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The modern Arctic is characterized by a decreased ice cover and significant interannual variability. However, the reaction of the High Arctic ecosystem to such changes is still being determined. This study tested the hypothesis that the key drivers of changes in phytoplankton are the position and intensity of Atlantic water (AW) flow. The research was conducted in August 2017 in the northern part of the Barents Sea and in August 2020 in the Nansen Basin. In 2017, the Nansen Basin was ice covered; in 2020, the Nansen Basin had open water up to 83° N. A comparative analysis of phytoplankton composition, dominant species, abundance, and biomass at the boundary of the ice and open water in the marginal ice zone (MIZ) as well as in the open water was carried out. The total biomass of the phytoplankton in the photic layer of MIZ is one and a half orders of magnitude greater than in open water. In 2017, the maximum abundance and biomass of phytoplankton in the MIZ were formed by cold-water diatoms Thalassiosira spp. (T. gravida, T. rotula, T. hyalina, T. nordenskioeldii), associated with first-year ice. They were confined to the northern shelf of the Barents Sea. The large diatom Porosira glacialis grew intensively in the MIZ of the Nansen Basin under the influence of Atlantic waters. A seasonal thermocline, above which the concentrations of silicon and nitrogen were close to zero, and deep maxima of phytoplankton abundance and biomass were recorded in the open water. Atlantic species—haptophyte Phaeocystis pouchettii and large diatom Eucampia groenlandica—formed these maxima. P. pouchettii were observed in the Nansen Basin in the Atlantic water (AW) flow (2020); E. groenlandica demonstrated a high biomass (4848 mg m−3, 179.5 mg C m−3) in the Franz Victoria trench (2017). Such high biomass of this species in the northern Barents Sea shelf has not been observed before. The variability of the phytoplankton composition and biomass in the Franz Victoria trench and in the Nansen Basin is related to the intensity of the AW, which comes from the Frame Strait as the Atlantic Water Boundary Current. [ABSTRACT FROM AUTHOR]

The Arctic experiences remarkable changes in environmental parameters that affect fluctuations in the surface energy budget, including radiation and sensible and latent heat fluxes. Cold air masses and cloud transformations during marine cold air outbreaks (MCAOs) substantially influence the radiative fluxes, thereby shaping the link between large-scale dynamics, sea ice conditions, and the surface energy budget. In this study, we investigate various cloud characteristics during intense MCAOs over the Barents Sea from 2000 to 2018 using satellite data. We identify 72 intense MCAO events that propagated southward using reanalysis data of the surface temperature and potential temperature at the 800 hPa level. We investigate the macro- and microphysical parameters and radiative properties of clouds within selected MCAOs, their dependence on sea ice concentration, and their initial air mass properties using satellite data. A significant increase in low-level clouds near the ice edge (up to +25% anomalies) and a smooth transition to upper-level clouds is revealed. The total cloud top height during intense MCAOs is generally 500–700 m lower than under neutral conditions. MCAOs induce a positive net cloud radiative effect, which peaks at +20 W m−2 (100 km from the ice edge) and gradually decreases towards the continent (−2.3 W m−2 per 100 km). Our study provides evidence for the importance of changes in the cloud radiative effect within MCAOs, which should be accurately simulated in regional and global climate models. [ABSTRACT FROM AUTHOR]

Changes in the masses of icebergs due to deterioration processes affect the drift of icebergs and should be taken into account when assessing iceberg risks in the areas of offshore development. In 2022 and 2023, eight laboratory experiments were carried out in the wave tank of the University Centre in Svalbard to study the melting of icebergs in sea water under calm and rough conditions. In the experiments, the water temperatures varied from 0   ℃ to 2.2   ℃ . Cylindrical iceberg models were made from columnar ice cores with a diameter of 24 cm. In one experiment, the iceberg model was protected on the sides with plastic fencing to investigate the iceberg's protection from melting when towed to deliver fresh water. The iceberg masses, water temperatures, and ice temperatures were measured in the experiments. The water velocity near the iceberg models was measured with an acoustic Doppler velocimeter. During the experiments, time-lapse cameras were used to describe the shapes and measure the vertical dimensions of the icebergs. Using experimental data, we calculated the horizontal dimensions of icebergs, latent heat fluxes, conductive heat fluxes inside the iceberg models, and turbulent heat fluxes in water as a function of time. We discovered the influence of surface waves and water mixing on the melt rates and found a significant reduction in the melt rates due to the lateral protection of the iceberg model using a plastic barrier. Based on the experimental data obtained, the ratio of the rates of lateral and bottom melting of the icebergs and lateral melting of the icebergs under wave conditions was parametrized depending on the wave frequency. [ABSTRACT FROM AUTHOR]

Provenance study plays an important role in paleogeographic and tectonic reconstructions. Detrital zircons are commonly used to identify sediment provenance; however, a wide range of detrital zircon ages in clastic rock often represent a fingerprint of reworked older terrigenous successions rather than ages of magmatism and metamorphism in the provenance area. This study focuses on the provenance of detrital rutile grains in the Triassic–Jurassic sandstones from Franz Josef Land and shows the importance of multiproxy approaches for provenance studies. Trace element data demonstrate that most rutile grains were sourced from metapelitic rocks, with a subordinate population having a metamafic origin. The Zr-in-rutile thermometer and U-Pb geochronology suggest that detrital rutile grains were predominantly derived from rocks that underwent amphibolite facies metamorphism during the Paleozoic era, with a predominance of the Carboniferous–Permian ages. Therefore, we suggest that the provenance area for the studied sandstones on Franz Josef Land has a similar geological history to the Taimyr region and Severnaya Zemlya archipelago. We propose that this crustal domain extends across the Kara Sea and forms the basement to the north and east of FJL, representing a proximal provenance for the studied Mesozoic terrigenous rocks. This domain experienced both Middle–Late Ordovician and Carboniferous–Permian metamorphism. The comparison of U-Pb dating and the geochemistry of rutile, U-Th/He, and U-Pb dating of zircons showed that detrital rutiles are the powerful toll in provenance restoration and can give additional constrains when a provenance area locates within collisional-convergent settings. [ABSTRACT FROM AUTHOR]

Simple Summary: Seafood by-products contain a variety of valuable components, including bioactive peptides and essential fatty acids. The red king crab is a large, commercially important crustacean supporting profitable fisheries in the Barents Sea. In Norway, female red king crabs are included in the fishery. Large adult females carry egg masses, but red king crab eggs have not yet been studied for fatty acid content. In this paper, we provide information regarding the fatty acid profiles of red king crab eggs. We found a higher proportion of polyunsaturated fatty acids in comparison to saturated and monounsaturated fatty acids. Total pools of fatty acid did not differ significantly in terms of the stage of embryo development, female size, limb injury status, and habitat conditions. Individual comparisons, however, indicated significant differences for some fatty acids, providing evidence that they may play a role in physiological processes. Red king crab eggs may be considered a product with high nutritional value and are recommended for wide use in the food, pharmaceutical, and biomedical industries. The red king crab, Paralithodes camtschaticus, was introduced into the Barents Sea where, after a period of 30 years of adaptation, it has established a new population. This population has been commercially exploited over the past two decades, supporting profitable fisheries in both Russia and Norway. Biochemical studies aimed at assessing fatty acid profiles have been conducted, focusing primarily on the edible parts of red king crabs. Only recently have by-products been included in this research. Capture of female red king crabs is prohibited in Russia but is allowed in Norway. The fatty acids of the egg masses carried by these females have not yet been studied. To fill this knowledge gap, we assayed the fatty acid composition of eggs using gas–liquid chromatography. Our results showed a predominance of polyunsaturated fatty acids, while the concentrations of saturated and monounsaturated fatty acids were similar. Multivariate comparisons showed no significant differences in fatty acid profiles in terms of egg developmental stage (nauplius vs. metanauplius), habitat conditions (soft vs. hard bottoms), female size class, or number of autotomized limbs. However, individual comparisons showed some differences in fatty acids, the most important being the lower content of docosahexaenoic acid in eggs at the metanauplius stage compared to eggs at the nauplius stage, which is likely due to its essential role in the development of red king crab embryos. The total fatty acid content (53.94 mg g−1) was 2–87 times higher in eggs than in other red king crab tissues, confirming the critical role that fatty acids play in maintaining physiological processes during vitellogenesis. The high content of essential fatty acids and an optimal omega-3-to-omega-6 ratio (4.9) suggest that red king crab eggs are a good product for a healthy diet and a valuable source for extracting essential fatty acids. [ABSTRACT FROM AUTHOR]

