation of oscillations of an airfoil on an elastic hinge that performs transverse sinusoidal oscillations in the free stream of a viscous incompressible fluid are given. The motion of the hinge is specified and the angular oscillations of the airfoil occur under the action of hydrodynamic and elastic forces. The problem of fluid-structure interaction is solved in the complete coupled formulation. Fluid is described by the Navier–Stokes equations whose numerical solution is constructed using the meshless method of viscous vortex domains. Simulation of the related motion of the continuous medium and the rigid body is reached by solving the united linear system of equations in which the unknowns are the vorticity fluxes from the body surface and the velocity of rotational motion of the body. As a result, all unknown quantities are calculated simultaneously in each time step omitting the traditional procedure of splitting the step into the hydrodynamic and dynamic parts with subsequent iterations. The mechanisms underlying the thrust in such motion of airfoil and the role of the added mass force in this process are explained.

tri bu tion of Hy dro log i cal Pa ram e ters over the Meth ane Seep Site in the Golubaya Bay (the Black Sea): A Con nec tion with Sub ma rine Fresh wa ter Dis charge T. V. Malakhova*, I. N. Ivanova, A. A. Budnikov, A. I. Murashova, and L. V. Malakhova Kovalevsky In sti tute of Bi ol ogy of the South ern Seas, Rus sian Acad emy of Sci ences, pr. Nakhimova 2, Sevastopol, 299011 Rus sia Lomonosov Mos cow State Uni ver sity, GSP-1, Leninskie Gory, Mos cow, 119991 Rus sia

Fluid methane discharge fluxes from bottom sediments were measured (using the trapping method) in four areas of the Chernaya River estuarine zone. The sampling stations were characterized by different hydrological–hydrochemical conditions: the water samples differed in salinity, content of biogenic elements of nitrogen and phosphorus complexes ( $${\text{NO}}_{2}^{ - }$$ from 12.2 to 29 μg L–1; $${\text{NO}}_{3}^{ - }$$ from 294 to 869 μg L–1; $${\text{NH}}_{4}^{ + }$$ from 57.9 to 130 μg L–1; and $${{{\text{H}}}_{{\text{2}}}}{\text{PO}}_{4}^{ - }$$ from 28.2 to 127.8 μg L–1), and geochemical characteristics of the bottom sediments. The mineral forms of nitrogen and phosphorus, porosity, and sediment moisture decreased against the salinity gradient, i.e., from the river source to its mouth. A similar trend was determined for methane concentration in the bottom sediments and water at the surveyed stations. Methane concentration in bottom sediments at brackish-water Stations 1 and 2 was two orders of magnitude lower than at freshwater Stations 3 and 4, where the concentration reached 1.1 mmol dm–3. Methane content in the pore water of the bottom sediments did not exceed the calculated solubility values, which ranged from 1.53 to 1.68 mmol L–1. The range of average methane concentrations in water at the studied stations varied from 285 to 813 nmol L–1. The variations in methane concentrations in the water show an oscillatory pattern, which is presumably related to wave processes in the estuary. The variations in methane concentration in the fluid traps over time define a linear trend, which allowed us to calculate the flow of dissolved methane from the bottom sediments. For stations 3 and 4 upstream of the Chernaya River, the flow was 4 and 293 mmol m–2 day–1, respectively. Significantly lower flows were calculated for brackish-water stations 1 and 2 (0.3 and 0.4 mmol m–2 day–1), which is likely explained the life activity of methanotrophic bacteria, where sulfate-dependent oxidation of methane is carried out in the upper layer of the bottom sediments in the presence of the sulfate ion.

The effect different types of bottom soil have on the acoustic signal produced by air bubbles passing through the soil into water is considered. The gas flux is calculated using data from recording of the acoustic signal produced by active bubbling methane seepages in Laspi Bay, allowing for the error introduced by the soil. The inconsistency in the intensity of the methane fluxes is demonstrated.

Представлены данные о содержании хлорорганических пестицидов (ХОП) и полихлорированных бифенилов (ПХБ) в подкожном жировом слое черноморских дельфинов - афалин, белобочек и морских свиней (азовок), выброшенных на крымское побережье в 2017 г. Во всех исследованных пробах обнаружены α-, β- и γ-ГХЦГ в интервале концентраций от 0,003 до 0,264 (∑ГХЦГ от 0,036 до 0,319); гексахлорбензол – от 0,12 до 8,14; п,п’-ДДТ и его метаболиты п,п’-ДДЭ и п,п’-ДДД – от 0,08 до 146,95 (∑ДДТ от 1,27 до 163,18); а также шесть конгенеров полихлорбифенилов (по IUPAC: 28, 52, 101, 138, 153 и 180) – от 0,004 до 11,28 (∑ПХБ6 от 0,42 до 27,04) мкг·г–1 липидной массы. Доля п,п’-ДДЭ составляла от 44 до 90% суммы ХОП и достигала 146,95 мкг·г–1 липидной массы. Максимальная концентрация ХОП и ПХБ зафиксирована в пробах подкожного жира белобочек.

The reverse vortex street differs from the ordinary Karman vortex street in the direction of the rotation of the vortices. Such a street is formed behind the oscillating airfoils in the flow. It is of interest in connection with studies of the aerodynamics of flapping wings. It is known that the vortex wake behind a symmetric airfoil performing symmetric oscillations in a certain range of parameters becomes asymmetric, which leads to the appearance of a nonzero average lift. Reasons of the symmetry violation are associated with the instability of the reverse vortex street, but the mechanism of this instability is currently not well understood. In this work, the analysis of the stability of the reverse vortex street is carried out on the basis of the theory developed by Karman for infinite rows of point vortices. In contrast to the Karman model, in this work, semi-infinite rows with periodically arising new vortices at their ends are considered. This is the first time this model has been used. It is shown that the periodic appearance of new vortices radically affects the characteristics of the street stability. It is found that the violation of the symmetry of the reverse vortex street is associated with its instability to bending perturbations, while the ordinary Karman vortex street behind the body is unstable to varicose perturbations. Regions of instability are determined.