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This paper describes the associated fauna of the deep-sea gorgonian corals Paragorgia arborea and Primnoa resedaeformis. Composition and distribution of this fauna is described based on material from the continental shelf and slope off Atlantic Canada (300–600 m depth). Samples were collected from five areas with Remotely Operated Vehicle, video grab, and bottom trawl. The collected material consists of 25 samples, 13 from P. arborea and 12 from P. resedaeformis. A total of 114 species and 3915 individuals were recorded. The P. resedaeformis fauna was more abundant and diverse than the fauna of P. arborea, with 2651 specimens and 97 species found on the former and 1264 specimens and 47 species on the latter. Rarefaction analysis indicated that many more associated species are still to be found. Species richness and abundance was significantly correlated with coral morphology (e.g., number of branches, wet weight, and % exposed skeleton). Crustaceans dominated the fauna, contributing 46 % to the total number of individuals and 26 % to the total number of species. Two coral microhabitats were identified: 1) young and live parts of colonies and, 2) old parts with deposits and exposed skeleton. Most of the associated fauna was found in the latter habitat. There was a clear difference in fauna composition of the two coral species. Sessile hydroids, anemones, and molluscs were more abundant on P. resedaeformis. These organisms occurred attached to the hard substratum provided by the exposed skeleton. Parasitic copepods and polychaetes were more common on P. arborea. Two copepods, a lichomolgid ecto-parasite and a lamippid gall-forming endoparasite, were associated with P. arborea. The echinoderm Gorgonocephaluslamarckii was found in the high current environment on the outer branches of P. arborea. The shrimp Pandalus propinquus was hiding and resting on colonies of both coral species. Many of the associated taxa are also found on tropical gorgonians but the deepsea gorgonians lack the diverse decapod and gastropod-fauna of their tropical counterparts. The species richness of the deep-sea gorgonian coral fauna was higher than what has been observed for tropical gorgonians. In contrast to the tropical associates very few are obligate symbionts. Nevertheless, several of the species are rare in other habitats and have been recorded on the same and other gorgonian species in early studies from the eastern North Atlantic. The sampling gear collected the fauna differently. Corals from bottom trawls had a poorer associated fauna that differed in composition with material collected by ROV or video assisted grab. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]