Simple Summary: The adductor muscles of scallops are highly prized for their exceptional taste and nutritional value. Additionally, by-products of scallops show potential for the production of functional foods, animal feed, and nutraceuticals. To address the paucity of information regarding the amino acid composition of Iceland scallops from the coastal Barents Sea, we conducted biochemical analyses of various tissues from this species. Our findings revealed the highest contents of glycine and arginine, two amino acids widely implicated in the physiological processes of scallops worldwide. The consistency of amino acid composition across the muscle, gonad, and mantle tissues, as well as their lack of differentiation between male and female scallops, was noteworthy. A negative correlation was observed between the gonad index and amino acid contents in the muscle, while a positive relationship was found between muscle amino acid content and depth. Furthermore, amino acid contents in the mantle demonstrated a positive correlation with water temperature. Scallop by-products hold significant promise for the food and pharmaceutical industries. The Iceland scallop from the Barents Sea is a commercially important species with promising aquaculture potential, but information on the biochemical properties of its tissues is limited. Our analysis of the adductor muscle, gonad, and mantle of this bivalve mollusk from coastal waters provided insight into its amino acid composition. Biochemical analysis revealed predominant levels of glycine (11.8, 11.5, and 9.6 mg g−1, respectively) and arginine (11.2, 8.3, and 5.8 mg g−1, respectively). While multivariate comparisons did not reveal significant differences in amino acid composition between the tissues, single comparisons showed significantly higher levels of arginine and leucine in the adductor muscle compared to those of the mantle. The abundant presence of glycine and arginine underscores their importance in maintaining basic physiological processes, consistent with other scallop species. Redundancy analysis identified water depth and scallop gonad index as influential factors shaping the amino acid profile in the adductor muscle. In the case of the mantle, water temperature emerged as the main driver of amino acid content. Our results confirm the richness of essential amino acids in scallop by-products and highlight their potential for human consumption, production of feed ingredients for farmed animals, and nutraceuticals. [ABSTRACT FROM AUTHOR]

Simple Summary: Information on epibionts and symbionts of the introduced Barents Sea red king crab during the winter period is currently lacking. To address this gap, we examined the species composition and infestation indices of epibionts on this host in the northern part of Kola Bay in November. Our findings indicate a higher infestation rate of barnacles and amphipods during the winter season compared to the summer. In contrast, infestation rates of other species remained low during winter, reflecting seasonal fluctuations in both the size distribution of red king crabs and prevailing temperature conditions. Our research provides novel data on the growth patterns of commonly associated organisms, which could prove invaluable in determining the age of red king crabs in the Barents Sea. The species composition of epibiotic communities on red king crab was investigated in Sayda Bay, Russia, during November of 2015 and 2016. The community consisted of 12 species in total. Among epibionts, the barnacle Balanus crenatus was most prevalent (67.0%), while the amphipod Ischyrocerus commensalis was the most frequent symbiont (77.3%). Infestation levels in May–June 2005 and September 2004 were higher, as a larger proportion of small crabs without fouling species were present during those seasons. The lower infestation intensities recorded for other common associated organisms during winter can be attributed to their increased mortality due to unfavorable temperature conditions. The localization of epibionts and symbionts were related to larval settlement patterns of attached species and feeding behavior of mobile species. Monthly growth increments for I. commensalis and B. crenatus were estimated at 2 mm in body length and 1.35 mm in basal diameter, respectively. Size-at-age data for epibionts can aid in the age determination of large male crabs that may skip an annual molt. [ABSTRACT FROM AUTHOR]

The seasonally ice-covered marine region of the European Arctic has experienced warming and sea ice loss in the last two decades. During expeditions in August 2020 and 2021, new data on size-fractioned primary production (PP), chlorophyll a concentration, phytoplankton biomass and composition and carbon fixation rates in the dark were obtained in the marginal ice zone (MIZ) of the Barents Sea, Nansen Basin and Greenland Sea to better understand the response of Arctic ecosystems to ongoing climate changes. Four different situations were observed in the study region: (i) a bloom of the large-cell diatom Podosira glacialis, whose biomass was trapped in a strong halocline at the edge of a dense ice cover; (ii) a bloom of the chain-like colonies of Thalassiosira diatoms on the shelf in mixed waters in fields of shallow ice that could be supported by "fresh" elements in the polynya condition, as well as by terrestrial run-off and drifting ices; at the late stage, this bloom was accompanied by intensive growth of Phaeocystis pouchetti; (iii) dominance of small-cell phytoplankton under weakened stratification and the significant influence of the Atlantic water, depleted of microelements and silicates; (iv) dominance of dinoflagellates of eutrophic water in the contact zone between the water masses of Arctic origin and Atlantic origin in clear water under conditions of increased light intensity. The >10 µm phytoplankton cell size group increased its relative contribution to PP as a response to stratification, light and nutrient load associated with sea ice conditions. Small phytoplankton with sizes < 2 µm formed the basis of total PP in the MIZ regardless of the state of the sea ice. [ABSTRACT FROM AUTHOR]

Simple Summary: Of all the Arctic seas, the prokaryotic communities of the Barents Sea are the most affected by climate change and are strongly influenced by microbiota from the Atlantic Ocean. Using 16S metabarcoding, we analyzed samples of prokaryotic plankton communities in the Barents Sea and found two types of communities. The origin of these communities is discussed in terms of biogeography. The Barents Sea is one of the most rapidly changing Arctic regions, with an unprecedented sea ice decline and increase in water temperature and salinity. We have studied the diversity of prokaryotic communities using 16S metabarcoding in the western and northeastern parts of the Barents Sea along the Kola Section and the section from Novaya Zemlya to Franz Joseph Land. The hypothesis-independent clustering method revealed the existence of two distinct types of communities. The most common prokaryotic taxa were shared between two types of communities, but their relative abundance was different. It was found that the geographic location of the sampling sites explained more than 30% of the difference between communities, while no statistically significant correlation between environmental parameters and community composition was found. The representatives of the Psychrobacter, Sulfitobacter and Polaribacter genera were dominant in samples from both types of communities. The first type of community was also dominated by members of Halomonas, Pseudoalteromonas, Planococcaceae and an unclassified representative of the Alteromonadaceae family. The second type of community also had a significant proportion of Nitrincolaceae, SAR92, SAR11 Clade I, NS9, Cryomorphaceae and SUP05 representatives. The origin of these communities can be explained by the influence of environmental factors or by the different origins of water masses. This research highlights the importance of studying biogeographic patterns in the Barents Sea in comparison with those in the North Atlantic and Arctic Ocean prokaryote communities. [ABSTRACT FROM AUTHOR]

Simple Summary: The warming of Arctic regions has led to an increase in extended ice-free periods in the continental shelf of the northeastern Barents Sea. A study on the Makarov Strait in the southwestern part of the St. Anna Trough in autumn 2019 investigated the effect of this process on the structure and functioning of benthic communities. It was found that the biodiversity and structure of local macrozoobenthos were connected with the duration of ice-free periods because this variable influenced vertical carbon flux and was found to be the primary predictor for faunal abundance and diversity indices. Two faunal groups were identified, corresponding to short and long open-water periods. Our results may have important implications for the conservation and monitoring of this region. The continental shelf of the northeastern Barents Sea is presently experiencing a weak influx of Atlantic water from the west. In recent times, warming in Arctic regions has led to an increase in extended ice-free periods in this area, instead of significantly elevating water temperatures. The implications of this phenomenon on the structure and functioning of benthic communities were investigated during the autumn of 2019 within the Makarov Strait, located in the southwestern part of the St. Anna Trough. The macrozoobenthic communities exhibited a clear connection with the duration of ice-free periods. This variable influenced a vertical carbon flux, which subsequently served as the primary predictor for faunal abundance and diversity, as demonstrated by redundancy and correlation analyses. Two faunal groups were identified, corresponding to short and long open-water periods. Both groups had similar alpha diversity (65 ± 6 and 61 ± 9 species per station) and biomasses (39 ± 13 and 47 ± 13 g m−2) but displayed differing abundances (1140 ± 100 vs. 4070 ± 790 ind. m−2) and other diversity indices. We observed a decline in the proportion of polychaetes, accompanied by an increase in the proportion and diversity of bivalves, as well as a rise in the abundance of infaunal species, sub-surface deposit feeders, and mobile suspension feeders, in response to the increasing vertical carbon flux. The potential increase in anthropogenic pressures related to oil development in the northeastern Barents Sea highlights the importance of our study for conservation and monitoring efforts in the region. [ABSTRACT FROM AUTHOR]

The biodiversity of Cephalaspidea (Gastropoda: Heterobranchia) is poorly studied, and novel findings often lead to revisions at different taxonomic levels. The family Philinidae has a distinct set of defining characters in the shell, copulatory apparatus, and gizzard morphology, but several species, considered part of the family, deviate from it significantly. Philine denticulata (J. Adams, 1800) was considered to be a Philinidae despite the species morphology not fitting well with the family diagnosis. This species has an oval cylindrical external shell, jaws, and a gizzard lined with a chitinous layer with three thickened ridges. We studied Philine denticulata morphology on samples from the White and Barents Seas using the light and scanning electron microscopy methods in addition to computer microtomography. We also reconstructed its phylogenetic position using COI, 16S, 28S, and H3 genetic markers. Our integrative analysis revealed close relationships of this species to the family Aglajidae. Thus, we describe a new genus Philinissima gen. nov., including a single species Philinissima denticulata (J. Adams, 1800) comb. nov. which is the first aglajid registered from the Arctic waters. Our findings highlight possible problems in the Aglajidae taxonomical composition and an overall need for a dedicated integrative revision of the Cephalaspidea. [ABSTRACT FROM AUTHOR]

