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The article presents the results of comprehensive studies of the hydrological and chemical structure of the Middle and Northern Caspian Sea carried out aboard R/V Issledovatel Kaspiya in September 2022. It is shown, despite the continuing decrease in sea level, that there is no aeration of deep layers and a hydrogen sulfide layer persists with a tendency towards an increasing hydrogen sulfide concentration in the bottom layer. There is an enlargement in the oxygen minimum zone. The changes of the Caspian Sea ecosystem have led to weakening of nutrient transfer from the photic layer into the bottom layers and, as a consequence, to a decrease in the silicon concentration in the bottom layer. The results will make it possible to evaluate trends of ongoing changes. [ABSTRACT FROM AUTHOR]

The article presents the results of applying the a probing complex for recording particles with a study of discovery of an assemblage of euphausiids in the bottom water layer in the Stepovogo Bay in the Kara Sea during cruise 85 of the R/V Akademik Mstislav Keldysh in September 2021. [ABSTRACT FROM AUTHOR]

Brief results of oceanological studies in the south-eastern Baltic Sea and Gulf of Finland on cruise 54 of the R/V Akademik Sergey Vavilov (2022) are presented. Hydrological, hydro- and geochemical, hydrobiological, geoecological, geological, and geophysical studies were carried out. New data on the state and dynamics of the Baltic Sea natural complexes under conditions of increasing anthropogenic pressure and climate change were obtained. [ABSTRACT FROM AUTHOR]

On cruise 61 of the R/V Akademik Ioffe (June 28–July 12, 2022), a comprehensive oceanographic survey was carried out in the Russian sectors of the Southeastern Baltic Sea and Gulf of Finland. In conditions of long-term absence of Major inflows of North Sea water, hypoxia and anoxia continue to develop in deep waters. In the eastern part of the Gdansk Deep, a contourite drift was identified for the first time, formed during the Littorina phase of the Baltic Sea. Together with Kant Baltic Federal University, an integrated study was carried out on the offshore site of the Carbon Supersite 'Rossyanka' and the V International Summer School "Coastal Zone of the Sea: Research, Management, and Prospects" was held. [ABSTRACT FROM AUTHOR]

Brief results of comprehensive studies of the southeastern Baltic Sea on cruises 47–49 of the R/V Akademik Boris Petrov (2021–2022) are presented. Research methods included geophysics, geology, paleogeography, hydrology, hydro- and geochemistry, hydrobiology, and geoecology. New data on paleolandscapes and parameters of long-term monitoring of spatiotemporal changes in the abiotic and biotic components of the Baltic Sea ecosystem were obtained. [ABSTRACT FROM AUTHOR]

The paper presents brief results of comprehensive studies of waters of the Tatar Strait and Sea of Japan, obtained on cruise 79 of the R/V Professor Gagarinsky in May–June 2022. The distribution of geophysical fields was obtained, the block's divisibility of the bottom of the water area was confirmed, and new data was obtained on the distribution of gases in the sedimentary sequence, bottom, and surface water. The electrokinetic parameters of microorganisms for evaluating their relationship with methane concentration was obtained, and micropalentological analysis of sedimentary deposits was performed. [ABSTRACT FROM AUTHOR]

During the 78th cruise of R/V Professor Gagarinsky, geophysical studies of the shelf, continental slope, and abyssal basin of the northwestern Japan Sea were carried out. New data are obtained on the structure of the seabed, the structure of the sedimentary cover, and the features of the magnetic field. [ABSTRACT FROM AUTHOR]

On cruise 93 of the R/V Akademik M.A. Lavrentyev (2021), we studied benthic communities in the Gamov Canyon (Sea of Japan), off the eastern coast of Kamchatka, and methane seep communities of the Koryak slope (Bering Sea); in addition, data were obtained on the sea-air mercury flux. The studies confirm the potential of the Gamov Canyon as a model site for long-term monitoring. We document significant changes in the structure and composition of the fauna compared to 2018 in the background and methane seep communities of the Koryak slope. [ABSTRACT FROM AUTHOR]

The 51st cruise of the PV Akademik Sergey Vavilov (June 30–July 14, 2021) included the study of redox conditions in the Baltic Sea deeps. Water temperature in the upper quasi-uniform layer significantly exceeded average climatic values for July, especially in the Gulf of Finland (by 7–7.5°С) due to abnormally hot weather. A setup of cyanobacterial aggregates from the subsurface layer to the surface was observed, it occurred earlier than normal. In cooperation with the Immanuel Kant Baltic Federal University an integrated survey was carried out at the Kaliningrad carbon polygon and the IV International Summer School "Coastal Sea Zone: Research, Management and Perspectives" was held. [ABSTRACT FROM AUTHOR]

The paper presents brief results of integrated studies of the northern part of the Sea of Okhotsk close to of the Kuril arc, obtained on cruise 92 of the R/V Akademik M.A. Lavrentiev in April–May 2021. The relief was refined and the distribution of geophysical and gas-geochemical fields was obtained. Volcanic edifices hidden in the sedimentary layer were discovered. A large array of data was obtained on the distribution of temperature and salinity of surface waters, as well as the concentrations of methane, carbon dioxide, and atomic mercury in the near-water atmosphere along the route of the vessel. [ABSTRACT FROM AUTHOR]

