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Recent investigations of demersal fish communities in deepwater (>50 m) habitats have considerably increased our knowledge of the factors that influence the assemblage structure of fishes across mesophotic to deep-sea depths. While different habitat types influence deepwater fish distribution, whether different types of rugged seafloor features provide functionally equivalent habitat for fishes is poorly understood. In the northeastern Caribbean, different types of rugged features (e.g., seamounts, banks, canyons) punctuate insular margins, and thus create a remarkable setting in which to compare demersal fish communities across various features. Concurrently, several water masses are vertically layered in the water column, creating strong stratification layers corresponding to specific abiotic conditions. In this study, we examined differences among fish assemblages across different features (e.g., seamount, canyon, bank/ridge) and water masses at depths ranging from 98 to 4060 m in the northeastern Caribbean. We conducted 26 remotely operated vehicle dives across 18 sites, identifying 156 species of which 42% of had not been previously recorded from particular depths or localities in the region. While rarefaction curves indicated fewer species at seamounts than at other features in the NE Caribbean, assemblage structure was similar among the different types of features. Thus, similar to seamount studies in other regions, seamounts in the Anegada Passage do not harbor distinct communities from other types of rugged features. Species assemblages, however, differed among depths, with zonation generally corresponding to water mass boundaries in the region. High species turnover occurred at depths <1200 m, and may be driven by changes in water mass characteristics including temperature (4.8–24.4 °C) and dissolved oxygen (2.2–9.5 mg per l). Our study suggests the importance of water masses in influencing community structure of benthic fauna, while considerably adding to the knowledge of mesophotic and deep-sea fish biogeography. [ABSTRACT FROM AUTHOR]

Deep-sea corals are the structural foundation of their ecosystems along continental margins worldwide, yet the factors driving their broad distribution are poorly understood. Environmental factors, especially depth-related variables including water mass properties, are thought to considerably affect the realized distribution of deep-sea corals. These factors are governed by local and regional oceanographic conditions that directly influence the dispersal of larvae, and therefore affect the ultimate distribution of adult corals. We used molecular barcoding of mitochondrial and nuclear sequences to identify species of octocorals in the genus Paramuricea collected from the Labrador Sea to the Grand Banks of Newfoundland, Canada at depths of 150–1500 m. The results of this study revealed overlapping bathymetric distributions of the Paramuricea species present off the eastern Canadian coast, including the presence of a few cryptic species previously designated as Paramuricea placomus . The distribution of Paramuricea species in the western North Atlantic differs from the Gulf of Mexico, where five Paramuricea species exhibit strong segregation by depth. The different patterns of Paramuricea species in these contrasting biogeographic regions provide insight into how water mass structure may shape species distribution. Investigating Paramuricea prevalence and distribution in conjunction with oceanographic conditions can help demonstrate the factors that generate and maintain deep-sea biodiversity. [ABSTRACT FROM AUTHOR]

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. [Copyright &y& Elsevier]