Simple Summary: Bryozoans are predominantly short-lived sessile organisms inhabiting both living and dead hard substrates. This group is considered a good biological indicator of environmental conditions. The Svalbard Archipelago is located at high latitudes, and the local benthic communities are affected by severe environmental conditions. In general, the bryozoan fauna in this region has been well studied, albeit to varying spatial degrees. Information regarding Grønfjorden is scarce and, therefore, we aimed to study species composition, diversity, and biomass of bryozoans in this glacier fjord. We found a rather diverse fauna with low biomasses for all species. Cluster analysis distinguished two groups of stations: one with lower diversity and biomass in warmer water, and the other with higher values in colder water. The most important factors shaping the bryozoan communities were water temperature and the proportional occurrence of macrophytes. Taking into account ongoing climate change, our results may be useful for further monitoring the effects of elevated temperatures on benthic organisms in the Arctic. Despite significant research efforts focused on benthic assemblages in West Spitsbergen, there is a lack of knowledge regarding the shallow water bryozoan communities in Grønfjorden, a glacier fjord belonging to the Isfjorden system, Norway. Here, we studied species composition, richness, distribution, and biomass of bryozoans in the intertidal and upper subtidal zones of Grønfjorden in summer. We found 62 bryozoan species, among which Celleporella hyalina (Linnaeus, 1767), Harmeria scutulata (Busk, 1855), and Tegella arctica (d'Orbigny, 1853) were most prevalent while the highest contributions to the total biomass were registered for Eucratea loricata (d'Orbigny, 1853), Tricellaria gracilis (Van Beneden, 1848), Turbicellepora incrassata (Lamarck, 1816), and Tricellaria ternata (Ellis and Solander, 1786). Alpha-diversity varied from 1 to 50 averaging 15.1 ± 2.6 species. Bryozoan biomass ranged from 0.008 to 10.758 g m−2 with a mean value of 2.67 g m−2 being lower than in the central and northern parts of the Barents Sea. For the first time, we registered the presence of the circumpolar bryozoan Amathia arctica in Svalbard waters probably as a result of stronger advection of Atlantic water into the fjord. Cluster analysis revealed two groups, mainly composed of stations in colder and warmer waters. A relatively high proportion of outlying stations reflected habitat heterogeneity in Grønfjorden. Redundancy analysis indicated that bryozoan diversity and biomass were strongly negatively associated with temperature. A positive relationship was found between bryozoan biomass and the proportional contribution of macrophytes to a pool of substrates. Our study provides a reference point for further monitoring of changing marine ecosystems at high latitudes. [ABSTRACT FROM AUTHOR]

Simple Summary: Invasive red king crabs support a large-scale fishery in the Barents Sea, but, currently, their by-products are not used by the food and pharmaceutical industries, partly because information regarding the biochemical content of the by-products is scarce or absent. For this reason, we assayed fatty acid profiles in the ovaries and testes of adult red king crabs. We found a predominance of polyunsaturated fatty acids and lower levels of saturated and monounsaturated fatty acids. Female gonads showed higher levels of fatty acids than male gonads due to higher levels of energy allocation to reproduction processes in females, which have larger and heavier gonads but smaller and lighter bodies than males. Ovaries are characterized by excellent quality in terms of the high content of essential fatty acids and could be recommended for consumption and as a source of valuable substances. Red king crab (Paralithodes camtschaticus) is a large shelf species native to the Pacific Ocean. Due to its high commercial value, this species was introduced into the Barents Sea, where it has formed a new population that now supports a stable commercial fishery. Information on fatty acid profiles in different tissues of the Barents Sea P. camtschaticus is scarce. For this reason, the gonads of red king crabs collected at a coastal site in the Barents Sea during the summer were analyzed for fatty acid composition by gas-liquid chromatography. The proportions of total saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids in the ovaries of P. camtschaticus were 25.9 ± 2.0%, 22.5 ± 2.3%, and 51.6 ± 2.5%, respectively; in the testes, these levels accounted for 35.1 ± 5.7%, 19.1 ± 2.0%, and 45.8 ± 4.5%, respectively. Fatty acid profiles were similar in larger and smaller red king crabs and crabs with old and new shells. Concentrations of fatty acids were higher in ovaries compared to testes, reflecting higher reproductive efforts in female red king crabs. High levels of docosahexaenoic and eicosapentaenoic fatty acids detected in the ovaries of red king crabs from the Barents Sea indicate that these gonads can be a good alternative source for these fatty acids in the human diet and/or for extracting important fatty acids for use in the medical and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

This study aimed to confirm the hypothesis of a floristic identity between the southeastern Barents Sea and the southwestern Kara Sea. We conducted integrated studies of pelagic microalgae communities including microscope cell counting and taxonomical identification as well as photosynthetic pigments determination and defining of hydrological and hydrochemical characteristics during a cruise in late August and the first half of September 2020. As far as we are concerned, no such observations had been carried out in this region at this time of the year before. During our observations, 35 species were identified, 14 (40%) of which were present in both water bodies. The communities of both regions were in a state corresponding to the autumn stage of the annual succession cycle. In the southeastern Barents Sea, the mean abundance of organisms in the water column varied from 10.650 to 41.840 cells per liter with a biomass of 71.04 to 300.55 µg/L. In the southwestern Kara Sea, these values were 3.510–28.420 cell/L and 16.31–66.96 µg/L, respectively. In general, the results of a comparative analysis suggest that the pelagic algal communities in the regions under comparison, despite the difference in hydrological parameters, demonstrate similar qualitative and quantitative characteristics and thus may belong to the same phytogeographic region. [ABSTRACT FROM AUTHOR]

Cryogenic soils are the most important terrestrial carbon reservoir on the planet. However, the relationship between soil microbial diversity and CO2 emission by cryogenic soils is poorly studied. This is especially important in the context of rising temperatures in the high Arctic which can lead to the activation of microbial processes in soils and an increase in carbon input from cryogenic soils into the atmosphere. Here, using high-throughput sequencing of 16S rRNA gene amplicons, we analyzed microbial community composition and diversity metrics in relation to soil carbon dioxide emission, water-extractable organic carbon and microbial biomass carbon in the soils of the Barents Sea archipelagos, Novaya Zemlya and Franz Josef Land. It was found that the highest diversity and CO2 emission were observed on the Hooker and Heiss Islands of the Franz Josef Land archipelago, while the diversity and CO2 emission levels were lower on Novaya Zemlya. Soil moisture and temperature were the main parameters influencing the composition of soil microbial communities on both archipelagos. The data obtained show that CO2 emission levels and community diversity on the studied islands are influenced mostly by a number of local factors, such as soil moisture, microclimatic conditions, different patterns of vegetation and fecal input from animals such as reindeer. [ABSTRACT FROM AUTHOR]

The rapid response of benthic foraminifera to organic carbon flux to the seafloor makes them promising bioindicators for evaluating the organic carbon stored in marine sediments. Fjords have been described as hotspots for carbon burial, potentially playing a key role within the carbon cycle as climate regulators over multiple timescales. Nevertheless, little is known about organic carbon-rich sediments in Arctic open shelves and their role in global carbon sequestration. To this aim, four sites have been sampled along a W-E transect across the Kveithola Trough located in the NW Barents Sea. Living (stained) benthic foraminiferal density, biodiversity and vertical distribution in the sediment were analysed together with the biogeochemical and sedimentological data. We identified two main depositional environments based on the relationship between benthic foraminiferal assemblages and carbon content in the sediments: (1) an oligotrophic land-derived organic matter region located in the outer part of the trough influenced by the warm and saline Atlantic Water; and (2) a stressed eutrophic environment, with high-content of metabolizable organic matter in the inner part of the trough, which comprises the main drift and the Northern flank of the trough. The freshness and good nutritional quality of the organic matter detected in the inner region could be the result of the better preservation of the organic matter itself, basically driven by the rapid burial of fine-grained organic-rich sediments enhanced by the cold and less saline Arctic Water coming from the Barents Sea. We conclude that foraminifera provide a tool to describe the Kveithola depositional environment as a carbon burial hotspot in a changing Arctic area subjected to a pulse of fresh food intended as biopolymeric carbon. [ABSTRACT FROM AUTHOR]

The isotopic parameter δ18O in oceanography is used for the calculation of mixing proportions of the Atlantic, rivers, and melted waters as well as the relative content of ice-forming waters. Using these values, as well as nutrient concentrations in the nuclei of these waters, it is possible to calculate a conservative concentration, which is determined only by the water's mixing. These values are the points of reference for water nutrients reserve changes at the expense of the «nonconservative» factors (photosynthesize and geochemical sedimentation). This approach in the calculation of primary production allows moving from the use of the constant stoichiometric ratios to the floating ones, which is observed in the actual ecosystem. Based on the proposed method, the nutrient consumption features and production changes in the Barents Sea were studied. According to the maximum value of production in the summer, the following areas were identified—an early autumn period in the Barents Sea, an area with the maximum values of gross primary production (GPP > 150 g C m−2), three regions with increased values (GPP > 100 g C m−2), and two regions with relatively low values (GPP < 100 g C m−2). The use of this technique with a long-term data series available on salinity and the content of nutrients will allow the future to proceed to the study of the climatic variability of these parameters, ranging from the nutrient consumption variability to the productivity variability of the study area. [ABSTRACT FROM AUTHOR]

