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Using data from a number of summer surveys of the Chukchi Sea over the past decade, we investigate aspects in which the benthic fauna, sediment structure, and zooplankton there are related to circulation patterns and shelf hydrographic conditions. A flow speed map is constructed that reveals the major pathways on the shelf. Regions of enhanced flow speed are dictated by lateral constrictions--in particular, Bering Strait and Barrow and Herald Canyons--and by sloping topography near coastlines. For the most part, benthic epifaunal and macrofaunal suspension feeders are found in high flow regimes, while deposit feeders are located in regions of weaker flow. The major exceptions are in Bering Strait, where benthic sampling was underrepresented, and in Herald Canyon where the pattern is inexplicably reversed. Sediment grain size is also largely consistent with variations in flow speed on the shelf. Data from three biophysical surveys of the Chukchi Sea, carried out as part of the Russian-American Long-term Census of the Arctic program, reveal close relationships between the water masses and the zooplankton communities on the shelf. Variations in atmospheric forcing, particularly wind, during the three sampling periods caused significant changes in the lateral and vertical distributions of the summer and winter water masses. These water mass changes, in turn, were reflected in the amounts and species of zooplankton observed throughout the shelf in each survey. Our study highlights the close relationship between physical drivers (wind forcing, water masses, circulation, and sediment type) in the Chukchi Sea and the biological signals in the benthos and the plankton on a variety of time scales. [ABSTRACT FROM AUTHOR]

Abstract: The benthic component of an interdisciplinary expedition on icebreaker USCG HEALY analyzed box core samples and seafloor photographs to quantify deep-sea assemblages in the Canada Basin and Chukchi Borderland area. Soft bottom metazoan macrofauna (>250μm) were collected with 33 box cores at 11 stations ranging from 817 to 3961m water depth in the high-Arctic Canada Basin from 28 June to 25 July 2005. Megabenthic epifauna was quantified with a digital camera platform suspended <5m above the bottom at six stations (940–3800m water depth), of which the shallowest and northernmost one targeted a pockmark ∼40m deep by 800m wide. A total of 99 macrofauna taxa were identified, including at least three previously undescribed species of polychaetes. Total macrofauna abundance ranged from 0.6 to 50 individuals 0.06m−2 (89–2722indm−2) and total biomass ranged from 0.2 to 1.6g wet weight 0.06m−2 (<0.1–26.1gwetweightm−2). Macrofauna diversity numbered between 8 and 55 taxa per station. Abundance, biomass, number of taxa, and diversity indices of macrofauna declined significantly with water depth. Polychaetes, crustaceans and bivalves dominated the macrofaunal densities, biomass and species numbers. The megafauna visible in the seabed photographs was assigned to a total of 67 provisional taxa; the lowest taxon count per station was 11, and the highest was 51 at the pockmark station. Epifauna abundance was also highest in this pockmark (mean 5.8indm−2) and generally lower at deepest stations (0.1–0.9indm−2), but was skewed by large numbers of the holothuroid Kolga hyalina. Epifauna observed in the center of the pockmark was significantly different from all other station groups, but did not include known chemosynthetic fauna or bacterial mats. Multivariate analysis indicated that station groupings “Chukchi slope”, “Canada Basin abyss” and the “Chukchi Cap” were significantly different in community composition in the macrofauna box corer samples, but could not be similarly distinguished as such in the epifauna photographs. [Copyright &y& Elsevier]

Abstract: The abundances and distribution of metazoan within-ice meiofauna (13 stations) and under-ice fauna (12 stations) were investigated in level sea ice and sea-ice ridges in the Chukchi/Beaufort Seas and Canada Basin in June/July 2005 using a combination of ice coring and SCUBA diving. Ice meiofauna abundance was estimated based on live counts in the bottom 30cm of level sea ice based on triplicate ice core sampling at each location, and in individual ice chunks from ridges at four locations. Under-ice amphipods were counted in situ in replicate (N=24–65 per station) 0.25m2 quadrats using SCUBA to a maximum water depth of 12m. In level sea ice, the most abundant ice meiofauna groups were Turbellaria (46%), Nematoda (35%), and Harpacticoida (19%), with overall low abundances per station that ranged from 0.0 to 10.9indl−1 (median 0.8indl−1). In level ice, low ice algal pigment concentrations (<0.1–15.8μgChl a l−1), low brine salinities (1.8–21.7) and flushing from the melting sea ice likely explain the low ice meiofauna concentrations. Higher abundances of Turbellaria, Nematoda and Harpacticoida also were observed in pressure ridges (0–200indl−1, median 40indl−1), although values were highly variable and only medians of Turbellaria were significantly higher in ridge ice than in level ice. Median abundances of under-ice amphipods at all ice types (level ice, various ice ridge structures) ranged from 8 to 114indm−2 per station and mainly consisted of Apherusa glacialis (87%), Onisimus spp. (7%) and Gammarus wilkitzkii (6%). Highest amphipod abundances were observed in pressure ridges at depths >3m where abundances were up to 42-fold higher compared with level ice. We propose that the summer ice melt impacted meiofauna and under-ice amphipod abundance and distribution through (a) flushing, and (b) enhanced salinity stress at thinner level sea ice (less than 3m thickness). We further suggest that pressure ridges, which extend into deeper, high-salinity water, become accumulation regions for ice meiofauna and under-ice amphipods in summer. Pressure ridges thus might be crucial for faunal survival during periods of enhanced summer ice melt. Previous estimates of Arctic sea ice meiofauna and under-ice amphipods on regional and pan-Arctic scales likely underestimate abundances at least in summer because they typically do not include pressure ridges. [Copyright &y& Elsevier]