Numerous submarine canyons along the United States middle Atlantic continental margin support enhanced productivity, diverse and unique habitats, active fisheries, and are vulnerable to various anthropogenic disturbances. During two cruises (15 Aug–2 Oct 2012 and 30 Apr–27 May 2013), Baltimore and Norfolk canyons and nearby areas (including two cold seeps) were intensively surveyed to determine demersal fish distributions and habitat associations. Overall, 34 ROV dives (234–1612 m) resulted in 295 h of bottom video observations and numerous collections. These data were supplemented by 40, 30-min bottom trawl samples. Fish observations were assigned to five general habitat designations: 1) sand-mud (flat), 2) sloping sand-mud with burrows, 3) low profile gravel, rock, boulder, 4) high profile, canyon walls, rocks or ridges, and 5) seep-mixed hard and soft substrata, the later subdivided into seven habitats based on amounts of dead mussel and rock cover. The influence of corals, sponges and live mussels (seeps only) on fish distributions was also investigated. Both canyon areas supported abundant and diverse fish communities and exhibited a wide range of habitats, including extensive areas of deep-sea corals and sponges and two nearby methane seeps (380–430 m, 1455–1610 m). All methods combined yielded a total of 123 species of fishes, 12 of which are either new records for this region or have new range data. Depth was a major factor that separated the fish faunas into two zones with a boundary around 1400 m. Fishes defining the deeper zone included Lycodes sp., Dicrolene introniger, Gaidropsaurus ensis, Hydrolagus affinis, Antimora rostrata , and Aldrovandia sp. Fishes in the deep zone did not exhibit strong habitat affinities, despite the presence of a quite rugged, extensive methane seep. We propose that habitat specificity decreases with increasing depth. Fishes in the shallower zone, characterized by Laemonema sp., Phycis chesteri, Nezumia bairdii, Brosme brosme , and Helicolenus dactylopterus , exhibited a variety of habitat use patterns. In general, fish assemblages in the soft substrata areas (dominated by P. chesteri, N. bairdii, Glyptocephalus cynoglossus, Lophius americanus, Merluccius albidus ) were different from those in more complex habitats (dominated by Laemonema spp., Hoplostethus spp., B. brosme , Benthocometes robustus, L. americanus, Dysommina rugosa ). Although, when present, the dense coral and sponge cover did not statistically affect general fish assemblage patterns in hard bottom habitats, these sessile organisms markedly increased habitat complexity, and some fish species exhibited close association with them. Fish species compositions in the two canyons were not substantially different from the surrounding slopes. However, the diversity of habitats within both the canyons and seeps exerted an important influence on assemblage structure. At least for some species (e.g., B. brosme ) canyon and seep environments may be a refuge from intensive bottom fishing activities. We frequently observed evidence of commercial and recreational fishing activity (lost gear on bottom and fishing boats in the area) throughout the canyons and some resulting habitat damage. Conservation measures for the unique and more vulnerable areas (seep and coral habitats) have recently been approved. [ABSTRACT FROM AUTHOR]

Abstract: The Lophelia pertusa community at Viosca Knoll (VK826) is the most extensive found to date in the Gulf of Mexico. As part of a multi-disciplinary study, the physical setting of this area was described using benthic landers, CTD transects and remotely operated vehicle observations. The site was broadly characterised into three main habitats: (1) dense coral cover that resembles biogenic reef complexes, (2) areas of sediment, and (3) authigenic carbonate blocks with sparse coral and chemosynthetic communities. The coral communities were dominated by L. pertusa but also contained numerous solitary coral species. Over areas that contained L. pertusa, the environmental conditions recorded were similar to those associated with communities in the north-eastern Atlantic, with temperature (8.5–10.6°C) and salinity (∼35) falling within the known species niche for L. pertusa. However, dissolved oxygen concentrations (2.7–2.8mll−1) and density (σΘ , 27.1–27.2kgm−3) were lower and mass fluxes from sediment trap data appeared much higher (4002–4192mgm−2 d−1). Yet, this species still appears to thrive in this region, suggesting that L. pertusa may not be as limited by lower dissolved oxygen concentrations as previously thought. The VK826 site experienced sustained eastward water flow of 10–30cms−1 over the 5-day measurement period but was also subjected to significant short-term variability in current velocity and direction. In addition, two processes were observed that caused variability in salinity and temperature; the first was consistent with internal waves that caused temperature variations of 0.8°C over 5–11h periods. The second was high-frequency variability (20–30min periods) in temperature recorded only at the ALBEX site. A further pattern observed over the coral habitat was the presence of a 24h diel vertical migration of zooplankton that may form part of a food chain that eventually reaches the corals. The majority of detailed studies concerning local environmental conditions in L. pertusa habitats have been conducted within the north-eastern Atlantic, limiting most knowledge of the niche of this species to a single part of an ocean basin. Data presented here show that the corals at VK826 are subjected to similar conditions in temperature, salinity, and flow velocity as their counterparts in the north-east Atlantic, although values for dissolved oxygen and density (sigma-theta: σΘ ) are different. Our data also highlight novel observations of short-term environmental variability in cold-water coral habitat. [Copyright &y& Elsevier]