Vol 63, No 3 (2023)

Based on the results of the global oceanic reanalysis (GLORYS12.v.1), materials of hydrometeorological observations of the Roshydromet network in the Laptev Sea and the mouth of the Lena River, reviews of the ice processes in the Arctic Ocean by the Arctic and Antarctic Research Institute, this paper considers the features of the evolution of the Lena Polynya on the estuarine coast of the Bykovsky Arm in the warm period 1993–2019. The relationship between the timing of the formation of a polynya on the seashore of this arm with the dates of the beginning of the flood at the top of the Lena River delta has been revealed. The assumption is confirmed that the average growth rate of the Lena polynya in summer is determined by the timing of its formation – the earlier the flood begins, the earlier the polynya forms on the coast of the Bykovsky arm and the smaller the average rate its growth. It has been established that the process of warming in the mouth area of the Lena in 2008–2019 stabilized, as there are no significant trends in the characteristics of water and ice regimes. These regularities may be invariant for other mouths of the rivers of the Laptev Sea basin, and the obtained dependences can be used to improve the forecast of the dates of cleansing of the water area at the estuary seashore of the Lena from ice and planning icebreaking navigation along the route Tiksi port–Lena River.

Calculations were made of the runoff of dissolved organic carbon (DOC) into the Kara Sea with the waters of the Ob and Yenisei rivers. The estimates performed showed that the DOC runoff with the Yenisei waters (3.67 × 10⁶ tC/year) is less than the DOC runoff with the Ob waters (4.06 × 10⁶ tC/year), which is due to differences in the structure of the drainage basins and estuaries of these rivers. All previous published estimates show the opposite. The lack of the DOC content data during the maximum flood of the Yenisei does not let us calculate accurately the DOC runoff with its waters, but makes it possible to estimate its maximum and minimum values (3.11–4.18 × 10⁶ tC/year).

The concentrations and composition of hydrocarbons (HCs), aliphatic (AHCs), and polycyclic aromatic hydrocarbons (PAHs) in the Barents and Kara Seas were determined in the surface microlayer (SML, 300 µm thick), melting ice, and surface waters. Field material was collected in 80 and 83 cruises of the R/V Akademik Mstislav Keldysh in August 2020 and June 2021, respectively. In SML, HCs occur primarily in suspension. In the Barents Sea, the AHCs content in suspension was lower (31–96, 68 µg/l on average) compared with the Kara Sea (187–1051, 693 µg/L on average), where examination was carried out in the early summer season. In the Kara Sea, the AHCs concentrations in the SML were 3.6 times higher than in the dissolved form (89–270, 158 μg/L on average), while compared to the suspension of surface waters, they were almost 15 times higher. The accumulation of organic compounds also occurs in ice, but to a lesser extent than in SML. From the alkanes composition, the influence of autochthonous processes on HCs generation in melting ice is insignificant. The PAHs contents in suspension were also 4.8 times higher on average than in the dissolved form. An influence of combustion products of ship fuel on the composition of PAHs was traced by markers, which showed that in addition to phenanthrene, in all samples fluoranthene and pyrene dominated.

The question of the possibility of using meiobenthos to monitor the state of bottom sediments (BS) in the Baltic Sea, where bottom macrofauna are unstable due to hypoxia, is of interest. The parameters of meiobenthos and the physicochemical characteristics of BS and bottom water were studied, and the toxicity of BS was determined by the survival of the amphipod Gmelinoides fasciatus in 10-day tests for 11 stations in the brackish part of the Gulf of Finland (depths of 10–52 m). Principal component analysis revealed two factors explaining 67% of the variability of the variables, and groups of stations similar in terms of conditions. Factor 1 combined nine related variables (depth, metal concentrations and fraction of sand in BS, ratio of nematodes and copepods (N/C index) and survival of amphipods), and factor 2 combined four variables (organic matter and polyaromatic hydrocarbons in BS, phosphates in water and the number of meiobenthos). Thus, bioindication of the environment by meiobenthos is promising, but requires an integrated approach to be applied in monitoring.