Simple Summary: Phytoplankton and other algae form the bases of food webs in aquatic systems as they convert solar energy into chemical compounds that are consumed by the higher trophic levels. Through the photosynthesis process based on chlorophyll a (Chl-a), phytoplankton uses sunlight to take carbon dioxide and release oxygen. Chl-a is a good indicator of phytoplankton biomass and may be used to detect changes in marine ecosystems due to environmental fluctuations. Dramatic climatic changes have been observed in the Arctic during the past decades. The study aimed to give up relations between Chl-a and climatic factors in the Barents Sea. We found an increase in Chl-a over the last four decades, with maximum values in warm periods. High temperature and a decline in sea ice extent were associated with greater Chl-a concentrations. Atmospheric processes estimated through the North Atlantic Oscillation indices strongly affected the surface water temperature, salinity, and Chl-a. Mapping of the Barents Sea showed high concentrations of Chl-a associated with the ice edge in spring and coastal waters in summer. Our study suggests that spatial, seasonal, and temporal variability in Chl-a is controlled by temperature changes, ice extent, and global atmospheric circulation and may be used for future investigations dealing with climatic forcing in the Arctic marine systems. The Arctic climate strongly affects phytoplankton production and biomass through several mechanisms, including warming, sea ice retreat, and global atmospheric processes. In order to detect the climatic changes in phytoplankton biomass, long-term variability of chlorophyll a (Chl-a) was estimated in situ with the changes in the surface sea temperature (SST) and salinity (SSS) in the Barents Sea and adjacent waters during the period of 1984–2021. Spatial differences were detected in SST, SSS, and Chl-a. Chl-a increased parallel to SST in the summer-autumn and spring periods, respectively. Chl-a peaks were found near the ice edge and frontal zones in the spring season, while the highest measures were observed in the coastal regions during the summer seasons. SST and Chl-a demonstrated increasing trends with greater values during 2010–2020. Generalized additive models (GAMs) revealed that SST and Chl-a were positively related with year. Climatic and oceanographic variables explained significant proportions of the Chl-a fluctuations, with six predictors (SST, annual North Atlantic Oscillation index, temperature/salinity anomalies at the Kola Section, and sea ice extent in April and September) being the most important. GAMs showed close associations between increasing Chl-a and a decline in sea ice extent and rising water temperature. Our data may be useful for monitoring the Arctic regions during the era of global changes and provide a basis for future research on factors driving phytoplankton assemblages and primary productivity in the Barents Sea. [ABSTRACT FROM AUTHOR]

Coryne hincksi Bonnevie, 1898 (Cnidaria, Hydrozoa) is a rare corynid hydrozoan that was first found in the coastal Barents Sea on the surface of other hydrozoan species and on the body of spider crabs in 1913. After the introduction of red king crabs into the Barents Sea in the 1960s and their range expansion and population growth, colonies of C. hincksi were registered on this host as well. In this paper, we update a list of C. hincksi records on red king crabs and present a detailed description. Also, for the first time, we provide quality photographs of a living colony of this species. Despite relatively low prevalence rates (1.4–3.2% in certain years), currently in the Barents Sea, C. hincksi occurs on crustaceans thus exhibiting a predominantly symbiotic lifestyle. [ABSTRACT FROM AUTHOR]

Kola Bay is the most developed coastal area in the Russian part of the Barents Sea, but despite a long history of research, information about the local shallow-water benthic communities is lacking. For this reason, in this fjord area, we investigated the soft-bottom zoobenthos to determine its distribution and the factors influencing its abundance, biomass, and diversity. An analysis of 24 samples collected by divers at eight stations located at 7–8 and 10–15 m depths revealed 127 benthic taxa with an average abundance and biomass of 12,190 ± 4740 ind. m−2 and 30 ± 8 g m−2, respectively. The most severe abiotic conditions (high rates of sedimentation and eutrophication) were found at the head of the bay while the highest densities of predator red king crabs were registered in the middle part. The total benthic abundance and biomass, as well as the abundances of infauna, mobile taxa, subsurface deposit feeders, and surface deposit feeders, decreased towards the central part of the bay, reflecting gradients in the environmental conditions. In the inner part of the bay, we registered two communities: Cossura pygodactylata + Ciliatocardium ciliatum and Arctica islandica + Laonice cirrata, while the benthos of the middle part was less structured. Redundancy analysis indicated that the faunal abundances were influenced mainly by predator density (negative association) and the organic matter content (positive association). The total benthic biomass was negatively linked to water temperature due to the predominance of cold-water species in the area and a close positive association of this factor with crab abundance. In contrast, the highest diversity was registered at the warmer sites, which may have been a reflection of the borealization process in the Arctic. Our results contribute towards the proper management and conservation of the local benthic ecosystem and provide reference data for future monitoring programs and coastal management guidelines. [ABSTRACT FROM AUTHOR]

To provide a baseline description of copepod assemblages in the Pechora Sea, an estuarine area with great economical and ecological importance, we conducted a survey during the summer season. A total of 24 copepod taxa were identified in the study, with Acartia longiremis, Calanus finmarchicus, Centropages hamatus, Copepoda nauplii, Eurytemora affinis, Oithona similis, Pseudocalanus spp., and Temora longicornis being the most numerous. The high diversity (Shannon index = 2.51 ± 0.06), density (18,720 ± 3376 individuals m−3) and biomass (89 ± 18 mg dry mass m−3) of copepods were revealed. Populations of common small copepod taxa were dominated by the young stages, indicating spawning, while older copepodites prevailed among medium- and large-sized species, showing that their reproduction occurred before our survey. Cluster analysis indicated three groups of stations that mainly differed in the abundance of particular species. There were clear associations between copepod assemblages and environmental variables. Statistical analyses showed significant correlations between copepod abundance and water temperature or sampling depth, while other factors had a lesser influence. Our results suggest a strong effect of local circulation and currents on the spatial pattern of the copepod assemblages in the study area. This study may be useful for future biomonitoring in the south-eastern Barents Sea. [ABSTRACT FROM AUTHOR]

In this study, nematodes were first reported in the amphipods, Ischyrocerus commensalis, collected from the introduced and commercially important red king crabs, Paralithodes camtschaticus, in the coastal Barents Sea in July 2022. Commensal amphipods were registered on all red king crabs captured (n = 70, prevalence 100%). Further laboratory analysis revealed that 11 out of 467 amphipod individuals (prevalence 2.4%) harbored single third-stage larvae of Hysterothylacium sp. l. (Nematoda: Anisakidae). The nematode larvae ranged from 0.63 to 6.10 mm in body length. Due to the low prevalence of nematodes and lower vulnerability of the host amphipods to fish predators, negative effects on the Barents Sea ecosystem through the range expansion of crab-associated amphipods and their parasites are unlikely. [ABSTRACT FROM AUTHOR]

The biodiversity, infestation patterns, and spatial distribution of organisms living in association with the introduced red king crab Paralithodes camtschaticus were studied in Dalnezelenetskaya Bay, southern Barents Sea, in 2009–20013 to update a list of species, reveal long-term changes in this epibiotic community, and identify key factors affecting the prevalence and intensity of infestation. A total of 90 associated species were found throughout the study period, or twice as many as in 2004–2008, reflecting relatively low similarity between these periods. Half of the species were found on one to three crabs only. Copepods had the maximum diversity (23 species). For the first time, macroalgae were found as epibionts of red king crabs. Overall, the highest prevalences were found for the amphipod Ischyrocerus commensalis (74.2%), the copepods Tisbe furcata (57.7%) and Harpacticus uniremis (29.4%), the amphipod Ischyrocerus anguipes (27.3%), and the fish leech Johanssonia arctica (16.2%). Redundancy analysis showed that host size was the most important driver of species abundance, followed by shell condition, water temperatures in the coastal Barents Sea in May and June, and sex. These factors, coupled with the range expansion of red king crabs and climate changes in the Barents Sea, provide good explanations for the differences between the 2004–2008 and 2009–2013 fouling communities. Distribution patterns for common taxa on the host reflect larval settlement patterns and/or relationships between the host and associated species. These results expand our knowledge of infestation patterns for the invasive red king crab and provide a reference point for further monitoring. [ABSTRACT FROM AUTHOR]

Oceanographic and ice conditions in the region of Spitsbergen Bank in the Barents Sea were investigated in research cruises of the "Polarsyssel" in 2017–2019. Trajectories of ice drift were constructed using GPS data of the buoys deployed on the floes in the research cruises. The duration of the ice season in the region was analyzed using ice charts. The air temperature and wind velocities were analyzed using the data of meteorological stations on Bear Island and Hopen Island. Fieldwork on drifting ice showed the existence of thick consolidated floes with drafts up to 8 m, which were identified as completely consolidated sea ice ridges. The presence of such floes is dangerous for winter navigation along Spitsbergen Bank. A model of thermodynamic consolidation of ice ridges was formulated to investigate the thermodynamic evolution of ice ridges. The observed air and sea water temperatures were used in the boundary conditions on top and bottom surfaces of sea ice rubble. It was shown that the regular interaction of sea ice rubble with Atlantic and Arctic waters in the region of Spitsbergen Bank leads to almost complete consolidation of the ice rubble with an initial macro-porosity 0.2 for 150 days. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the influence of errors on the accuracy of estimation of absorbed solar energy in the visible spectral range in the water column of the Barents Sea occurring due to the use of various satellite ocean color chlorophyll-retrieval algorithms. The estimates of absorbed energy are based on data obtained during field experiments conducted in various parts of the Barents Sea in June-August 2021, as well as on modeling results. A new regional algorithm for evaluation of chlorophyll concentration in the Barents Sea (B22) is presented as a data source. This algorithm provides more accurate estimates compared to the standard MODIS algorithm under conditions of coccolithophore bloom. Comparing of the results of hydro-optical modeling to the data of shipboard hydro-optical measurements made it possible to validate the obtained data and confirmed the correctness of the selected models. Furthermore, we calculate the parameters of underwater light fields and the absorbed thermal energy in the visible spectral range in the seawater column, showing that differences in the chlorophyll concentration due to the accuracy of satellite bio-optical algorithms (30–50%) have little effect on the vertical distribution of solar energy absorbed in the seawater column. [ABSTRACT FROM AUTHOR]

