Deep-water corals and their habitats in The Gully, a submarine canyon off Atlantic Canada

Submarine canyons are structurally complex habitats known to support high densities and diversity of megafaunal organisms. This study describes deepwater corals and their habitats in The Gully, the largest submarine canyon in eastern North America, situated at the Canadian margin off Nova Scotia. Video recordings of the seabed were made along 49 transects, at depths between 110 and 544 m, using a tethered video camera system. The Gully has a high diversity of habitats with steep bedrock outcrops, high relief bottom with ledges of semi-consolidated mudstone, as well as level soft bottoms and areas with gravel. In total 95 megafaunal taxa were observed of which 16 species were corals. There was a strong, positive correlation between the total number of megafaunal taxa and number of coral species along transects, suggesting that coral diversity is a good indicator for overall megafaunal diversity. Corals were present in most parts of the canyon, and up to 11 species were observed along a single transect. The distribution patterns of corals were mainly related to distance along the axis from the canyon head and type of seabed substratum. The highest abundance of corals was found on the western side in the outer part of the canyon and is probably related to circulation patterns with a higher load of particulate matter in the out-fl owing water. Nephtheid soft corals, mainly Duva florida, were most frequent and were found within the whole depth range. Gorgonian corals were observed only deeper than 340 m. Except for Acanella arbuscula and Radicipes gracilis, which are anchored in mud, the gorgonians were mainly confined to areas with cobble and boulder and in a few cases to semiconsolidated mudstone. Multivariate analyses were applied to identify groups of transects and species, and to indicate which environmental factors control the distribution of corals and other megafauna in The Gully.

[1]  S. Hooker,et al.  Population size and residency patterns of northern bottlenose whales (Hyperoodon ampullatus) using the Gully, Nova Scotia , 2000, J. Cetacean Res. Manage..

[2]  Jan Helge Fosså,et al.  Trawling damage to Northeast Atlantic ancient coral reefs , 2002, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[3]  Fred N. Spiess,et al.  Corals on seamount peaks provide evidence of current acceleration over deep-sea topography , 1986, Nature.

[4]  H. Zibrowius.  Les scléractiniaires de la Méditerranée et de l'Atlantique nord-oriental , 1980 .

[5]  P. Dayton,et al.  Macrofaunal communities within and adjacent to a detritus-rich submarine canyon system , 1998 .

[6]  C. Schönwiese,et al.  Overview of Results , 1997 .

[7]  A. Watson,et al.  Deep-water renewal in the northern North Atlantic , 1990, Nature.

[8]  Claude E. Shannon,et al.  The Mathematical Theory of Communication , 1950 .

[9]  M. Foreman,et al.  Physical and biological processes over a submarine canyon during an upwelling event , 2001 .

[10]  B. Hargrave,et al.  Benthic epifauna assemblages, biomass and respiration in The Gully region on the Scotian Shelf, NW Atlantic Ocean , 2004 .

[11]  G. Steeves,et al.  Canadian imaging and sampling technology for studying marine benthic habitat and biological communities , 2000 .

[12]  Sang Joon Kim,et al.  A Mathematical Theory of Communication , 2006 .

[13]  P. B. Mortensen,et al.  Deep water bioherms of the scleractinian coral Lophelia pertusa (L.) at 64° n on the Norwegian shelf: Structure and associated megafauna , 1995 .

[14]  Alex D. Rogers,et al.  The Biology of Lophelia pertusa (Linnaeus 1758) and Other Deep‐Water Reef‐Forming Corals and Impacts from Human Activities. , 1999 .

[15]  A. L. Rice,et al.  Dense aggregations of a hexactinellid sponge, Pheronema carpenteri, in the Porcupine Seabight (northeast Atlantic Ocean), and possible causes , 1990 .

[16]  Ole Secher Tendal,et al.  The North Atlantic distribution of the octocoral Paragorgia arborea (L., 1758) (Cnidaria, Anthozoa) , 1992 .

[17]  Lene Buhl-Mortensen,et al.  Distribution and diversity of species associated with deep-sea gorgonian corals off Atlantic Canada , 2005 .

[18]  Eric W. Vetter.  Hotspots of benthic production , 1994, Nature.

[19]  Jan Helge Fosså,et al.  Distribution, abundance and size of Lophelia pertusa coral reefs in mid-Norway in relation to seabed characteristics , 2001, Journal of the Marine Biological Association of the United Kingdom.

[20]  H. Westerberg,et al.  The distribution of the scleractinian coral Lophelia pertusa around the Faroe islands and the relation to internal tidal mixing , 1992 .

[21]  Lene Buhl-Mortensen,et al.  Distribution of deep-water gorgonian corals in relation to benthic habitat features in the Northeast Channel (Atlantic Canada) , 2004 .

[22]  S. Cairns.  Scleractinia of the Temperate North Pacific , 1994 .

[23]  Oliver C Peppe,et al.  Monitoring environmental variability around cold-water coral reefs: the use of a benthic photolander and the potential of seafloor observatories , 2005 .

[24]  J. Willison,et al.  An assessment of the distribution of deep-sea corals in Atlantic Canada by using both scientific and local forms of knowledge , 2005 .

[25]  A. E. Verrill.  Mollusks, Echnioderms, Coelenterates, etc. Part G Alcyonaria and Actinaria / , 2022 .

[26]  L. Buhl‐Mortensen,et al.  Crustaceans associated with the deep-water gorgonian corals Paragorgia arborea (L., 1758) and Primnoa resedaeformis (Gunn., 1763) , 2004 .

[27]  P. B. Mortensen,et al.  The deep-water coral Lophelia pertusa in Norwegian waters: distribution and fishery impacts , 2002, Hydrobiologia.

[28]  C. Wentworth.  A Scale of Grade and Class Terms for Clastic Sediments , 1922, The Journal of Geology.