Experiments were carried out on intravital otolith-tagging of juveniles of the ocellated blenny after transition to benthic life mode with Alizarin Red S. Marking at a dye concentration of 200 mg/L for 16–18 h at night, gave 100% formation of fluorescent marks with zero mortality of experimental individuals. Alizarin marks on the otoliths correspond to “stress” marks in the form of darker micro-increments, visible in transmitted light. The calculation of microincrements in the zone between two consecutive markings with an interval of 9 days confirmed the daily periodicity of their laying at this stage of development of the ocellated blenny. This allowed us to determine the period of hatching in natural conditions of juveniles in the Zhitkov Bay (Russky Island, the Peter the Great Bay, Japan sea). Hatching of larvae in 2017 in this species occurred, according to our estimates, from the last decade of March to the end of the second decade of April, with a peak in the first decade of April. Hatching begins even under the ice at a slightly negative water temperature of –1–0°C, but it proceeds mainly already at a temperature of 1–3°C, after the removal of ice from the bay. Taking into account the known timing of spawning of the ocellated blenny in the Peter the Great Bay (November–early December), we can state that the development of its eggs in this area is greatly slowed down at water temperatures below zero in December–March and can go on for 4–5 months, which is almost 3 times longer than the development time in more mild conditions of the south Hokkaido.

The structural features of the Olyutorsko-Kamchatka accretion region allow us to reconstruct two paleobasins for the Late Cretaceous-Paleogene time, separated and fenced off from the ocean by volcanic arcs. The features of the structure and composition of the complexes characterizing the fragments of the oceanic crust show that these basins had a different nature. The age of the fragments of the crust of the Lesnovsko-Iruneisky basin are Alb–Maastrichtian.Volcanites are represented by differentiated toleites of the N-MORB type, rarely intraplate basalts and enriched toleites of E-MORB. Fragments of the crust of the Vetlovsky basin are of age from the Campan–Maastrichtian to the Middle Eocene. Among the volcanites, basalts of N‑MORB are mainly developed, less often E-MORB and, in some structures, basalts of oceanic islands (OIB). Geodynamics in the Late Cretaceous–Cenozoic time for the Kamchatka and Olyutorsky segments differed, starting from the Campanian time.

At present the continental margin of the South-East Africa is in the process of actives search prospecting. However on like of the West African continental margins, where throughout its entire length discovered mainly liquid hydrocarbons, in researching region known on the whole only gas accumulations. The reason for this is most likely the Karoo complex formation dating at early Permian, which is widespread at the East African basins. Enormous reserves of coal contained in the section of the Karoo formation in different basins (basin Karoo in SAR). Complex Karoo extending from south-west to north-east and little by little reduced not only by thickness, but in the content of coal reserve in it. The regions where the complex reduced at the north – east of the South- East Africa, appeared oil accumulation, like as in Lamu basin (Kenia), Somali and etc. Large gas reserves are discovered at the continental margin of the South-East Africa in Rovuma basin, North Mozambique and South Tanzania. This basin is nearest neighbor just the Karoo basin. Today Mozambique becomes a gas State in the Indian Ocean.

A unique climate experiment was carried out to study the composition of the air and the characteristics of the underlying surface in the Russian sector of the Arctic and Siberia. Synchronized research onboard the RV Akademik Mstislav Keldysh and the unique scientific facility (USF) flying laboratory Tu-134 Optik were carried out in the South Kara Sea. Validation of airborne and satellite algorithms for calculating the characteristics of the sea surface layer was carried out in the cruise. For the first time on the Arctic shelf, data were obtained on the concentration of methane in the natural system of troposphere–atmospheric surface layer–water column–bottom sediments. The fluxes of greenhouse gases were simultaneously estimated from the shelf area and adjacent land. A related research of the conditions and processes of recent and ancient sedimentation was carried out in the South Kara Sedimentary Basin, where huge hydrocarbon (HC) reserves are localized.

Investigation of interannual and short-term variability of the water parameters in the Japan and Okhotsk seas and their ecological state were continued in the cruises No. 77 of the R/V Professor Gagarinskiy and No. 97 of the R/V Akademik M.A. Lavrentyev in fall-winter season of 2021. CTD profiling and water sampling for chemical analyses including methane and radioisotopes were implemented. A mooring of bottom autonomous station was deployed for 2.5 month. The long-term trend of the bottom water warming, eutrophication and acidification of the Japan Sea have been confirmed. The features of the fall-winter restructuring of the field of currents of the northern part of the Sea of Japan, the multifrontality of the Sakhalin upwelling structure, and the bimodality of the Primorye Current are shown.