During the 56th cruise of the P/V Akademik Ioffe (August 2020) in the Baltic Sea, hypoxia was registered at a water depth of 80 m, hydrogen sulfide in the East Gotland Basin was detectable at 90 m above bottom, which is 25 m higher than in August 2019. In area of the "benthic desert" local habitats of species of bivalve mollusc Astarte borealis were found. Based on hydrophysical sounding data, a regional scheme of bottom currents induced by Major Baltic inflow events has been developed. High-resolution sub-bottom profiling and side-scan sonar in the East Gotland Basin allowed defining the thickness of marine sediments more precisely and revealing their asymmetry, as well as developing a digital terrain model. A detailed picture of the mosaic distribution of acoustic anomalies associated with the seeps of hydrocarbon gases to the bottom surface was obtained. New areas of distribution of iceberg plough marks, including buried ones, have been revealed. A previously unknown contourite drift was found in the northeastern part of the Slupsk Furrow. [ABSTRACT FROM AUTHOR]

The paper presents brief results of comprehensive studies of the water area of the Tatar Strait and Sea of Japan obtained on cruise 61 of the R/V "Akademik Oparin" in November–December 2020. The bottom relief and geophysical and gas-geochemical fields were refined, and new features of the geochemistry and mineralogy of bottom sediments were revealed. [ABSTRACT FROM AUTHOR]

This paper reports the results of investigations in September 2017 on the radioecological state of bottom sediments of the East Siberian Sea during integrated research of the Siberian Arctic seas on cruise 69 of the R/V Akademik Mstislav Keldysh. Evaluation of the results of γ-spectrometric analysis found that the current specific activity of artificial cesium-137 in sediments is two orders of magnitude below the acceptable level and reflects the influence of global fallout from the atmosphere only. Sediments are not contaminated with heavy metals either. Bottom sediments are represented by silts: pelitic, aleuritic–pelitic, and fine aleuritic with a content of pelite (<0.01 mm) fractions of 40–80%. The western and eastern parts of the East Siberian Sea have differences in the distribution and composition of mineral components and element composition due to the influence of the catchments of the Indigirka and Kolyma rivers, respectively. [ABSTRACT FROM AUTHOR]

During cruise 73 of the R/V Professor Gagarinskiy and cruise 53 of the R/V Akademik Oparin, oceanographic studies of the Sea of Japan and Sea of Okhotsk and the Northwest Pacific were carried out. New data were obtained on the seafloor structure, water structure, and slope convection features in the Sea of Japan. [ABSTRACT FROM AUTHOR]

Multiyear monitoring of the marine environment of the Japan/East Sea was continued by the joint Korean–Russian expedition of the R/V Akademik Oparin (cruise 58) in October–November 2019, including changes in the sea circulation and ventilation and biogeochemical processes as a result of current climate changes and growing anthropogenic impacts. Studies of mesoscale eddies associated with the branches of the Tsushima Warm Current have been continued. Methane flare has been discovered for the first time at the eastern Primorye slope. [ABSTRACT FROM AUTHOR]

New data on the structure of the water column, upper layer of bottom sediments, and biological communities of the Gdansk and Gotland deeps and the Gulf of Finland in the Baltic Sea were obtained on cruise 55 of the P/V Akademik Ioffe (June 29–July 15, 2020). Hypoxic conditions developed below the permanent halocline, disturbed on the eastern slope of the Gotland Deep by inflow intrusions with a moderate oxygen content. Macrozoobenthos was absent in the deep parts of the Gdansk and Gotland Deeps. Cyanobacteria bloom was noted in the surface water layer during the entire expedition. [ABSTRACT FROM AUTHOR]

On cruise 82 voyage of the R/V Akademik M.A. Lavrentyev, comprehensive studies of ecosystems associated with hydrothermal vents and cold seeps in the Bering Sea were carried out. New data on the composition and structure of benthic communities of the Piip volcano were obtained. A new area of cold seeps has been discovered on the Chukchi slope of the Bering Sea. At present, the chemosynthesis communities of the Chukchi slope are the northernmost of their kind known in Pacific, and the Chukotka population of Calyptogena is the northernmost Recent population of pliocardiines in the World Ocean. [ABSTRACT FROM AUTHOR]

Abstract—The paper gives brief results of comprehensive studies in the South China Sea obtained from a joint Russian–Vietnamese expedition in November 2019 (cruise 88 of the R/V "Akademik M.A. Lavrentyev"). The set of methods included acoustics, geophysics, geology, mineralogy,geochemistry, paleogeography, geomicrobiology, hydrooptics and hydrology. The seafloor relief, geophysical and gasgeochemical fields have been refined; new features of the geochemistry and mineralogy of the continental shelf of Vietnam and the adjacent deep-sea basins have been revealed. [ABSTRACT FROM AUTHOR]

