“Comprehensive multidisciplinary research and monitoring of ecosystems of the Arctic Ocean and its seas” is one of the projects organized within the framework of the UN Decade of Ocean Science Program. One of the main goals of this program is to create an effective system for monitoring and forecasting the state of the marine environment, ensuring the accumulation and exchange of new knowledge about the nature, ecology and economy of the World Ocean for the sustainable development of economic activities and government decision-making. The research station “North Pole-41” based on the R/V “Severniy Polus” has been in the Arctic drift since the beginning of October 2022 in the waters of the Eurasian basin of the Arctic Ocean (AO). The scientific program of the expedition includes more than 50 types of research and observations, which are carried out on board the ship and in a scientific camp organized on the base ice field. The main goal of the work of the North Pole-41 station is to carry out complex interdisciplinary research in the “atmosphere–ice cover–ocean” system in the high latitudes of the Arctic Ocean in the annual cycle, aimed at identifying the patterns of action of the physical mechanisms responsible for the development of seasonal processes and the formation interannual changes in interacting geospheres. Thus, the North Pole-41 expedition is the main “springboard” for fulfilling the tasks of the UN Decade of Ocean Sciences Program in the Arctic Ocean. This article briefly summarizes information about the main research carried out during the expedition in 2022–2023.

The sustainable development and environmental protection of the Arctic ecosystem is on the agenda globally. The Convention of Biological Diversity (CBD) and the UN Sustainable Development Goals call for conserving at least 10 per cent of coastal and marine areas globally. Management tools to achieve this goal include marine protected areas (MPAs) and "other effective area-based conservation measures" (OECMs) of structural megabenthic organisms (e.g. corals, sea pens, sponges, anemones, etc.). But large areas of the ocean are lacking information about seabed communities. Here we show that this data gap can potentially be filled by collecting data on megabenthic organisms that are "bycatch" (not the target species) on government research vessels monitoring commercial fish and shellfish. For this paper, several Arctic and sub-arctic nations contributed megabenthos data from a total of 12.569 fish assessment trawls and associated bottom water temperature data. The latter outline areas of warm sub-Arctic inflow versus colder Arctic waters, which we align with temperature affinities of community. We also found that maximum levels of shared taxa were higher between Atlantic and Eurasian Arctic Seas than with Pacific Arctic Seas. Areas of high standardized species richness generally, but not everywhere, coincided with areas of high standardized biomass and/or high current velocity and in transition zones between water masses. We did not find that standardized taxon richness declined with latitude (from 60 to 81°N) as has been previously hypothesized. High biomass was generally associated with Arctic outflow shelves and/ or (within-region) colder water masses. We identify areas with high proportions of sessile and upright taxa that may be susceptible to damage by bottom trawl gear, taxa with calcareous skeletons that may be susceptible to ocean acidification, and 'cold-water' taxa that may be most vulnerable to ocean warming. Our results demonstrate the feasibility and value of international collaboration and cooperation in understanding large-scale patterns of Arctic megabenthic communities and providing scientific advice for management of human activities in the global Arctic ecosystem.

This study presents a sampling manual of megabenthos bycatch, based on long-term monitoring programms of bottom communities in North Atlantic and Arctic. The present guidance will provide high-quality, reliable, and complete data about benthic communities for conservation and protection of their habitats. This manual will help to optimize sampling and processing of megabenthos by-catches on board a research or fishing vessel and standardize information about megabenthos bycatches for the analysis. The results of the application of this guidance in domestic and foreign studies are discussed.

