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Benthic food‐web structure and organic matter (OM) utilization are important for marine ecosystem functioning. In response to environmental changes related to the ongoing climate change, however, many benthic species are shifting their ranges to colder regions, which may lead to altered community composition, but it remains largely unknown how it will affect ecosystem functioning. Here, stable isotope analysis was used to study benthic OM utilization and food‐web structure and to assess whether their spatial patterns reflect today's community differentiation among biogeographic regions and depth zones. Benthic fauna and OM mixtures were collected from two depth zones (100–150 m vs. 200–250 m) within a temperate, two sub‐Arctic, and an Arctic fjord along a latitudinal gradient (59–78° N) that was used as a space‐for‐time substitution to assess the impact of climate change. Our results showed that Arctic and temperate communities are functionally different. Arctic communities were characterized by a strong resource partitioning among different feeding types, irrespective of depth zone. In contrast, all feeding types in temperate communities seemed to rely on sedimentary OM. The sub‐Arctic presented a transition zone. In the sub‐Arctic, shallower communities resembled Arctic communities, suggesting a functional transition between temperate and sub‐Arctic regions. Deeper sub‐Arctic communities resembled temperate communities, suggesting a functional transition between the sub‐Arctic and Arctic regions. This implies that the regions north of the current transitions (deep Arctic and shallow sub‐Arctic) are most likely to experience functional changes related to an altered OM utilization in benthic food webs in response to climate change. [ABSTRACT FROM AUTHOR]

The Arctic experiences dramatic annual cycles in environmental condition, including winters that can last two thirds of the year. During these long winters, coastal waters are covered in ice and show very low levels of productivity which presumably can be stressful for organisms which remain in the same ecosystem year-round. However, the activities or behavior of marine Arctic residents during this period is not well understood. Fourhorn sculpin (Myoxocephalus quadricornis) are residents of Tremblay Sound, Nunavut, Canada which freezes over entirely from October to June each year. We characterized the behavior of a small number of individuals (n = 7) beneath sea ice with passive acoustic telemetry to monitor position as well as in situ acceleration and depth over time. Intermittent bursts of acceleration and changes in depth usage indicate that sculpins are not dormant under the winter ice and likely continue their characteristic lie-in-wait foraging. A generalized linear mixed model indicated activity increased marginally while individuals moved to shallower waters as spring approached. These behaviors suggest that sculpin could be exploiting early ice-associated productivity before ice melt begins. The continued activity of sculpin even under sea ice provides potential insight to how residents persist in Arctic winters. [ABSTRACT FROM AUTHOR]

An analysis of archival and literary materials, as well as recently collected data in coastal areas at 14 locations in the Eurasian seas showed that the diversity of biomass-dominating key bryozoan species is low, totaling 26 species, less than 1/15 of the total bryozoan fauna richness. Their number decreases eastward from 17 species with an average total biomass of >16 g/m2 in the Barents Sea to three species with an average biomass of about 3 g/m2 in the East Siberian Sea. In the Chukchi Sea, their number and average biomass increase to 10 species and ~12 g/m2, respectively. Average biomass strongly correlates with the number of species in each sea. Furthermore, variation in biomass is significantly correlated with the composition of bottom sediments and, in some locations, with depth. The marked decrease in the number of key species along the vector from Barents→Kara→Laptev→East Siberian Sea is due to a decline in the number of boreal and boreal–Arctic bryozoans of Atlantic origin. In contrast, the appearance of boreal and boreal–Arctic Pacific species is responsible for the increase in key species in the Chukchi Sea. [ABSTRACT FROM AUTHOR]

Accumulation of trimethylamine N-oxide (TMAO) by deep-sea animals is proposed to protect proteins against the destabilizing effects of high hydrostatic pressure (the piezolyte hypothesis). Chondrichthyan fishes (sharks, rays, and chimaeras) provide a unique test of this hypothesis because shallow-living species have elevated TMAO levels to counteract the destabilizing effects of high urea levels accumulated for osmoregulation. Limited interspecific studies of chondrichthyans reveal that increasing depth correlates with decreased urea and increased TMAO levels, suggesting a dynamic balance between destabilizing forces on proteins (high urea, hydrostatic pressure) and TMAO to counteract these forces. Indeed, an inability to minimize urea levels or maximize TMAO levels has been proposed to explain why chondrichthyans are absent in the vast abyssal region. An unresolved question is whether the depth-related changes in chondrichthyan osmolytes are a flexible response to depth or whether phylogenetic differences in species-specific physiological set points for osmolytes account for the differences seen with depth. Sampling Arctic skates (Amblyraja hyperborea) across a 1,015-m depth gradient in the Beaufort Sea, we measured organic osmolytes in muscle using spectrophotometry and high-performance liquid chromatography. We found that the urea-to-TMAO ratio decreased linearly with depth, with tighter correlation than that seen in interspecific studies. Minor osmolytes, including betaine, sarcosine, and some α-amino acids, also declined with depth, apparently replaced (as with urea) by TMAO (a stronger piezolyte than those solutes). These data provide the first intraspecific evidence that flexible adjustments of osmolyte combinations are a key response for deep-sea living in individual chondrichthyans, supporting the piezolyte hypothesis.