Northeast U.S. Atlantic Canyons

In the late 1970’s through 1987, the Mineral Management Service funded a series of studies that addressed biological and physical processes of the eastern US continental margin. The initial study, the Canyon Assessment Study (CAS) (Hecker, Blechschmidt, and Gibson, 1980), had a particular emphasis on deep-water corals. This study consisted of two parts: a historical component that reviewed 79 submersible dives and 33 camera lowerings and a field component that consisted of 18 camera sled tows in 3 canyons, specifically Baltimore, Oceanographer, and Lydonia Canyons (Hecker and Blechschmidt, 1980). This study confirmed that in addition to standard slope fauna, canyons also support deep-water coral communities, as well as a number of other sessile filter feeders.

A subsequent study, the Canyon and Slope Processes Study (CASPS) (Lamont-Doherty Geological Observatory, 1983) focused on the biological and physical processes of slope and canyon areas. This study included investigations of canyon versus slope currents, hydrography, and suspended sediment transport patterns, as well as megafaunal distributions and community structure. Baltimore Canyon and the slopes between Linderkohl and Carteret Canyons (Slope I), and between Toms and Meys Canyons (Slope II) were surveyed in the Mid-Atlantic region, and Lydonia Canyon and the slope between Veatch and Hydrographer Canyons (Slope III) were surveyed in the North Atlantic region. Major findings were that the shallower part of Baltimore Canyon and much of Lydonia Canyon supported diverse assemblages of filter feeders in addition to taxa typically found on the slope. The filter feeding assemblages consisted mainly of deep-water corals, sponges and anemones. Taxonomic richness was also found to be higher in areas of exposed hard substrate. Trophic patterns were more complex in canyon habitats owing to the addition of filter-feeding taxa in both soft and hard substrate areas. As a result of this study, canyon habitats were identified as quite heterogeneous with enhanced current flows and particle transport, thus providing habitats or “refuges” for a variety of unique sessile taxa (sponges, anemones, corals). Additionally, as a result of their spatially restricted distributions these populations were viewed to be “fragile” with regard to environmental perturbations.

Since July 2012, we have utilized high-quality multibeam data from ACUMEN mapping expeditions, Remotely-Operated Vehicles and the towed camera system TowCam to understand the composition, distribution, diversity, and habitat relationships (using predictive modeling) of deep-water canyon corals, sponges and fish. We have focused on groundtruthing predicted habitats, including high-relief bottom features likely serving as coral habitat. Mapping and slope estimate results from our recently developed habitat suitability model (Brian Kinlan, lead). These models use various physical and biological data to predict where corals are likely to occur based on conditions found in locations where corals were previously reported. Over the past 6 years, we have conducted more than 90 towed camera surveys and more than 20 ROV dives in more than 25 major and minor canyons and our ongoing work has discovered differences in coral composition and diversity with depth within individual canyons, strong links to specific habitat types, and faunal and habitat differences among canyons.

Submarine canyons are important, productive habitats in the deep sea. Submarine canyons act as downslope conduits for transport of sediments and organic materials that enhance local and regional species diversity, as well as accumulation of marine debris. We are documenting and characterizing deep-sea coral and sponge ecosystems in virtually unexplored northeast and mid-Atlantic canyons using WHOI’s towed imaging system TowCam on the FSV Henry B. Bigelow. Specifically, more than 30 canyons have been surveyed, yielding more than 130,000 seafloor images. In addition to deep-sea coral and sponge habitats, anthropogenic debris is being documented. Canyons surveyed cover a significant latitudinal range of the northeast US region, specifically, Toms Canyon complex, Ryan, Veatch, Gilbert, Powell, and Munson canyons. Each of these canyons hosts debris across depths of ~550 to 2100m, consisting mostly of plastics, metal and fishing gear, including fishing lines, traps, and nets. Potentially land-based debris (e.g., plastic bags and milk cartons) is also present in all canyons surveyed. Marine litter likely enhances colonization and often served as habitat for specific sessile and mobile species. Comparisons of debris in these canyons is revealing depth-related differences, likely due to offshore extent of fishing activities. The occurrence and types of anthropogenic debris observed on Northeast US canyon floors suggests offshore fishing-related and shipping activities are a potential source for these materials. Additionally, debris from near-shore zones may be transported through entrainment in bottom currents.