During cruise 71 of the R/V Akademik Oparinm the radioecological state of the Pacific Ocean east of Japan and the Kuril Islands, as well as the seas of Okhotsk and Japan, was assessed in connection with polluted water discharge from the Fukushima-1 NPP. The results of the first samples of surface analysis showed a tritium content of 0.36–0.78 tritium units (0.04–0.09 Bq/L). The highest concentrations were found in the jet of the Kuroshio Current and in the area of the Southern Kuril Islands. Meanwhile, it is ten thousands time lower than the radio security norm. On the cruise, samples of water, bottom sediments, and marine biota were prepared to analyze radio isotopes of cesium, strontium, lead, radium, etc. A large volume of hydrographic, chemical, biological, gas-geochemical, and mercury measurements and samplings was obtained. Mooring systems were recovered and redeployed. New data on the water state and dynamics of the study region were obtained, as well as biogeochemical parameters and their interannual variability in association with climate change and increasing anthropogenic load.

The paper presents brief results of gas-geochemical and hydrometeorological studies of the outer water area of Peter the Great Bay (Sea of Japan), obtained as a result of a marine expedition study on the R/V Professor Gagarinskiy (cruise 83) in October–November 2022. Areal atmochemical measurements of climatically active gases (CH4, CO2, H2O vapor) and Hg(0) in the near layer of the atmosphere of the outer water area of Peter the Great Bay were performed for the first time. Gas geochemical fields in bottom sediments and water column are detailed. The current position of gas flares within the outer shelf of Posyet Bay is determined. Long-term stations for marine daily monitoring were carried out.

Information is provided on the results of gas geochemical and hydrometeorological studies of Amur and Ussuri bays, Sea of Japan, on cruises 84 and 85 of the R/V Professor Gagarinskiy in December 2022. For the first time for the winter period, synchronous measurements of greenhouse gases and atomic mercury were carried out in the surface marine boundary layer of Peter the Great Gulf, and new information was obtained on the seasonal characteristics of gas geochemical fields in the water column and bottom sediments.

Investigation of the interannual and short-term variability of the water parameters in the seas of Japan and Okhotsk and their ecological state were continued on cruises 77 of the R/V Professor Gagarinskiy and 97 of the R/V Akademik M.A. Lavrentyev in fall–winter 2021. CTD profiling and water sampling for chemical analyses, including methane and radioisotopes, were carried out. Autonomous bottom stations were moored for 2.5 months. Long-term trends of bottom water warming, eutrophication, and acidification of the Sea of Japan have been confirmed. The specific features of fall–winter restructuring of the field of currents in the northern Sea of Japan, multifrontality of the Sakhalin upwelling structure, and bimodality of the Primorye Current are shown.

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.

The results of gas geochemical and lithogeochemical studies of bottom sediments in the Tatar Strait trough (Sea of Japan) based on cruise data from the R/V Akademik M.A. Lavrentyev (LV-81 and LV-85) are presented. Anomalies of hydrocarbon gases (HCGs) and chemical elements in the surface bottom sediments were determined. It has been established that sediments with anomalous methane contents are significantly enriched in Mn, Sc, V, Co, Ni, Cu, As, Se, Mo, Cd, Sb, Te, Tl, and U, the coefficients of the concentration (Kc) of which are 1.3–5.9 times higher than similar values at other stations. The data obtained allow us to assume the presence of gas sources of hydrocarbon migration; the continental slope and deep-water area of the Tatar trough are promising for setting up detailed work on the assessment of the oil and gas potential and the gas hydrate content.

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.

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.

The results of research carried out on cruise 62 of the R/V Akademik Oparin from December 14 to 29, 2020 continued monitoring of the interannual variability of the Japan Sea water parameters, confirmed the long-term warming trend of bottom waters, revealed its slowdown during the last decade, demonstrated the formation of a cyclonic gyre in the northern part of the sea and development of upwelling, contributing to more intensive cooling of the sea surface layer. A detailed survey of a mesoscale eddy was carried out in the area of the Primorye Current. The hydrochemical parameters, zooplankton, and methane and tritium in various water structures were assayed. The mercury content in the atmospheric water layer was measured.

Hydrocarbons, in particular methane, in bottom sediments are able to form accumulations together with chemical elements and inorganic compounds. Such elements are indicators of the presence of hydrocarbons. Their establishment in certain areas of the water area can make a serious contribution to geological exploration. This paper examines the relationship of the areas of methane concentration and chemical composition of bottom sediments in the southern part of the Tatar strait and the northern circuit of the central depression of the sea of Japan. A connection of methane was found with elements such as S, Mn, Sr, Cu, Zn, Pb and Ni. The strong correlation of methane with S. There is a medium and weak connection of methane with Cu, Zn, Mn, Ni, Sr. The main concentration of methane observed in the western part of Terney trough and on uplift-shift disturbances of the 46th parallel. Installed indicator elements and geochemical studies can be used for further analysis of the distribution patterns of hydrocarbon deposits in the area.

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.

В ноябре 2019 г. в Южно-Китайском море (исключительная экономическая зона СРВ) впервые за последние 30 лет была проведена крупная комплексная геолого-геофизическая совместная экспедиция ТОИ ДВО РАН и Вьетнамской академии наук и технологий (88-й рейс НИС «Академик М.А. Лаврентьев»). Области изучения – геофизика, геология, гидроакустика, газогеохимия, гидрооптика, геомикробиология, палеогеография и гидрология. В толще вод и донных отложениях впервые обнаружены газогеохимические аномалии, сравнимые с аномалиями над нефтегазоносным шельфом о-ва Сахалин. Впервые в районе исследований выявлены геомикробиологические индикаторы углеводородных скоплений. Уточнены рельеф, геофизические поля, гидрологическая структура, особенности седиментации, палеогеографии и минералогии континентального шельфа Вьетнама и прилегающих глубоководных бассейнов. Предложено выделить тонкодисперсные карбонатно-глинистые осадочные отложения в самостоятельный минеральный ресурс. Выявлены районы, перспективные для поисков новых залежей нефти и газа, газогидратов, скоплений железо-марганцевых образований и др. Более 70 % научного состава экспедиции составляли молодые ученые. In November 2019, for the first time in 30 years, an integrated geological and geophysical joint expedition of the POI FEB RAS and the Vietnamese Academy of Science and Technology was carried out in the South China Sea (EEZ Vietnam) (88 cruise of the R/V “Akademik M.A. Lavrent’yev”). The set of methods consisted of geophysics, geology, hydroacoustics, gasgeochemistry, hydrooptics, geomicrobiology, paleogeography and hydrology. Gasgeochemical anomalies were found in the water column and bottom sediments, comparable with the anomalies over the oil and gas deposits along the Sea of Okhotsk shelf of Sakhalin Island. For the first time in the study area, deep water geomicrobiological indicators of hydrocarbon accumulations have been identified. The relief, geophysical fields, hydrological structure, features of sedimentation, paleogeography and mineralogy of the continental shelf of Vietnam and the adjacent deep sea basins are refined. Finely dispersed carbonate-clay sediments were proposed as a new mineral resource. Areas that are promising for the search for new deposits of oil and gas, gashydrates, accumulations of iron-manganese formations, and others are identified. Young scientists occupied more than 60 % of the scientific expedition staff.