№ 1 (2025)

A modeling of the Black Sea circulation for 2016 was carried out with different sets of atmospheric forcing data to determine the optimal atmospheric forcing for retrospective analysis of hydrophysical fields. An eddy-resolving z-model of Marine Hydrophysical Institute with a resolution of 1.6 km was used for the calculations. Differences in the circulation structure for the two experiments were revealed. It was shown that in the SKIRON experiment compared to ERA5, the cyclonic circulation of the Black Sea was weakened, the isopycnic surfaces were aligned, and the cold intermediate layer was not determined by the 8°C isotherm due to the underestimation of the solar radiation flux and weakening of the wind influence. A comparison of the model thermohaline characteristics calculated using ERA5 and SKIRON atmospheric forcings and measurement data of temperature and salinity obtained by ARGO profiling floats and onboard equipment in 87, 89, 91 cruises of R/V Professor Vodyanitsky was carried out. According to the validation results, it was obtained that in the upper 300-meter layer, for all measurement stations the mean RMSE of temperature and salinity in the ERA5 experiment were 28 and 17% lower, respectively, than the RMSE calculated from the SKIRON data.

The paper aims to find the correlation relationship between the land–water area ratio for a fixed area of the Danube Delta and the total river discharge using Landsat series satellite products and SMHI Hypeweb hydrological model. The study period covered 1984–2010. We used a total of 132 satellite images in one band in the near-infrared spectral range with a spatial resolution of 30 m. Two study areas were selected: the delta area with channel and land (44.9–45.4° N, 29.55–29.60° E) and the control area of the mouth seashore (44.9–45.4° N and 29.80–29.85° E). For each of them a histogram was plotted which characterised the reflected light in relative units and their corresponding numbers of pixels. The signal from the first area was found to be in the range of 7000–26,000 r.u., whereas from the second one it was 7000–8000 r.u. This distinction allowed us to separate the delta areas occupied by river water from those of land. For this purpose, we calculated the ratio between the number of pixels corresponding to a value of 7000–8000 r.u. to all pixels in the area. Then we found the correlation between the river discharge from the SMHI Hypeweb hydrological model and the proportion of pixels corresponding to areas occupied by water. The regression y = 7.78∙10^–4∙x ^0.09 – 5.98∙10^–4 was obtained. The analysis of seasonal variability showed that in the studied delta area, the share of pixels related to water-occupied areas > 0.5 corresponds to the months from March to May, and the minimum values < 0.3 correspond to July–September. All this is consistent with the period of intensity of precipitation and snowmelt in the Danube River basin area. The data from this work may be useful to researchers assessing the impact of this river discharge on the hydrological regime and condition of the Black Sea.

The paper analyzes the effectiveness of a pile breakwater structure Grebenka for coastal protection purposes. From 03.10.2020 to 30.04.2023, full-scale testing of the structure was conducted on the northern shore of the Kaliningrad Oblast near the city of Zelenogradsk between the eroded and accumulative shore segments. Four breakwater modules were installed in a single line in the groin pocket at a depth of about 2 m offshore of the groin end but did not completely overlap the pocket. One module was installed in the immediate vicinity of the shoreline. The experiment covered several seasons of severe storms, which allowed us to compare the shoreline dynamics at the breakwater installation site and in the neighbouring areas. We carried out regular measurements of the beach width, aerial survey, repeated depth measurement at the installation site and assessed the underwater slope dynamics. We also determined the thickness of the sand cover layer at the structure installation site and placed tilting flow velocity sensors on the breakwater. It was found that the beach width at the breakwater installation site and in adjacent areas was changing synchronously. The absence of an obvious accumulative effect behind the installed breakwater was, first, due to the displacement of the breakwater modules and their partial immersion in the sand and, second, due to the limited line length of the offshore modules in proportion to their distance from the shoreline. A temporary positive effect was achieved only for a solitary module as periodic beach progradation to the root of an old groin adjacent thereto from the east. The results of the full-scale test will be used to further improve the breakwater design.

The paper aims to analyse the results of long-term studies of dissolved and suspended organic matter content in the waters of the Northern Caspian and Middle Caspian in the Russian sector of the Caspian Sea. The paper analyses the main sources of input of organic matter, itsseasonal and inter-annual variability, features of its spatial distribution and causes (allochthonous organic matter flow, production and destruction, water temperature, sea level changes, etc.) determining the spatial and temporal dynamics of organic matter content. Thepaper is written on the results of production environmental monitoring conducted atthelicensed areas of LLC LUKOIL-Nizhnevolzhskneft in 2017–2021. The organic matter amount was estimated by organic carbon. The dissolved organic carbon concentration was found to vary from 0.10 to 9.30 mg/dm³ in the surface water layer and from 0.10 to 9.60mg/dm³ in the bottom layer. The maximum enrichment of waters with dissolved organic matter was noted in the northern part of the water area. The concentration of suspended organic carbon in the surface water layer varied within 0.10–23.40 mg/dm³, whereas inthebottom water layer it ranged within 0.05–19.40 mg/dm³. The spatial distribution of suspended organic matter was characterized by seasonal shifts of the area with maximum concentrations northwards. The main factors affecting the organic matter content in water were water temperature, suspended matter concentration in water and hydrogen ion concentration. The level of dissolved and suspended organic matter has not changed in the last 20years of studies. The dependence of dissolved and suspended organic matter concentrations on environment pH indicates the natural origin of the organic matter in the waters of the monitored sea area.

The paper estimates the dynamics of the settlement of mytilasters in the coastal water area with different degrees of petroleum pollution using the example of Sevastopol Bay (high level of anthropogenic load) and Laspi Bay (conditionally clean water area). To assess the marine environment quality at the sites of mytilaster fouling in the mentioned bays, data on the petroleum hydrocarbons content in the water was analysed (2012, 2015, 2018). The study material was samples of Mytilaster lineatus mollusks and bottom sediments taken in Sevastopol Bay from 2012 to 2018 at depths from 7 to 17 m during three sanitary and biological surveys. The abundance of mytilasters on various natural and artificial substrates of Sevastopol Bay in 2012, 2015 and 2018 under conditions of chronic oil pollution was analysed. It was revealed that the abundance of mytilasters on solid substrates was primarily influenced not by pollution of the marine environment but by water temperature and surf-wave phenomena. The values of the index of functional abundance show that under chronic petroleum pollution, mytilasters, inhabiting artificial substrates of Sevastopol Bay, make a more significant contribution to transformation of matter and energy. At the same time, the energy significance of the studied mollusks in the soils of Sevastopol Bay is considerably lower than that in the conditionally clean water area (Laspi Bay). An analysis of average abundance and biomass of mollusks for 2012, 2015 and 2018 showed that the number of mytilasters in the marine soils of Sevastopol Bay increased. It was established that the quality of life of the community was influenced by the physical and chemical parameters of bottom sediments, which either accelerate or slow down the oxidation processes, thereby changing the oxygen level in the bottom sediments. According to the correlation analysis results, there is a direct relationship between the abundance, biomass of mollusks and concentrations of chloroform-extractable substances, petroleum hydrocarbons and redox potential. It was revealed that in the soils of Laspi Bay, the quantitative indicators of mytilasters were four times higher than in Sevastopol Bay.