Fatty Acids in the Eggs of Red King Crabs from the Barents Sea.

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.

Amino Acid Composition in Different Tissues of Iceland Scallop from the Barents Sea.

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.

Marine copepod assemblages in the Arctic: The effect of frontal zones on biomass and productivity.

The Barents Sea, as the largest Arctic shelf region with high productivity, supports vital commercial fisheries. The region's ecosystem is significantly impacted by both warm Atlantic Water (AW) and cold Arctic Water (ARW), resulting in frontal zones that delineate differing water masses. Zooplankton populations serve as the primary link between primary producers and higher trophic levels. To evaluate the potential influence of frontal zones on copepods, we conducted a summer survey focusing on sites where diverse water masses interacted. Our findings revealed that species richness, diversity, biomass, and daily production of common copepods were highest in the Polar Front, separating AW and ARW, as well as in the eastern frontal zones (Barents Sea Water and Novaya Zemlya Coastal Water). Herbivorous copepods, such as Calanus spp. and Pseudocalanus spp., dominated in terms of total copepod biomass and production, whereas the small omnivore Oithona similis prevailed by abundance. Multivariate analysis demonstrated a strong correspondence between frontal zones and copepod assemblages. The primary factors explaining spatial variations in copepod biomass and production included the geographic positions of sampling stations, depth, and chlorophyll a concentration. Our research underscores the significance of oceanographic fronts as zones of critical importance for overall pelagic productivity in Arctic regions.

Local variability of Arctic mesozooplankton biomass and production: A case summer study.

The Barents Sea is a highly productive ecosystem within the Arctic Ocean. The overall biological productivity in this region relies heavily on the secondary mesozooplankton production (MZP). Previous research has primarily focused on mesozooplankton abundance (MZA) and biomass (MZB), lacking a comprehensive analysis of the environmental factors that influence MZP in the Arctic marine environment. The primary objective of this study was to examine the key factors responsible for the spatial variability in the community structure and MZP during the summer season. Data were collected from 52 stations in the central Barents Sea, specifically during post-bloom conditions in 2015. Through cluster analysis, two distinct groups of stations were identified, differing in terms of mesozooplankton taxa abundance. Copepods were found to dominate the mesozooplankton assemblages, comprising 89% of total MZA, 83% of MZB, and 68% of MZP. The biomass stocks in the study area varied from 8 to 102 mg dry mass (DM) m-3, with an average of 44 mg DM m-3. MZP rates ranged from 0.34 to 2.33 mg DM m-3 day-1, with an average of 1.16 mg DM m-3 day-1. The highest MZB and MZP values were observed at frontal zones that separated relatively warm and cold waters. Through redundancy analysis, it was determined that the primary environmental factors affected the distribution of mesozooplankton were longitude, latitude, and sampling depth. Temperature, salinity, and chlorophyll a concentration were found to have a less significant impact. These findings emphasize the importance of oceanographic conditions as the main predictors of mesozooplankton distribution during the summer season in the Arctic marine environment. This study highlights the essential role of environmental forcing in determining the productivity of Arctic marine zooplankton. Given the ongoing climatic changes, the results of this report can serve as a valuable tool for monitoring pelagic ecosystems in the Arctic.

Marine Plankton during the Polar Night: Environmental Predictors of Spatial Variability.

We studied the spatial patterns of the planktonic ecosystems at two Arctic sites strongly affected by Atlantic Inflow (FS, the Fram Strait; and BS, the Barents Sea). A high degree of similarity in the bacterial abundance (mean: 3.1 × 105 cells mL-1 in FS vs. 3.5 × 105 cells mL-1 in BS) was found, while other plankton characteristics were different. Bacterial biomass reached a maximum in BS (3.2-7.9 mg C m-3), while viral abundances tended to be higher in FS (2.0-5.7 × 106 particles mL-1). Larger bacterial cells were found in BS, suggesting the presence of different bacterial populations at both locations. The virus-to-bacteria ratio was significantly higher in FS than in BS (13.5 vs. 4.7). Chlorophyll a concentration was extremely low (<0.25 mg m-3). The highest zooplankton abundance was in the surface layer (919 individuals m-3 in FS vs. 602 ind. m-3 in BS). Zooplankton biomass strongly varied (1-39 mg C m-3), with the maximum in BS. High proportions of boreal taxa in the total zooplankton abundance indicate the Atlantification of pelagic ecosystems in the Arctic. Plankton indicators are correlated with temperature, salinity, and sampling depth. Strong intercorrelations were found between major plankton groups, suggesting tight links in the studied plankton ecosystems.