Sea ice loss and accelerated warming in the Barents Sea have recently been one of the main concerns of climate research. In this study, we investigated the trends and possible relationships between sea surface temperature (SST), sea ice concentration (SIC), and local and large-scale atmospheric parameters over the last 39 years (1982 to 2020). We examined the interannual and long-term spatiotemporal variability of SST and SIC by performing an empirical orthogonal function (EOF) analysis. The SST warming rate from 1982 through 2020 was 0.35 ± 0.04 °C/decade and 0.40 ± 0.04 °C/decade in the ice-covered and ice-free regions, respectively. This climate warming had a significant impact on sea-ice conditions in the Barents Sea, such as a strong decline in the SIC (−6.52 ± 0.78%/decade) and a shortening of the sea-ice season by about −26.1 ± 7.5 days/decade, resulting in a 3.4-month longer summer ice-free period over the last 39 years. On the interannual and longer-term scales, the Barents Sea has shown strong coherent spatiotemporal variability in both SST and SIC. The temporal evolution of SST and SIC are strongly correlated, whereas the Atlantic Multidecadal Oscillation (AMO) influences the spatiotemporal variability of SST and SIC. The highest spatial variability (i.e., the center of action of the first EOF mode) of SST was observed over the region bounded by the northern and southern polar fronts, which are influenced by both warm Atlantic and cold Arctic waters. The largest SIC variability was found over the northeastern Barents Sea and over the Storbanken and Olga Basin. The second EOF mode revealed a dipole structure with out-of-phase variability between the ice-covered and ice-free regions for the SST and between the Svalbard and Novaya Zemlya regions for SIC. In order to investigate the processes that generate these patterns, a correlation analysis was applied to a set of oceanic (SST) and atmospheric parameters (air temperature, zonal, and meridional wind components) and climate indices. This analysis showed that SST and SIC are highly correlated with air temperature and meridional winds and with two climate indices (AMO and East Atlantic Pattern (EAP)) on an interannual time scale. The North Atlantic Oscillation (NAO) only correlated with the second EOF mode of SST on a decadal time scale. [ABSTRACT FROM AUTHOR]

Novaya Zemlya bora is a strong downslope windstorm in the east of the Barents Sea. This paper considers the influence of the Novaya Zemlya bora on the turbulent heat exchange between the atmosphere and the ocean and on processes in the ocean. Another goal of this study is to demonstrate the sensitivity of simulated turbulent fluxes during bora to model coupling between atmosphere, ocean and sea waves. In this regard, a high-resolution numerical simulation of one winter bora episode was carried out using the COAWST (Coupled-Ocean-Atmosphere-Wave-Sediment Transport) modeling system, which includes the atmospheric (WRF-ARW model), oceanic (ROMS model), and sea waves (SWAN model) components. As shown by the simulation results, in the fully coupled experiment, turbulent heat exchange is enhanced in comparison with the uncoupled experiment (by 3% on average over the region). This is due to the atmosphere-sea-waves interaction, and the results are highly sensitive to the choice of roughness parameterization. The influence of the interaction of the atmospheric and oceanic components on turbulent fluxes in this episode is small on average. Bora has a significant impact on the processes in the ocean directly near the coast, forming a strong coastal current and making a decisive contribution to the formation of dense waters. In the open sea, the bora, or rather, the redistribution of the wind and temperature fields caused by the orography of Novaya Zemlya, leads to a decrease in ocean heat content losses due to a decrease in turbulent heat exchange in comparison with the experiment with flat topography. [ABSTRACT FROM AUTHOR]

The invasive red king crab, Paralithodes camtschaticus, has become an abundant and important component in the food web of the coastal Barents Sea and can affect the structure and functioning of the local benthic communities through competition and predation. Although dietary composition and feeding behavior of the crab have been intensively studied, prey selectivity in this species under natural conditions remains poorly defined. For this reason, juvenile red king crabs and benthic samples were collected simultaneously at five coastal sites in Kola Bay to reveal the species composition and structure of feeding habits and the diet of red king crabs. The results of stomach and gut content analyses coupled with calculated Ivlev's indices indicated that 2–5-year-old crabs frequently consumed bivalve mollusks in relative proportions to prey field biomasses. At all sites, juveniles selectively rejected polychaetes. In soft-bottom communities, when the average density of Bivalvia decreased, the crabs showed increased preference for Gastropoda, Crustacea, and Echinodermata. As a result of selective feeding focused on infaunal suspension-feeding mollusks, juvenile red king crabs have altered the structure of benthic communities in the mouth of Kola Bay. Our results may have important implications for evaluating the consequences of the crab introduction and its population management. [ABSTRACT FROM AUTHOR]

Simple Summary: Microbial plankton represent a pivotal component of aquatic ecosystems worldwide. Despite their importance in pelagic ecosystems, microbial assemblages are less studied, in many Arctic regions. The study was concerned with the abundance of marine bacteria and viruses, in relation to a set of environmental variables, after the main productive season. We found a mosaic horizontal distribution of the microbial plankton, while the number of bacteria and viruses decreased with depth. Nutrients and zooplankton carbon were significant drivers of microbial abundance. Bacterioplankton abundance was positively correlated with counts of viruses, indicating close relations between these groups of microbes. Comparisons with previous studies revealed strong seasonal variations in the total abundance of marine bacteria, with the maximum values being in the summer and spring periods, while virioplankton counts were comparable in the autumn and spring–summer seasons. Our study is the first report regarding microbial plankton in the northeastern Barents Sea, in the autumn period, and provides baseline information, expanding current knowledge on the structure of pelagic Arctic ecosystems. In the marine environment, bacteria and viruses play a significant role in carbon fluxes, remineralization processes, and the infection of various organisms. We performed a survey in the northeastern Barents Sea, a region adjacent to the Arctic Ocean, to investigate spatial patterns of microbial plankton, after the main productive period, in October 2020. Two main water masses occurred in the study region—colder Arctic Water and warmer Barents Sea Water, representing transformed Atlantic Water. Multivariate analyses detected patchiness in the horizontal distribution of bacteria and viruses, and their abundances showed no clear association with the water masses. There was an obvious vertical pattern in microbial concentration, with the highest estimates in the upper layers. Surface viral and bacterial abundance varied in a wide range (2.20 × 105–10.7 × 105 cells·mL−1 and 0.86 × 106–14.98 × 106 particles·mL−1, respectively) and were correlated with each other. Bacterioplankton was dominated by small-sized cells (<2 μm, 0.04–0.06 µm3), and the average volume of bacterial cells tended to increase toward the seafloor. The ratio of viral to bacterial abundance (VBR) was 11 ± 1 and did not differ between water masses and depth layers. VBR were higher, compared to summer values, suggesting a strong impact of viruses on bacterioplankton, after the main productive season. Redundancy and correlation analyses showed that inorganic nutrients (nitrate and phosphate) and organic carbon from zooplankton were most responsible for the total variability in the microbial parameters. Water temperature and salinity, also, had a measurable impact, but their influence was lower. Bacterial abundance was lower than in other seasons and regions of the Barents Sea, while viral abundance was comparable, suggesting a stronger viral impact on Arctic marine bacteria in the autumn season. [ABSTRACT FROM AUTHOR]

Over the recent few decades, due to climate warming and the continuing exploration of Arctic seas' mineral resources, the scientific interest in contamination problems has deepened significantly. In this study, for the first time, we characterize the distribution features of 47 elements (major and trace elements, including heavy metals, metalloid As, and Cs-137 technogenic radionuclide) in surface bottom sediments from some areas of the Barents, Kara, Laptev, and East-Siberian Seas. The lithogenic material was the main factor that controlled variability in many elements (Be, Al, Ti, Cr, Ga, Rb, Sr, Y, Zr, Nb, Ba, REE, Pb, Th, U, W, and Cs). Among the hydrogenic processes, the formation of Fe and Mn oxyhydroxides has the greatest impact on the Mn, Fe, Co, Ni, Cu, Ge, and Mo, and insignificantly V and Sb, variability in sediments. These, along with minor to moderate values of enrichment factor (EF) for most elements, allowed us to conclude that the observed element distribution is related to predominantly natural processes of thermal abrasion, river-run, and atmospheric input. The exception is As, which exhibited the elevated EF (up to 20) in the western and central Kara Sea, as well as in the Vilkitsky Strait. Since no significant relationship between As and Fe andMn oxyhydroxides distribution was found, we may assume primarily an anthropogenic source of As, related to the peat and/or coal combustion. According to the criteria of Ecological Risks assessment, all the examined areas have a low degree of risk. Data on the specific activity of Cs-137 correspond to the background average values characteristic for these regions. The highest levels of Cs-137 concentration (Bq/kg) were detected in the sediments of the Ob and Yenisei Rivers' estuaries. [ABSTRACT FROM AUTHOR]

