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The deep sea plays a critical role in global climate regulation through uptake and storage of heat and carbon dioxide. However, this regulating service causes warming, acidification and deoxygenation of deep waters, leading to decreased food availability at the seafloor. These changes and their projections are likely to affect productivity, biodiversity and distributions of deep-sea fauna, thereby compromising key ecosystem services. Understanding how climate change can lead to shifts in deep-sea species distributions is critically important in developing management measures. We used environmental niche modelling along with the best available species occurrence data and environmental parameters to model habitat suitability for key cold-water coral and commercially important deep-sea fish species under present-day (1951-2000) environmental conditions and to project changes under severe, high emissions future (2081-2100) climate projections (RCP8.5 scenario) for the North Atlantic Ocean. Our models projected a decrease of 28%-100% in suitable habitat for cold-water corals and a shift in suitable habitat for deep-sea fishes of 2.0°-9.9° towards higher latitudes. The largest reductions in suitable habitat were projected for the scleractinian coral Lophelia pertusa and the octocoral Paragorgia arborea, with declines of at least 79% and 99% respectively. We projected the expansion of suitable habitat by 2100 only for the fishes Helicolenus dactylopterus and Sebastes mentella (20%-30%), mostly through northern latitudinal range expansion. Our results projected limited climate refugia locations in the North Atlantic by 2100 for scleractinian corals (30%-42% of present-day suitable habitat), even smaller refugia locations for the octocorals Acanella arbuscula and Acanthogorgia armata (6%-14%), and almost no refugia for P. arborea. Our results emphasize the need to understand how anticipated climate change will affect the distribution of deep-sea species including commercially important fishes and foundation species, and highlight the importance of identifying and preserving climate refugia for a range of area-based planning and management tools.

Deep-sea sponge grounds are distributed globally and are considered hotspots of biological diversity and biogeochemical cycling. To date, little is known about the environmental constraints that control where deep-sea sponge grounds occur and what conditions allow high sponge biomass to develop in the deep sea. Here, we characterize oceanographic conditions at two contrasting high- and low-sponge-biomass sites off the northern Labrador Shelf in Canadian waters. Unique data for the region were collected by year-long benthic lander deployments equipped with current meters, turbidity and chlorophyll-a sensors, and sediment traps. Additionally, the regional oceanography was described by analysing vertical conductivity/salinity-temperature-depth (CTD) and Argo float profiles for the Northern Labrador Shelf from 2005 to 2022, including those from the CTD casts taken at the benthic lander stations. Benthic fauna stable isotopes were analysed to identify potential food sources. Our results revealed strong (0.26 ± 0.14 m s-1; mean ± SD) semidiurnal tidal currents at the high-sponge-biomass site, but twofold weaker currents (0.14 ± 0.08 m s-1; mean ± SD) at the low-sponge-biomass site. These tidal currents cause periodic temperature fluctuations, sediment resuspension, intense vertical flows across the slope, which during spring, contribute to transport of organic material to the seafloor during a diurnal tidal cycle. Periodic fluctuations in bottom water temperature confirm the amplified transport across the shelf break at the high-sponge-biomass site. The high-sponge-biomass area is situated where the Hudson Strait Ouflow, the Irminger Current, and the West Greenland Current converge, which could lead to downwelling. Bottom silicate concentrations were increased at the high-biomass sponge ground due to advection of silicate-rich bottom water from Baffin Bay. Finally, the arrival of chlorophyll-a rich material in spring at both the low- and high-sponge-biomass sites demonstrated tight benthic-pelagic coupling prior to the onset of stratification. Mass fluxes of trapped material were higher and consisted of less degraded material at the high-sponge-biomass site. Stable isotope signatures indicated that soft corals (Primnoa resedaeformis) fed on suspended particulate organic matter, while massive sponges (Geodia spp.) likely utilized additional food sources. Our results imply that benthic fauna at the high-sponge-biomass site benefit from strong tidal currents, which increases food supply, and favourable regional ocean currents that increase nutrient concentration in bottom waters. [ABSTRACT FROM AUTHOR]

Abstract--Fish species of the Middle Atlantic Bight (MAB) continental shelf are well known; however, species occupying hard-bottom habitats, particularly on the outer shelf, are poorly documented. Reef-like habitats are relatively [...]