Fatty Acid Composition of Northern Pike from an Arctic River (Northeastern Siberia, Russia).

We assayed the fatty acid composition of muscles of the northern pike Esox lucius Linnaeus, 1758 inhabiting the Gyda River, Siberia, Russia using gas-liquid chromatography. Of 43 fatty acids identified in the pike samples, 23 fatty acids accounted for 99.3% of the total content. The most abundant saturated fatty acids (SFA, 31.6%) were palmitic (C16:0, 20.0%) and stearic (C18:0, 7.3%) acids. Among monounsaturated fatty acids (MUFA, 15.1%), oleic acid (C18:1n9, 10.2%) and palmitoleic acid (C16:1, 4.1%) demonstrated the highest levels. The most represented polyunsaturated fatty acids (PUFA, 53.3%) were arachidonic acid (C20:4n-6, 7.6%), eicosapentaenoic acid (EPA, C20:5n-3, 7.3%), and docosahexaenoic acid (DHA, C22:6n-3, 26.3%). The fatty acid profile of specimens from the Gyda River was different in comparison to profiles found in other pike populations, most likely due to different diets. Pike flesh has good nutrition quality in terms of a low n-6/n-3 ratio (0.36), low atherogenic (0.39), and thrombogenic (0.22) indices, and a high ratio of hypocholesterolemic to hypercholesterolemic fatty acids (2.83), and this species can be recommended as a replacement or alternative to other fish sources in traditional diets.

Fatty Acid Profiles in the Gonads of Red King Crab (Paralithodes camtschaticus) from the Barents Sea.

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.

Effects of Climate Change on Chlorophyll a in the Barents Sea: A Long-Term Assessment.

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.

Winter Epibiotic Community of the Red King Crab Paralithodes camtschaticus in Sayda Bay (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.

Fatty Acid Content of Four Salmonid Fish Consumed by Indigenous Peoples from the Yamal-Nenets Autonomous Okrug (Northwestern Siberia, Russia).

We assayed fatty acids in the flesh of Arctic cisco Coregonus autumnalis (adult and juvenile), least cisco Coregonus sardinella, muksun Coregonus muksun, and Arctic charr Salvelinus alpinus inhabiting water bodies of the Gydan Peninsula, Siberia, Russia. The highest concentrations of total and polyunsaturated fatty acids (PUFAs) were found in Arctic charr (27.8 and 9.5 mg g-1) and adult Arctic cisco (20.2 and 7.6 mg g-1), while the lowest concentrations occurred in juvenile Arctic cisco (7.5 and 3.6 mg g-1). Multivariate analyses divided all studied fish into five distinct groups with the highest similarity between least cisco and muksun and the highest dissimilarity between juvenile Arctic cisco and Arctic charr. Coregonid fish from the study area had a higher content of docosahexaenoic and eicosapentaenoic acids than their conspecifics from subarctic and temperate habitats. The flesh of the studied fish is a source of a healthy diet for humans. Taking into account that all the studied fish are components of the traditional diet of indigenous peoples in northwestern Siberia, our data may be useful not only for local consumers and anglers but also for stakeholders focused on food policy and food security in the area.

Pelagic Bacteria and Viruses in a High Arctic Region: Environmental Control in the Autumn Period.

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 region­colder 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.