Hydrocarbon prospectivity in the Greater Barents Sea remains enigmatic as gas discoveries have dominated over oil in the past three decades. Numerous hydrocarbon-related fluid flow anomalies in the area indicate leakage and redistribution of petroleum in the subsurface. Many questions remain unanswered regarding the geological driving factors for leakage from the reservoirs and the response of deep petroleum reservoirs to the Cenozoic exhumation and the Pliocene-Pleistocene glaciations. Based on 2D and 3D seismic data interpretation, we constructed a basin-scale regional 3D petroleum systems model for the Hammerfest Basin (1 km × 1 km grid spacing). A higher resolution model (200 m × 200 m grid spacing) for the Snøhvit and Albatross fields was then nested in the regional model to further our understanding of the subsurface development over geological time. We tested the sensitivity of the modeled petroleum leakage by including and varying fault properties as a function of burial and erosion, namely fault capillary entry pressures and permeability during glacial cycles. In this study, we find that the greatest mass lost from the Jurassic reservoirs occurs during ice unloading, which accounts for a 60-80% reduction of initial accumulated mass in the reservoirs. Subsequent leakage events show a stepwise decrease of 7-25% of the remaining mass from the reservoirs. The latest episode of hydrocarbon leakage occurred following the Last Glacial Maximum (LGM) when differential loading of Quaternary strata resulted in reservoir tilt and spill. The first modeled hydrocarbon leakage event coincides with a major fluid venting episode at the time of a major Upper Regional angular Unconformity (URU, ∼0.8 Ma), evidenced by an abundance of pockmarks at this stratigraphic interval. Our modelling results show that leakage along the faults bounding the reservoir is the dominant mechanism for hydrocarbon leakage and is in agreement with observed shallow gas leakage indicators of gas chimneys, pockmarks and fluid escape pipes. We propose a conceptual model where leaked thermogenic gases from the reservoir were also locked in gas hydrate deposits beneath the base of the glacier during glaciations of the Hammerfest Basin and decomposed rapidly during subsequent deglaciation, forming pockmarks and fluid escape pipes. This is the first study to our knowledge to integrate petroleum systems modelling with seismic mapping of hydrocarbon leakage indicators for a holistic numerical model of the subsurface geology, thus closing the gap between the seismic mapping of fluid flow events and the geological history of the area. [ABSTRACT FROM AUTHOR]

The presence of sea-ice leads represents a key feature of the Arctic sea ice cover. Leads promote the flux of sensible and latent heat from the ocean to the cold winter atmosphere and are thereby crucial for air-sea-ice-ocean interactions. We here apply a binary segmentation procedure to identify leads from MODIS thermal infrared imagery on a daily time scale. The method separates identified leads into two uncertainty categories, with the high uncertainty being attributed to artifacts that arise from warm signatures of unrecognized clouds. Based on the obtained lead detections, we compute quasi-daily pan-Arctic lead maps for the months of January to April, 2003-2015. Our results highlight the marginal ice zone in the Fram Strait and Barents Sea as the primary region for lead activity. The spatial distribution of the average pan-Arctic lead frequencies reveals, moreover, distinct patterns of predominant fracture zones in the Beaufort Sea and along the shelf-breaks, mainly in the Siberian sector of the Arctic Ocean as well as the well-known polynya and fast-ice locations. Additionally, a substantial inter-annual variability of lead occurrences in the Arctic is indicated. [ABSTRACT FROM AUTHOR]

In this work we examined morphological variation at different levels to study performance and population structuring of the blue mussel Mytilus edulis. Our objectives were: (i) to develop an integrated technique for analyzing morphological variation in blue mussels and, based on this technique; (ii) to perform a morphometric description of mussels from the northern part of their range; and (iii) to verify the hypothesis that populations at the outer range of their distribution have reduced performance due to harsh climatic conditions. Means, directional asymmetry (i.e., systematic differences between left and right structures), fluctuating asymmetry (random deviations from perfect symmetry, a measure of developmental instability), factorial variation (difference between total variance and variance of fluctuating asymmetry, an indirect index of genotypic variation), and measurement error were examined for 14 bilateral characters of muscle scars on mussel shells. Also, we analyzed one non-bilateral character. For the first time directional asymmetry-approaching 13% of the right:left ratio-was described in blue mussels. Measurement error, often ignored in morphometric studies, contributed 26% of total variance. Accurately addressing these methodical challenges is key to further and improved ecological interpretations. Morphological differences were found between (i) samples from estuarine areas in the White and Pechora Seas and (ii) samples from Barents Sea areas with oceanic salinity. Samples from the first group exhibited lower fluctuating asymmetry, indicating higher developmental stability likely due to better feeding conditions and lower factorial variation, which may result from lower genotypic variation. Absence of correlation between fluctuating asymmetry and temperature suggests that low temperatures in the northern border of their range do not degrade the performance of adult blue mussels in this region. [ABSTRACT FROM AUTHOR]

Simple Summary: Bryozoans are colonial organisms that are usually found attached to solid substrata. They are known to be common components of benthic communities from the littoral zone to deep-sea areas. Despite the long history of bryozoan research in the Barents Sea, intertidal communities of this group are less studied than those at open water sites. This is particularly true for the assessment of the role of environmental factors in diversity and biomass fluctuations of Arctic bryozoan assemblages. We collected bryozoans at two adjoining coastal sites in the southern Barents Sea and detected range extension of one boreal species, which reflects a warming trend and borealization of the benthic fauna in the region. In general, the total bryozoan biomass and diversity were lower than in deep-water sites of the sea. Salinity and temperature were found to be the main predictors of bryozoan species richness and biomass, respectively, with more diverse and abundant assemblages occupying habitats with higher salinity and lower temperature. Our findings are in accordance with a general opinion that benthic communities of the coastal Barents Sea are mainly controlled by temperature regime fluctuations and freshwater runoffs. There is a lack of knowledge regarding the modern status of intertidal bryozoan communities in the coastal Barents Sea. Here, we studied species composition, richness, and biomass of bryozoans in Yarnyshnaya and Dalnezelenetskaya Bays, both located in the eastern part of the Kola Peninsula (Barents Sea), in summer. Species composition and biodiversity were consistent with previous research but the record of the ctenostome bryozoan Walkeriauva is the first for the region indicating eastward range expansion of this species associated with climate forcing in the Arctic. Mean biomass was relatively low accounting for 2.25 ± 0.95 g·m−2. The most common species were Eucratea loricata, Harmeria scutulata, Crisia eburnea, and Cribrilina cryptooecium averaging 96% of the total biomass. Cluster analysis delineated two distinct groups of stations, one with true marine conditions and another with brackish water conditions. Redundancy analysis revealed that bryozoan diversity was strongly associated with salinity fluctuations being extremely low at brackish water sites. In contrast, water temperature was found to be a significant contributor to biomass with the lowest values found at warmer waters probably owing to the predominance of Boreo-Arctic species which prefer lower-temperatures. Other hydrological variables (dissolved organic matter, silicates, and oxygen) were consistent with usual summer values and had no significant effects on the bryozoan assemblages. Our study provides a reference point for further biodiversity studies in changing marine ecosystems of the Arctic region. [ABSTRACT FROM AUTHOR]

Simple Summary: In vertebrates, thyroid hormones, triiodothyronine, and thyroxine play a pivotal role in regulating development, metamorphosis, and metabolism. Recently, the presence of endogenous thyroid hormone signaling has also been reported in invertebrates. We assayed thyroid hormone profiles in the red king crab, an iconic commercially important species, which was introduced into the Barents Sea in the 1960s and now is supporting a large-scale profitable fishery. Both thyroid hormones were detected in the crab hemolymph. Their levels fluctuated significantly depending on the maturity status of the crabs and sampling season. These findings confirm that thyroid hormones are involved in the specific physiological processes of red king crabs and may be used in aquaculture. Only a few studies have reported the presence and levels of thyroid hormones in invertebrates. At the same time, the administration of these hormones has been shown to be a profitable method for inducing growth in crustaceans. Knowledge of thyroid hormone concentrations is required to involve this approach in crustacean aquaculture. For this reason, we examined hemolymph samples of the invasive red king crab Paralithodes camtschaticus from the Barents Sea population for the levels of triiodothyronine (T3) and thyroxine (T4). Radioimmunoassays indicated that T3 ranged from 0.26 to 1.55 μg dL–1, whereas T4 varied from 52 to 203 μg dL–1. Adult crabs demonstrated higher levels of T3 than juveniles, while juvenile crabs had higher levels of T4 in comparison to larger conspecifics. The thyroxine levels were consistent throughout the study period. In contrast, significant seasonal variations were found for T3. In immature crabs, the maximum concentration was found in October, whereas in adult crabs, the highest level of T3 was registered in August. Most likely, these results are explained by changes in physiological conditions of the crabs associated with their molting calendar and migration activity. Our data may have important implications for aquaculture of Paralithodes camtschaticus in the Barents Sea. [ABSTRACT FROM AUTHOR]

