Distributional patterns of deep-sea coral assemblages in three submarine canyons off Newfoundland, Canada

Deep-sea corals are fragile and long-lived species that provide important habitat for a variety of taxa. The rarity of in situ observations in deep waters off Newfoundland, Canada, motivated the first extensive deep-sea research cruise to that region in 2007. We conducted 7 dives in 3 canyons (Haddock Channel, Halibut Channel, and Desbarres Canyon) with ROPOS (Remotely Operated Platform for Ocean Science). Over 160 000 coral colonies were enumerated and, of the 28 species found, Acanella arbuscula, Pennatula spp., and Flabellum spp. were most frequently observed. The largest coral observed was Keratoisis grayi at over 2 m in height. Corals spanned the entire depth range sampled (351 to 2245 m) and inhabited all bottom types surveyed, but boulder and cobble habitats were most species-rich. Assemblages differed significantly with depth class and bottom type. The unique assemblage at outcrops was strongly driven by the presence of Desmophyllum dianthus. Keratoisis grayi, D. dianthus, and Anthomastus spp. were largely absent in mud-sand habitats. Sea pen meadows covered large tracts of muddy seafloor spanning > 1 km. Acanella arbuscula and Flabellum spp. characterised large coral fields with abundant corals but relatively low species richness. These results highlight not only the importance of hard structure in determining patterns of coral distributions, abundances, and assemblages, but also the need to focus conservation efforts on a variety of habitats to ensure protection for the full suite of deep-sea coral species.