Coastal Mesozooplankton Assemblages during Spring Bloom in the Eastern Barents Sea.

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.

Thyroid Hormones in Hemolymph of Red King Crabs from the Barents Sea.

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.

Summer-fall macrozooplankton assemblages in a large Arctic estuarine zone (south-eastern Barents Sea): Environmental drivers of spatial distribution.

Macrozooplankton assemblages were studied during the summer and fall of 2012 in the Pechora Sea, a large coastal region of the south-eastern Barents Sea strongly affected by discharges of freshwater. Sampling was performed at 23 stations with 550-µm mesh IKS-80 nets. We focused on macrozooplankton and large (>1.5 mm) non-copepod zooplankton (larvae of benthic animals and medusae). A combination of multivariate cluster analysis, diversity indices and canonical correspondence analysis was used to relate the spatio-temporal patterns of the zooplankton assemblages to environmental factors. Summer macrozooplankton density varied from 3 to 928 ind. m-3, averaging 131 ± 49 ind. m-3, with medusae being the most numerous (mean ± SE: 67.9 ± 7.8% of the total abundance). The total macrozooplankton biomass ranged from 0.3 to 516 mg dry mass (DM) m-3 with a mean value of 28 ± 25 mgDM m-3. There was a clear decline in the total macrozooplankton abundance (1.1-6.0, 4.4 ± 1.6 ind. m-3) and biomass (0.4-2.7, 1.2 ± 0.7 mgDM m-3) in fall when only two taxa (Parasagitta elegans and Mertensia ovum) were identified. Cluster analysis revealed three groups of stations in summer. The clusters were similar in terms of the abundance in common taxa but differed by the total density, biomass and diversity. We found that the offshore zone was dominated by the euphausiids Thysanoessa spp. and the chaetognaths Parasagitta elegans while the coastal area was characterized by high density of hydromedusae and larvae of bottom animals (Hyas spp., Pagurus spp.). There was a significant decline in the total macrozooplankton abundance and biomass from summer to fall. Canonical correspondence analysis showed that during the summer and fall of 2012, 68% of macrozooplankton variability was explained by environmental factors with water temperature and longitude being the most important. The distribution of macrozooplankton taxa was also related to local circulation patterns and possibly to mesozooplankton as potential prey for carnivorous taxa. Our data may be useful for future monitoring in the coastal Arctic estuarine regions.

Sex Hormones in Hemolymph of Red King Crabs from the Barents Sea.

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 17ß-estradiol using radioimmunoassay. The mean testosterone concentration was 0.46 ± 0.04 (range 0.08-1.39) ng mL-1, whereas the mean 17ß-estradiol concentration was 1248.9 ± 91.4 (range 217.7-4100.1) pg mL-1. In general, the levels of 17ß-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.

New Echinoderm-Crab Epibiotic Associations from the Coastal Barents Sea.

During diving surveys for a Russian research project that monitored introduced species, red king crabs (Paralithodes camtschaticus) were collected at a coastal site of the Barents Sea to study the structure and dynamics of this species. Sampling of the organisms colonizing the crabs was part of this research project. For the first time, the presence of relatively large specimens of the common starfish Asterias rubens as epibionts of P. camtschaticus was observed in July 2010, 2018, and 2019. In 2010 and 2019, we also found three other echinoderm species (the Atlantic sea cucumber Cucumaria frondosa, the green sea urchin Strongylocentrotus droebachiensis, and the brittle star Ophiura sarsii). These findings add to the current list of associated species on king crabs not only in the Barents Sea but also in native areas of this host. Red king crabs have been documented as predators for these echinoderm species, and our records show additional possible interactions between king crabs and echinoderms in this region. More likely, the epibiotic lifestyle allows these echinoderms to avoid predation from red king crabs. There are no potential disadvantages derived by red king crabs through their relationships with the echinoderm epibionts due to low occurrences of these associations. We suggest no negative effects for the local red king crab population and populations of other commercial species in the Barents Sea.