Simple Summary: Arctic coastal waters have been strongly influenced by climatic fluctuations during the past decades. Recent studies reported clear warming processes in the Barents Sea and adjacent waters. Plankton assemblages are good indicators of environmental changes, and their composition and production affect all components of pelagic ecosystems. Most of data on the zooplankton in Arctic seas were obtained during summer seasons, and little is known about zooplankton communities in other seasons. Spring is one of the crucial periods in the Arctic marine environment, as primary production may reach the annual maximum. To investigate a spring pattern of Arctic mesozooplankton, we performed a study in the eastern Barents Sea. This research is the first report on the spring coastal zooplankton near the Novaya Zemlya Archipelago. We revealed high diversity and abundance of zooplankton taxa. Environmental variability had a significant impact on the mesozooplankton assemblages, with geographical location and phytoplankton density being the most important. Our data may be useful for future investigations dealing with Arctic plankton communities during the era of global climatic changes. Mesozooplankton play an important role in Arctic shelf ecosystems as a trophic link and a key food source for many larval fish species. The distribution of mesozooplankton in the eastern Barents Sea was studied along a 500 nautical mile-long transect in May 2016 during the spring bloom. Mesozooplankton were sampled using a Juday net hauled from the surface to the bottom at 12 stations. We found good correspondence between the distribution of water masses and mesozooplankton assemblages. Mesozooplankton abundance (mean 73·103 individuals m−2) in Novaya Zemlya coastal water was dominated by Copepoda ova and nauplii, Thyssanoessa spp. nauplii and Oithona similis. Parasagitta elegans and Calanus finmarchicus comprised most of the total mesozooplankton biomass (mean 0.9 g dry mass m−2) in that water mass. A second assemblage (mean abundance 171·103 individuals m−2) was associated with the colder Barents Sea water, with Oithona similis, Copepoda nauplii, Fritillaria borealis and Cirripedia nauplii being the most numerous. In that water mass, C. finmarchicus, Metridia longa, Cirripedia nauplii and Calanus glacialis contributed most to the total biomass (mean 3 g dry mass m−2). The dominance of young stages of Copepoda and a high proportion of meroplankton were typical of spring mesozooplankton assemblages. The spatial distribution of mesozooplankton abundance and biomass was strongly correlated with latitude, longitude and chlorophyll a concentration, which together explained 10% of the total variance in mesozooplankton density. The present investigation is a baseline study for the assessment of the spring mesozooplankton assemblage in the eastern Barents Sea, and for an evaluation of the possible impact of future environmental changes on the Arctic shelf marine ecosystem. [ABSTRACT FROM AUTHOR]

In response to declining sea ice cover, human activity in the Arctic is increasing, with access to the Arctic Ocean becoming more important for socio-economic reasons. Accurate knowledge of sea ice conditions is therefore becoming increasingly important for reducing the risk and operational cost of human activities in the Arctic. Satellite-based sea ice charting is routinely used for tactical ice management, but the marine sector does not yet make optimal use of sea ice thickness (SIT) or sea ice concentration (SIC) forecasts on weekly timescales. This is because forecasts have not achieved sufficient accuracy, verification and resolution to be used in situations where maritime safety is paramount, and assessing the suitability of forecasts can be difficult because they are often not available in the appropriate format. In this paper, existing SIT forecasts currently available on the Copernicus Marine Service (CMS) or elsewhere in the public domain are evaluated for the first time. These include the seven-day forecasts from the UK Met Office, MET Norway, the Nansen Environmental and Remote Sensing Center (NERSC) and the European Centre for Medium-Range Weather Forecasts (ECMWF). Their forecast skills were assessed against unique in situ data from five moorings deployed between 2016 and 2019 by the Barents Sea Metocean and Ice Network (BASMIN) and Barents Sea Exploration Collaboration (BaSEC) Joint Industry Projects. Assessing these models highlights the importance of data assimilation in short-term forecasting of SIT and suggests that improved assimilation of sea ice data could increase the utility of forecasts for navigational purposes. This study also demonstrates that forecasts can achieve similar or improved correlation with observations when compared to a persistence model at a lead time of seven days, providing evidence that, when used in conjunction with sea ice charts, SIT forecasts could provide valuable information on future sea ice conditions. [ABSTRACT FROM AUTHOR]

This work summarizes ice algal studies, presented as biomass and species temporal and spatial distribution, during 11 cruises conducted between 1986 and 2012. The majority of the biomass was found as loosely attached sub-ice algal layers, and sampling required diving. A maximum of 40 mg chlorophyll m−2 and 15.4 × 109 cells m−2 was measured in May. The species diversity was separated in zones based on ice thickness, with the highest biodiversity in the medium-thick ice of 30–80 cm. Nitzschia frigida was the most common species. There was a significant positive relationship between the dominance of this species and ice thickness, and it dominated completely in thick ice. Other common species, such as N. promare and Fossulaphycus arcticus reacted oppositely, by becoming less dominant in thick ice, but the positive correlation between total cell numbers and number of these three species indicated that they would most likely dominate in most populations. Melosira arctica was found several times below medium-thick annual ice. Algae occurred from top to bottom in the ice floes and in infiltration layers, but in very low numbers inside the ice. The bipolar dinoflagellates Polarella glacialis inhabited the ice, both as vegetative cells and cysts. The algal layers detached from the ice and sank in late spring when melting started. The cells in the sediments form an important food source for benthic animals throughout the year. Fjord populations survive the winter on the bottom and probably form next year's ice algal inoculum. A few 'over-summer' populations found in sheltered locations might provide supplementary food for ice amphipods in late summer. The future faith of the ice flora is discussed in view of a warmer climate, with increased melting of the Arctic ice cover. [ABSTRACT FROM AUTHOR]

Crabs are important ecosystem engineers in marine habitats worldwide. Based on long-term data, we analyzed the species composition and infestation indices of epibionts and symbionts colonizing the great spider crab, Hyas araneus, and two lithodid crabs—the northern stone crab, Lithodes maja, and the red king crab, Paralithodes camtschaticus—in the coastal zone of the Barents Sea. The epibiotic communities found on great spider crabs were closer to northern stone crabs (33%) compared to red king crabs (25%). The prevalence of mobile symbionts (amphipods, Ischyrocerus, and polychaetes, Harmothoe) and common epibionts, such as barnacles and hydrozoans, was low on great spider crabs and high on the body and in the gills of lithodid crabs. Epiphytes were abundant on great spider crabs but not present on both species of lithodid crabs. Egg symbionts found on H. araneus and P. camtschaticus do not affect their local populations. Differences in the fouling communities found on the three crab species are associated with host size range, surface properties of their carapaces, and behavior patterns. [ABSTRACT FROM AUTHOR]

Effects of the sea-ice edge and the Polar Frontal Zone on the distribution of chlorophyll-a levels in the pelagic were investigated during multi-year observations in insufficiently studied and rarely navigable regions of the Barents Sea. Samples were collected at 52 sampling stations combined into 11 oceanographic transects over a Barents Sea water area north of the latitude 75° N during spring 2016, 2018, and 2019. The species composition, abundance and biomass of the phytoplankton community, chlorophyll-a concentrations, hydrological and hydrochemical parameters were analyzed. The annual phytoplankton evolution phase, defined as an early-spring one, was determined throughout the transects. The species composition of the phytoplankton community and low chlorophyll-a levels suggested no phytoplankton blooming in April 2016 and 2019. Not yet started sea-ice melting prevented sympagic (sea-ice-associated) algae from being released into the seawater. In May 2018, ice melting began in the eastern Barents Sea and elevated chlorophyll-a levels were recorded near the ice edge. Chlorophyll-a concentrations substantially differed in waters of different genesis, especially in areas influenced by the Polar Front. The Polar Front separated the more productive Arctic waters with a chlorophyll-a concentration of 1–5 mg/m3 on average from the Atlantic waters where the chlorophyll-a content was an order of magnitude lower. [ABSTRACT FROM AUTHOR]

In spring 2016, the thermohaline characteristics of water masses and the distribution of chlorophyll-a concentration in the pelagic zone of the eastern part of the Barents Sea were studied. For the first time, in the conditions of an abnormally warm year and the absence of ice cover, a complex of hydrobiological works was carried out on a section crossing the Barents Sea from south to north along the western coast of the Novaya Zemlya archipelago. High concentrations of chlorophyll-a > 1 ˂ 6 mg/m3 at all stations of the transect indicate a stage of spring bloom in the successional cycle of microalgae. Significant differences in the content of chlorophyll-a in waters of various origins were revealed. The highest concentrations of chlorophyll-a corresponded to Arctic surface water (5.56 mg/m3). Slightly lower values were observed in the transformed Atlantic waters of the Novozemelskoe and Kolguevo–Pechorskoe currents (3.53 ± 0.97–3.71 ± 1.04 mg/m3), and the lowest was in the Barents waters (1.24 ± 0.84–1.45 ± 1.13 mg/m3). [ABSTRACT FROM AUTHOR]