Living colonies of the cold-water scleractinian coral Lophelia pertusa and other typically deep-water organisms were discovered in unusually shallow depths (180-250 m) off northeastern Florida. Observations of L. pertusa on rocky substrata and coral-built mounds represent the shallowest records of large colonies of this coral in the western Atlantic Ocean. Biohenns up to 30 m tall, extensive areas of eroded L. pertusa rubble, and a well-developed cold-water community indicated that these sites are long-term features, rather than short-term opportunistic responses to temporary shifts in environmental conditions. Species that are commonly observed on deeper reefs off the southeastern USA were abundant at the shallow sites. The most abundant fishes on reef habitats were Helicolenus dactylopterus, Laemonema barbatulum, Dysommina rugosa, and Anthias spp. In addition to L. pertusa, the most common macroinvertebrates on hard substrata were Eumunida picta, Chaceon fenneri, octocorals, cup corals, and glass sponges. Bottom and near-bottom temperatures (7-10°C) and nutrient concentrations at the shallow sites were similar to those normally encountered at 500-600 m in this region. The shallow reef sites occur in an area known for frequent Gulf Stream-driven upwelling of deep, nutrient-rich water. However, the upwelling must be persistent or permanent in order to maintain deep-sea communities at such shallow depths. Based on these data, this area is under final review by the US Department of Commerce for inclusion in one of the regional Coral Habitat Areas of Particular Concern., Introduction The deep sea is usually defined as waters deeper man 200 m. However, boundaries between marine ecosystems are difficult to delineate, as fauna and environmental characteristics grade from one [...]

Abstract--Citharichthys cornutus and C. gymnorhinus, diminutive flatfishes inhabiting continental shelves in the western Atlantic Ocean, are infrequently reported and poorly known. We identified 594 C. cornutus in 56 different field [...]

Abstract--The community structure of fishes associated with pelagic Sargassum spp. and open water lacking Sargassum was examined during summer and fall cruises, 1999-2003, in the Gulf Stream off North Carolina. [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2007.03.010 Byline: Steve W. Ross, Andrea M. Quattrini Keywords: Deep-sea corals; Southeastern USA; Blake Plateau; Deep-reef fishes; Lophelia Abstract: Deep-sea or cold-water corals form substantial habitat along many continental slopes, including the southeastern United States (SEUS). Despite increasing research on deep coral systems and growing appreciation of their importance to fishes, quantitative data on fish communities occupying these ecosystems are relatively lacking. Our overall goals were to document the fish species and their relative abundances and to describe the degree of general habitat specificity of the fishes on and around deep coral habitats on the SEUS slope. From 2000 to 2006, we used the Johnson-Sea-Link (JSL) submersible (65 dives, 366-783m), supplemented with otter trawls (33 tows, 365-910m) to document fishes and habitats from off North Carolina to east-central Florida. Eight areas with high concentrations of deep-sea corals were surveyed repeatedly. Three general habitat types (prime reef, transition reef, and off reef) were defined to determine large-scale habitat use patterns. Throughout the area, at least 99 fish species were identified, many (19%) of which yielded new distributional data. Most species observed with the JSL were on prime reef (n=50) and transition reef (n=42) habitats, but the off reef habitat supported a well developed, but different fauna (n=25 species). Prime reef was characterized by Laemonema melanurum (21% of total), Nezumia sclerorhynchus (17% of total), Beryx decadactylus (14% of total), and Helicolenus dactylopterus (10% of total). The off reef areas were dominated by Fenestraja plutonia (19% of total), Laemonema barbatulum (18% of total), Myxine glutinosa (8% of total), and Chlorophthalmus agassizi (7% of total). Transition habitat exhibited a mixture of species that were also found on either prime reef or off reef habitats. Nezumia sclerorhynchus was the most abundant (25% of total) transition habitat species, followed by L. barbatulum (16% of total) and L. melanurum (14% of total). Several species (e.g., Anthias woodsi, B. decadactylus, Conger oceanicus, and Dysommina rugosa) demonstrated specificity to deep-reef habitats, while others (e.g., C. agassizi, Benthobatis marcida, F. plutonia, and Phycis chesteri) were always more common away from reefs. In addition to new distributional data, we provide behavioral and biological observations for dominant species. Author Affiliation: University of North Carolina Wilmington, Center for Marine Science, 5600 Marvin K. Moss Lane, Wilmington, NC 28409, USA Article History: Received 2 December 2006; Revised 12 March 2007; Accepted 14 March 2007

Abstract--Offshore winter-spawned fishes dominate the nekton of southeastern United States estuaries. Their juveniles reside for several months in shallow, soft bottom estuarine creeks and bays called primary nursery areas. Despite [...]