This paper presents data on species composition and peculiarities of distribution of Decapoda in the southern part of Kara Sea obtained during trawl surveys in 2012 and 2016. In total, 11 species of decapod crustaceans were collected. In the last decade the fauna has been enriched by the invasion of the snow crab Chionoecetes opilio. Brief information on the environmental conditions of occurrence and maps of distribution in the studied area are presented for each species. The highest values of species richness (up to 6 species per catch), biomass and abundance of decapods were detected on the western slope of Priyamal shallow at 50–150 m depth range. According to the patterns of distribution and environmental conditions, three groups of species were distinguished: associated with cold and salty waters of Novaya Zemlya Trough; inhabiting lower salinity waters with a wide temperature range of the Priyamal and Ob-Yenisei shallows; and a group that is widespread within the area in wide range of conditions. In comparison with the neighboring Barents Sea, the decapod fauna of the Kara Sea is qualitatively and quantitatively depleted. The obtained data on the distribution of individual species and ecological groups can be used for the background assessment of the state of the decapod fauna, including the period of population formation of the alien species.

In this paper, the distribution of polychaetes in the Laptev Sea and New Siberian shoal is analyzed based on 115 bottom trawl samples taken in August–October 2014. Polychaetes were the most species-rich group (83 taxa, 74 identified to the species level). Two faunistic assemblages of polychaetes, coastal and offshore ones, were distinguished. The boundary of their distribution did not coincide with the boundaries of assemblages defined for the other groups of the trawl zoobenthos. In the southwestern part of the Laptev Sea it coincided with the boundary between positive and negative near-bottom temperatures, and in the New Siberian shoal it coincided with a 28 PSU isohaline. The coastal assemblage was dominated by species that were widespread in the sea area. Only five carnivorous and detritovorous species were typical for the complex. The offshore assemblage included 26 characteristic species belonging to all trophic groups. Besides, the proportion of sparsely distributed species was much higher in the offshore assemblage compared to the coastal one.

Preliminary results of the Transarktika-2019 winter expedition in the Arctic Ocean on the R/V “Akademik Tryoshnikov” are presented. The expedition program included studies on meteorology, hydrology, hydrochemistry, hydrobiology, geology, geophysics and an extensive complex of ice measurements in the Northern Barents Sea from the drifting ice and from the ship. During the expedition, it was possible to complete a wide range of tasks. The data obtained comprise a unique material for a comprehensive study of the current state of the environmental conditions in the Barents Sea. This paper highlights the most significant preliminary results of multidisciplinary observations in various environments, which will be further comprehensively analyzed and published in separate thematic articles.

1 — State Scientifi c Center of the Russian Federation Arctic and Antarctic Research Institute, St. Petersburg, Russia 2 — Lomonosov Moscow State University, Moscow, Russia 3 — St. Petersburg State University, St. Petersburg, Russia 4 — Southern Scientifi c Center of the Russian Academy of Sciences, Rostov-on-Don, Russia 5 — Murmansk Marine Biological Institute, Kola Sciencetifi c Center, Russian Academy of Sciences, Murmansk, Russia 6 — VNIIOkeangeologiya, St. Petersburg, Russia 7 — Polar Geophysical Institute, Apatity, Russia

According to the results of surveys performed in the years 2003–2008, the species composition of the Peracarida (Crustacea, Malacostraca) fauna of the Barents Sea was determined. In total, 323 species were identified within the study area. Sixty-four species of Peracarida were noted for the Barents Sea for the first time. The most significant refinements concerned the orders Isopoda, Cumacea, and Tanaidacea. The main features of the quantitative distribution of Peracarida were revealed; it was found that the richest accumulations were confined to mixed silty–sandy bottom sediments of the shallow waters and the slopes of troughs. In the Barents Sea, eight Peracarida faunistic complexes have been identified, which are confined to specific environmental conditions. Generally, boreal–arctic species prevail in the biogeographic structure, the share of the boreal species exceeds that of the arctic species (28 and 21%, respectively). The zone of combining the ranges of the arctic and boreal species has shifted eastwards and northwards compared to the period of 1968–1970; this is a consequence of the ongoing “warm” hydrological period in the Barents Sea.