Abstract The Arctic's Barrow Canyon, located in the northeastern Chukchi and western Beaufort seas, supports a rich and diverse benthic ecosystem and is often termed an ecological "hotspot" of productivity. Within and adjacent to Barrow Canyon, the epibenthic invertebrate communities vary, with biomass and taxonomic distributions related to habitat variation. Here we asked if the patterns observed are due to Barrow Canyon's variation in near-seafloor physical hydrography, and whether differences in taxonomic distribution also reflect differences in functional properties of the epibenthic invertebrate community. Data were collected using a standardized 83–112 bottom trawl during two surveys in and adjacent to Barrow Canyon: the northeast Chukchi Sea survey in 2013 and the western Beaufort Sea survey in 2008. A portion of the Beaufort Sea survey also used a liner to retain smaller organisms. A suite of nine environmental variables were examined, that included depth, bottom water temperature, bottom hardness as measured by acoustics, and circulation model hindcast current speed. They explained 18–47% of observed variance for each of the three data sets (Chukchi Sea, Beaufort Sea lined net (LN), Beaufort Sea unlined net (UN)). In the Chukchi Sea, bottom hardness and depth were significant variables. In the Beaufort Sea LN hauls, depth, bottom temperature, and the mean current speed on the day of sampling were significant variables and in the Beaufort Sea UN hauls, depth was the only significant variable. Of the 150+ collected taxa from each survey, ~20 made up 90% of the total biomass in the Beaufort and Chukchi Seas, and six of the 20 taxa were common to both study areas. We used biological traits analysis (BTA) of body morphology, trophic, and reproductive traits to further characterize the epibenthos at the head of Barrow Canyon in the Chukchi Sea and into Barrow Canyon in the Beaufort Sea. Although the Chukchi and Beaufort seas differed taxonomically in abundance and distribution, they were functionally similar based on the biological traits we examined. A traits analysis can advance knowledge of a community of organisms; however, it is most informative if used as a complement to a taxonomic composition analysis of abundance and distribution. [ABSTRACT FROM AUTHOR]

One of the logical predictions for a future Arctic characterized by warmer waters and reduced sea-ice is that new taxa will expand or invade Arctic seafloor habitats. Specific predictions regarding where this will occur and which taxa are most likely to become established or excluded are lacking, however. We synthesize recent studies and conduct new analyses in the context of climate forecasts and a paleontological perspective to make concrete predictions as to relevant mechanisms, regions, and functional traits contributing to future biodiversity changes. Historically, a warmer Arctic is more readily invaded or transited by boreal taxa than it is during cold periods. Oceanography of an ice-free Arctic Ocean, combined with life-history traits of invading taxa and availability of suitable habitat, determine expansion success. It is difficult to generalize as to which taxonomic groups or locations are likely to experience expansion, however, since species-specific, and perhaps population-specific autecologies, will determine success or failure. Several examples of expansion into the Arctic have been noted, and along with the results from the relatively few Arctic biological time-series suggest inflow shelves (Barents and Chukchi Seas), as well as West Greenland and the western Kara Sea, are most likely locations for expansion. Apparent temperature thresholds were identified for characteristic Arctic and boreal benthic fauna suggesting strong potential for range constrictions of Arctic, and expansions of boreal, fauna in the near future. Increasing human activities in the region could speed introductions of boreal fauna and reduce the value of a planktonic dispersal stage. Finally, shelf regions are likely to experience a greater impact, and also one with greater potential consequences, than the deep Arctic basin. Future research strategies should focus on monitoring as well as compiling basic physiological and life-history information of Arctic and boreal taxa, and integrate that with projections of human activities and likely ecosystem consequences to facilitate development of management strategies now and in the future. [ABSTRACT FROM AUTHOR]