Stock Dynamics of Female Red King Crab in a Small Bay of the Barents Sea in Relation to Environmental Factors

Stock-recruitment relationships depend on the total abundance of females, their fecundity, and patterns of their maturation. However, the effects of climatic conditions on the abundance, biomass, and mean weight of female red king crabs, Paralithodes camtschaticus, from the introduced population (Barents Sea) have not yet been studied. For this reason, we analyzed long-term fluctuations in stock indices and the average weight of an individual crab in a small bay of the Barents Sea and related these parameters to the dynamics of temperature conditions (temperature in January-December, mean yearly temperature, and temperature anomaly) in the sea. The average weight of a crab at age 6-9 had strong negative correlations with water temperature at lags 8 and 9, indicating faster female maturation in warm periods. Positive relationships were registered between temperature and stock indices for 15-19-year-old females at lag 4 and for 10-14-year-old females at lag 10, supporting the idea of higher survival rates of juveniles and their rapid development being a response to a pool of warm waters. Both redundancy and correlation analyses revealed seawater temperatures in June-August being the most important predictors of female abundance and biomass, indicating that favorable temperature conditions in the first 3 months of crab benthic life result in high survivorship rates for red king crabs.

The Impact of Sea Ice Loss on Benthic Communities of the Makarov Strait (Northeastern Barents Sea)

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.

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.

Shallow-Water Bryozoan Communities in a Glacier Fjord of West Svalbard, Norway: Species Composition and Effects of Environmental Factors

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.

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.

First Record of Nematode Larvae in the Amphipod Ischyrocerus commensalis Colonizing Red King Crabs in the Barents Sea

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.

Ecology and Distribution of Red King Crab Larvae in the Barents Sea: A Review

The red king crab (RKC) is a large invasive species inhabiting bottom communities in the Barents Sea. Larval stages of RKC play an important role in determining the spread and recruitment of the population in the coastal waters. We present a review of studies concerned with the ecology of RKC larvae in the Barents Sea focusing on their dynamics and role in the trophic food webs as well as on the role of environmental factors in driving RKC zoeae. Zoeal stages are larger, and their development time is shorter in the Barents Sea compared to the North Pacific. RKC larvae appear in late January–February and can be found in the coastal plankton until mid-July. Mass hatching of RKC larvae in the Barents Sea starts in late March-early April. The highest densities of RKC larvae are located in small semi-enclosed bays and inlets with weak water exchange or local eddies as well as in inner parts of fjords. Size structures of the zoeal populations are similar in the inshore waters to the west of Kola Bay but slightly differ from those in more eastern regions. RKC larvae perform daily vertical migrations and move to deeper depths during bright daylight hours and tend to rise during night hours. RKC larvae are plankton feeders that ingest both phyto- and zooplankton. A set of environmental variables including food conditions, water temperature, and advective influence are the most important factors driving the spatial distribution, phenology, survival rates, development, growth, and interannual fluctuations of RKC larvae. Recent climatic changes in the Arctic may have both negative and positive consequences for RKC larvae.