The total content of mercury was studied in marine water, sediments and benthic organisms in Billefjord, Isfjord and Gronfjord (Western Spitsbergen) in 2017. The samples were collected between 21 and 24 of July 2017 on-board RV “Dalnie Zelentsy” of Murmansk Marine Biological Institute. Total mercury content was measured at chemical-analytical laboratory of the Russian Scientific Center on Spitsbergen in Barentsburg. Total mercury concentration in the water did not exceed 10 ng/l in all fjords. In the surface sediments the highest concentrations of total mercury were found in Isfjord (median 55 ng/g d.w.) while the Billefjord sediments were characterised by the lowest concentrations (median 10.4 ng/g d.w.). This fact might reflect the differences in water circulation and therefore sediment accumulation peculiarities. Total mercury data were obtained for benthic organisms of various feeding modes. Generally mercury levels were comparatively low (median 12.2 ng/g w.w.), however the highest concentrations were measured in the benthic fauna of Isfjord, specifically in polychaetes Maldania sarsi (max. 49.2 ng/g w.w.). Mercury accumulation in benthic organisms predominantly depended on their trophic level in the ecosystem and location in the fjord: benthic detritus feeders accumulate more mercury (median 25.0 ng/gw.w.).

The total content of mercury was studied in marine water, sediments and benthic organisms in Billefjord, Isfjord and Gronfjord (Western Spitsbergen) in 2017. The samples were collected between 21 and 24 of July 2017 on-board RV “Dalnie Zelentsy” of Murmansk Marine Biological Institute. Total mercury content was measured at chemical-analytical laboratory of the Russian Scientific Center on Spitsbergen in Barentsburg.Total mercury concentration in the water did not exceed 10 ng/l in all fjords. In the surface sediments the highest concentrations of total mercury were found in Isfjord (median 55 ng/g d.w.) while the Billefjord sediments were characterised by the lowest concentrations (median 10.4 ng/g d.w.). This fact might reflect the differences in water circulation and therefore sediment accumulation peculiarities.Total mercury data were obtained for benthic organisms of various feeding modes. Generally mercury levels were comparatively low (median 12.2 ng/g w.w.), however the highest concentrations were measured in the benthic fauna of Isfjord, specifically in polychaetes Maldania sarsi (max. 49.2 ng/g w.w.). Mercury accumulation in benthic organisms predominantly depended on their trophic level in the ecosystem and location in the fjord: benthic detritus feeders accumulate more mercury (median 25.0 ng/gw.w.).

The first data were obtained on the total mercury content in hydrobionts and their habitat in Grønfjorden, Spitsbergen, at the waste discharge sites of the settlement of Barentsburg in early spring 2017. The Hg concentration was below the detection limit in the water and varied from 7.1 to 42.3 ng/g of dry weight in the bottom sediments. Mercury concentration in the hydrobionts increased toward the inner fjord and was higher near the mouth of the Grøndalen River, which flows into the fjord. Elevated Hg concentrations at the mouth of the Grøndalen River indicate that much of the toxic metal is brought to the inner part of the fjord with riverine runoff, and this Hg source is likely more important than the surface supply of Hg transferred from local surface pollution centers at Barentsburg. The Hg concentration depended on the position of the marine organisms in the trophic chain and was the highest in the detritophage mollusks Thyasira gouldi, Cardium sp., and Macoma calcarea , the specialized predatory sea snail Cryptonatica affinis , and the cod Gadus morhua , which is a benthosophage–secondary predator. The total Hg concentrations in the hydrobionts and their habitat in Grønfjorden were generally relatively low and close to the background one.

The first description of the quantitative and qualitative compositions of the littoral fauna of Grønfjorden Gulf during the winter and spring period is given. Granulometric analysis of the surface sediments of the littoral has been performed. Thirty invertebrate taxa that did not leave the littoral zone during wintertime and could survive complete freezing during ebb have been identified. Species diversity and population density of the invertebrates were shown to depend on the granulometric size composition of the surface sediments.