The results of the study of hydrocarbons (HCs): aliphatic (AHCs) and polycyclic aromatic hydrocarbons (PAHs) in bottom sediments (2019 and 2020, cruises 75 and 80 of the R/V Akademik Mstislav Keldysh) in the Norwegian-Barents Sea basin: Mohns Ridge, shelf Svalbard archipelago, Sturfiord, Medvezhinsky trench, central part of the Barents Sea, Novaya Zemlya shelf, Franz Victoria trough are presented. It has been established that the organo-geochemical background of the Holocene sediments was formed due to the flow of sedimentary material in the coastal regions of the Barents Sea on shipping routes. The anthropogenic input of HCs into bottom sediments leads to an increase in their content in the composition of Corg (in the sandy sediments of the Kaninsky Bank at an AHC concentration up to 64 μg/g, when its proportion in the composition of Corg reaches 11.7%). The endogenous influence on the of the Svalbard archipelago shelf in Sturfiord and in the Medvezhinsky Trench determines the specificity of local anomalies in the content and composition of HCs. This is reflected in the absence of a correlation between HCs and the grain size composition of sediments and Corg content, as well as a change in hydrocarbon molecular markers. At the same time, the sedimentary section is enriched in light alkanes and naphthalene's that may be due to emission during point discharge of gas fluid from sedimentary rocks of the lower stratigraphic horizons and/or sipping migration. [ABSTRACT FROM AUTHOR]

Frenulate siboglinids are a characteristic component of communities living in various reducing environments, including sites with hydrocarbon seeps. High concentrations of hydrocarbons in the sediments of the Arctic basin seas, including the Barents Sea, suggest the presence of a rich siboglinid fauna there. This reflects the fact that microbiological oxidation of methane occurs under reducing conditions, generating high concentrations of hydrogen sulfide in the sediment. This hydrogen sulfide acts as an energy source for the sulfide-oxidizing symbionts of siboglinids. Here we report on the findings of the frenulate siboglinid species Nereilinum murmanicum made between 1993 and 2020 in the Barents Sea. These data significantly expand the range of this species and yield new information on its habitat distribution. The depth range of N. murmanicum was 75–375 m. The species was most abundant from 200 to 350 m and was associated with temperatures below 3 °C and salinities from 34.42 to 35.07. Most of the findings (43 locations or 74%) fall on areas highly promising for oil and gas production. Twenty-eight locations (48%) are associated with areas of known oil deposits, 22 locations (37%) with explored areas of gas hydrate deposits. N. murmanicum was also found near the largest gas fields in the Barents Sea, namely Shtokman, Ludlovskoye and Ledovoye. [ABSTRACT FROM AUTHOR]

A combination of physicochemical and radiotracer analysis, high-throughput sequencing of the 16S rRNA, and particulate methane monooxygenase subunit A (pmoA) genes was used to link a microbial community profile with methane, sulfur, and nitrogen cycling processes. The objects of study were surface sediments sampled at five stations in the northern part of the Barents Sea. The methane content in the upper layers (0–5 cm) ranged from 0.2 to 2.4 µM and increased with depth (16–19 cm) to 9.5 µM. The rate of methane oxidation in the oxic upper layers varied from 2 to 23 nmol CH4 L−1 day−1 and decreased to 0.3 nmol L−1 day−1 in the anoxic zone at a depth of 16–19 cm. Sulfate reduction rates were much higher, from 0.3 to 2.8 µmol L−1 day−1. In the surface sediments, ammonia-oxidizing Nitrosopumilaceae were abundant; the subsequent oxidation of nitrite to nitrate can be carried out by Nitrospira sp. Aerobic methane oxidation could be performed by uncultured deep-sea cluster 3 of gamma-proteobacterial methanotrophs. Undetectable low levels of methanogenesis were consistent with a near complete absence of methanogens. Anaerobic methane oxidation in the deeper sediments was likely performed by ANME-2a-2b and ANME-2c archaea in consortium with sulfate-reducing Desulfobacterota. Sulfide can be oxidized by nitrate-reducing Sulfurovum sp. Thus, the sulfur cycle was linked with the anaerobic oxidation of methane and the nitrogen cycle, which included the oxidation of ammonium to nitrate in the oxic zone and denitrification coupled to the oxidation of sulfide in the deeper sediments. Methane concentrations and rates of microbial biogeochemical processes in sediments in the northern part of the Barents Sea were noticeably higher than in oligotrophic areas of the Arctic Ocean, indicating that an increase in methane concentration significantly activates microbial processes. [ABSTRACT FROM AUTHOR]

Gas chimneys are one of the most intriguing manifestations of the focused fluid flows in sedimentary basins. To predict natural and human-induced fluid leakage, it is essential to understand the mechanism of how fluid flow localizes into conductive chimneys and the chimney dynamics. This work predicts conditions and parameters for chimney formation in two fields in the SW Barents Sea, the Tornerose field and the Snøhvit field in the Hammerfest Basin. The work is based on two types of models, basin modeling and hydro-mechanical modeling of chimney formation. Multi-layer basin models were used to produce the initial conditions for the hydro-mechanical modeling of the relatively fast chimneys propagation process. Using hydro-mechanical models, we determined the thermal, structural, and petrophysical features of the gas chimney formation for the Tornerose field and the Snøhvit field. Our hydro-mechanical model treats the propagation of chimneys through lithological boundaries with strong contrasts. The model reproduces chimneys identified by seismic imaging without pre-defining their locations or geometry. The chimney locations were determined by the steepness of the interface between the reservoir and the caprock, the reservoir thickness, and the compaction length of the strata. We demonstrate that chimneys are highly-permeable leakage pathways. The width and propagation speed of a single chimney strongly depends on the viscosity and permeability of the rock. For the chimneys of the Snøhvit field, the predicted time of formation is about 13 to 40 years for an about 2 km high chimney. [ABSTRACT FROM AUTHOR]

Simple Summary: Well-known sex hormones, testosterone and 17β-estradiol, play a crucial role in the reproduction of vertebrates. Biochemical assays have detected these substances in a few crustaceans, and it has been hypothesized that these hormones are involved in the regulation of crustacean reproduction. Red king crab is a large commercially important species harvested both in their native areas (North Pacific) and in the area of its introduction (Barents Sea). The presence of 17β-estradiol and testosterone and fluctuations of their concentrations in relation to different factors have not yet been investigated. For this reason, we provided a pilot study to reveal the levels of sex hormones in hemolymph of red king crabs captured in the coastal Barents Sea. These hormones were detected in the crabs and we compared our data with previously published data involving a wide range of crustaceans. We found seasonal variations in the level of testosterone with the maximum in the spawning period. Our data expand the current knowledge about the red king crab physiology and may be used for the development of its aquaculture. The presence of vertebrate-related steroid sex hormones has been reported in both freshwater and marine crustaceans. However, despite the commercial importance of king crabs, many aspects of their endocrinology are still unknown. For this reason, we examined hemolymph samples of the red king crab Paralithodes camtschaticus from the Barents Sea population for the presence of testosterone and 17β-estradiol using radioimmunoassay. The mean testosterone concentration was 0.46 ± 0.04 (range 0.08–1.39) ng mL–1, whereas the mean 17β-estradiol concentration was 1248.9 ± 91.4 (range 217.7–4100.1) pg mL–1. In general, the levels of 17β-estradiol and testosterone in red king crabs were higher than reported for the hemolymph of amphipods, crabs, and shrimps from warm and temperate waters, probably because the king crabs analyzed were larger and heavier than the other crustaceans. The concentrations of sex steroids did not differ significantly between males and females and between immature and mature red king crabs. Seasonal variations in the level of testosterone with the maximum value in the spawning period (May) indicate a potential role of the sex hormones in the maturation and reproduction processes of red king crab. Taking into account the slow growth rate in P. camtschaticus, our data could be useful not only for further physiological studies but also for the development of reliable techniques for red king crab aquaculture. [ABSTRACT FROM AUTHOR]

A decade-long pronounced increase in temperatures in the Arctic, especially in the Barents Sea region, resulted in a global warming hotspot over Svalbard. Associated changes in the cryosphere are the consequence and lead to a demand for monitoring of the glacier changes. This study uses spaceborne laser altimetry data from the ICESat and ICESat-2 missions to obtain ice elevation and mass change rates between 2003–2008 and 2019. Elevation changes are derived at orbit crossover locations throughout the study area, and regional volume and mass changes are estimated using a hypsometric approach. A Svalbard-wide annual elevation change rate of −0.30 ± 0.15 m yr−1 was found, which corresponds to a mass loss rate of −12.40 ± 4.28 Gt yr−1. Compared to the ICESat period (2003–2009), thinning has increased over most regions, including the highest negative rates along the west coast and areas bordering the Barents Sea. The overall negative regime is expected to be linked to Arctic warming in the last decades and associated changes in glacier climatic mass balance. Further, observed increased thinning rates and pronounced changes at the eastern side of Svalbard since the ICESat period are found to correlate with atmospheric and oceanic warming in the respective regions. [ABSTRACT FROM AUTHOR]