Exploration of the Canyon-Incised Continental Margin of the Northeastern United States Reveals Dynamic Habitats and Diverse Communities

Abstract

The continental margin off the northeastern United States (NEUS) contains numerous, topographically complex features that increase habitat heterogeneity across the region. However, the majority of these rugged features have never been surveyed, particularly using direct observations. During summer 2013, 31 Remotely-Operated Vehicle (ROV) dives were conducted from 494 to 3271 m depth across a variety of seafloor features to document communities and to infer geological processes that produced such features. The ROV surveyed six broad-scale habitat features, consisting of shelf-breaching canyons, slope-sourced canyons, inter-canyon areas, open-slope/landslide-scar areas, hydrocarbon seeps, and Mytilus Seamount. Four previously unknown chemosynthetic communities dominated by Bathymodiolus mussels were documented. Seafloor methane hydrate was observed at two seep sites. Multivariate analyses indicated that depth and broad-scale habitat significantly influenced megafaunal coral (58 taxa), demersal fish (69 taxa), and decapod crustacean (34 taxa) assemblages. Species richness of fishes and crustaceans significantly declined with depth, while there was no relationship between coral richness and depth. Turnover in assemblage structure occurred on the middle to lower slope at the approximate boundaries of water masses found previously in the region. Coral species richness was also an important variable explaining variation in fish and crustacean assemblages. Coral diversity may serve as an indicator of habitat suitability and variation in available niche diversity for these taxonomic groups. Our surveys added 24 putative coral species and three fishes to the known regional fauna, including the black coral Telopathes magna, the octocoral Metallogorgia melanotrichos and the fishes Gaidropsarus argentatus, Guttigadus latifrons, and Lepidion guentheri. Marine litter was observed on 81% of the dives, with at least 12 coral colonies entangled in debris. While initial exploration revealed the NEUS region to be both geologically dynamic and biologically diverse, further research into the abiotic conditions and the biotic interactions that influence species abundance and distribution is needed.

Insights into methane dynamics from analysis of authigenic carbonates and chemosynthetic mussels at newly-discovered Atlantic Margin seeps

“…2C and 3D) during the 2012 and 2013 ROV dives. Clams, common at the Blake Ridge seep site (Van Dover et al, 2003), were notably absent, as were tubeworms, a finding that is consistent with a recent survey of chemosynthetic communities from seep sites along the northeastern US continental margin (Quattrini et al, 2015). Seep communities at the Norfolk and Baltimore Canyon seep fields were dominated by the deep-sea mussels of the genus Bathymodiolus, which depends on chemosynthetic endosymbiotic bacteria to oxidize sulfur and/or methane for nutrition (Duperron et al, 2011).…”

“…Observations at a few of the sites from remotely operated vehicles (ROV) included bubble streams, bacterial mats, chemosynthetic communities, authigenic carbonates, deep-sea corals, and gas hydrate (Skarke et al, 2014;Quattrini et al, 2015). Average contemporary methane emissions from seeps along the entire northern USAM are estimated at ∼15 to 90 Mg yr −1 (equivalent to 0.95 to 5.66 × 10 6 mol yr −1 ) based on analysis of ROV bubble observations (Skarke et al, 2014), versus 2.15 to 8.65 × 10 6 mol yr −1 in a seep field of Hudson Canyon based on the water column methane concentrations (Weinstein et al, submitted for publication).…”

Characterization of Methane-Seep Communities in a Deep-Sea Area Designated for Oil and Natural Gas Exploitation Off Trinidad and Tobago

“…), and other fauna (Figure 3). Here the authigenic carbonates are used by benthic background fauna as a source of hard substrate and shelter, and also provide access to food through the position in the current (Olu et al, 1996;Quattrini et al, 2015;Levin et al, 2016). Beyond that ecotone were sedimented areas that had a different faunal assemblage mostly comprised of deposit feeders (Figure 3).…”

Ecological Role of Submarine Canyons and Need for Canyon Conservation: A Review

“…Submarine canyons are one of these habitats. Recent novel technological developments including underwater acoustic mapping, imaging, and sampling technologies, and long-term/permanent moored or benthic observatories, have greatly contributed to our understanding of the diverse and complex hydrodynamics (Xu, 2011) and geomorphology of canyons over the last two decades (Robert et al, 2014;Quattrini et al, 2015), allowing the spatiotemporal tracking of oceanographic processes and the associated biological responses, with an integration level that grows every day (Aguzzi et al, 2012;Matabos et al, 2014). As a result of prospective surveys, we know that submarine canyons are major geomorphic features of continental margins, with more than 9000 large canyons covering 11.2% of continental slopes globally , with an estimated accumulated axis length of over 25,000 km (Huang et al, 2014).…”