The 44th cruise of R/V Akademik Boris Petrov was carried out from October 5 to 30, 2018 in the Baltic Sea and Skagerrak Strait. The studies included investigation of the water column structure, bottom currents, bottom sediments, and biological communities. [ABSTRACT FROM AUTHOR]

The spatial variability of chlorophyll a concentrations was studied from the data of two near-shore expeditions and the cruise of the R/V Akademik M.A. Lavrent'ev in October-November 2010 over the northwestern part of the Sea of Japan. The sections across eddies showed a maximum of chlorophyll a at a depth of 40 m. According to the data from the cruise, the chlorophyll a concentration was maximum in the north of the sea and decreased to the south. In parallel, the procedures for chlorophyll a determination were compared for spectrophotometry with a fluorescence probe and a fluorescence flow system. The probe data of chlorophyll a fluorescence showed a high correlation with the chlorophyll a concentrations by spectrophotometry. On the contrary, data on chlorophyll a concentrations from spectrophotometry did not agree with those from the flow system. It was shown that a fluorimeter in the flow system recorded dissolved organic matter along with the chlorophyll a fluorescence. [ABSTRACT FROM AUTHOR]

The paper provides information about a complex of geological studies in Chaun Bay in the East Siberian Sea during cruise 60 of the R/V Akademik Oparin in October 2020. Preliminary results of the scientific expedition are discussed. [ABSTRACT FROM AUTHOR]

Data on the volcanic ash layers in 70 DSDP and ODP Sites and 100 cores obtained during cruises of the R/V Akademik Kurchatov and Mikhail Lomonosov were used for compiling tephrostratigraphic scale and schematic distribution maps of the pyroclastic material in the Quaternary sediments of the North Atlantic and Norwegian-Greenland Basin. It is revealed that the distribution of pyroclastic material through this region is characterized by cyclic and spatially irregular patterns. Based on their petrochemical and geochemical properties, these ashes are compared with the volcanics of Iceland and the Jan Mayen islands. The relations between the extreme climatic and cyclic explosive events are discussed. [ABSTRACT FROM AUTHOR]

The article focuses on the expedition on the ship R/V Viktor Buinitskii that was carried out from September to October 2012. The goal of the expedition was to map previously identified regions of anomalous gas yields in the Laptev Sea, Russia and to develop methods to quantify the volume of the releasing hydrocarbon gases.

New data on the geological structure and genesis of relict bottom relief forms, objects of underwater cultural heritage, and the structure of bottom sediments in the Baltic Sea were obtained during cruise 47 of the R/V Akademik Nikolaj Strakhov (June 25–July 4, 2020). Geomorphological features of submerged ancient coastal cliffs have been specified, large sand bodies have been identified at depths of 15–30 m, the iceberg origin of furrows has been confirmed, buried paleoincisions have been identified, gas chromatographic analysis of gas-saturated sediments has been performed, and a search for submerged objects has been carried out. [ABSTRACT FROM AUTHOR]

The article focuses on the utilization of seismoacoustic sub-bottom profiler SES-2000 deep in the in commercial cruises of the R/V Akademik Sergei Vavilov and Akademik Ioffe led by O. V. Levchenko. The negotiation with German Innomar Technologie GmbH is aiming to obtain high resolution seismoacoustic profiles for the identification of typical seismic facies. Moreover, the focus of teams during the expedition of Cruise no. 32 of the R/V Akademik Ioffe are seismoacoustics and bottom sediments.

New data on the formation of the bottom topography, bottom sediments, spatial structure and dynamics of waters of the Baltic Sea were obtained in cruise 42 of the R/V Akademik Nikolaj Strakhov (August 17–27, 2019). The distribution, morphology, and structure of large sand bodies on the Rybachy plateau were obtained. Additional data on the formation of the bottom topography and sedimentation under the influence of iceberg exaration and ice rafting at all stages of the Baltic Ice Lake were obtained. Numerous active gas craters (pockmarks) have been identified in the central part of the Gdansk Deep. [ABSTRACT FROM AUTHOR]

First results of the multidisciplinary expedition onboard the R/V Akademik Nikolaj Strakhov in the Barents Sea in August–September 2018 are presented. Hydrophysical sounding has been carried out on 41 stations, sampling of bottom sediments has been done using both grab and gravity corer. As a result of the geophysical investigations, areas with manifestations of current dangerous natural processes are identified. Four seismic bottom stations have been installed in the Pechora Sea. [ABSTRACT FROM AUTHOR]

The article focuses on a study on the measurements of bottom currents in underwater channels of the Atlantic during Cruise 36 of the Russian research vessel Akademik Sergey Vavilov. It states that the Conductivity–Temperature–Depth profiling of the Vema Channel, Romanche Fracture Zone and Kane Gap of the Antarctic Bottom Water, was performed using an SBE-19 (by Sea-Bird Electronics Inc.) profiler. It reports that the profiling revealed different orographic forms of the bottom topography.