Evaluating the relationship between cold-water corals and a cold seep in a submarine slope failure at the Northeast Saglek Bank cold-water coral hotspot, Eastern Canadian Arctic

Multibeam sonar surveys and ROV-based seafloor imagery led to the discovery of active cold seeps associated with a submarine slope failure (SSF), and adjacent high local abundances of the deep-sea coral Primnoa resedaeformis, at northeast Saglek Bank on the glacially influenced northern Labrador Shelf edge. The SSF scar is a 4.5-km long elongate depression, with a ~100-m high scalloped headwall, headscarp slopes ~20-30°, a central ridge containing broken blocks of authigenic carbonate crust, and no visible deposits or compression zone downslope from the scar. Four ROV dives were conducted within and outside the SSF, within depths of 605-818 m. Microbial mats with putative methane- and sulfur-oxidizing bacteria, and authigenic carbonate crusts were observed only in the seep site; on a cobble-boulder gravel substrate, observed at all sites; and near very strong tidally-modulated currents. Coral densities were similar at both sites, but higher local densities were observed at the SSF site, most strongly associated with boulder density. Boulders were the preferred substrate of corals over authigenic carbonate crusts. There was a statistically significant but weak influence of microbial mats on coral distribution. Overall, the spatial association between P. resedaeformis and cold seeps at this local coral hotspot appeared to be coincidental.