An examination of the distribution, abundance, and habitat preferences of soft corals (Octocorallia: Alcyonacea) in offshore Nova Scotian waters

Abstract

Cold-water corals have been observed in Atlantic Canada since the 1800’s and to date, there are 31 confirmed species. Although research on cold-water corals in Atlantic Canada has increased over the last two decades, knowledge gaps remain, especially surrounding soft corals (Octocorallia: Alcyonacea). In light of Canada’s recent efforts to protect significant and representative marine ecosystems, more detailed information pertaining to soft corals is needed. This study aimed to increase our knowledge of the various species of soft corals, and specifically their distribution, abundance, and habitat preferences offshore Nova Scotia by using coral samples, interpolated geospatial surfaces, and environmental data collected between 2001-2011 and in 2017 by Fisheries and Oceans Canada during their annual multi-species bottom trawl surveys. The trawl surveys were conducted on the Scotian Shelf, Scotian Slope, and Bay of Fundy. Eight species, Gersemia rubiformis, Gersemia fruticosa, Drifa glomerata, Drifa sp.2, Duva florida, Anthomastus grandiflorus, Heteropolypus sol, and Pseudoanthomastus agaricus belonging to two families, Nephtheidae and Alcyoniidae, were identified. The majority, 62%, of sampled colonies were Gersemia rubiformis. The spatial distribution of all soft coral species displayed a strong affiliation with the northeastern portion of the Scotian Shelf and Scotian Slope. However, the Nephtheidae species are most common on the shelf while the Alcyoniidae species are most common on the shelf edge. This northeastern affiliation may be attributed to the colder temperatures, 1.8–4.3°C, exhibited on the northeastern Scotian Shelf and Scotian Slope compared to the warmer temperatures, 5.8–10.4°C, exhibited on the southwestern portions, and may indicate a preference of soft corals to colder temperatures.

Keywords: Soft corals, distribution, abundance, habitat preferences, Northwest Atlantic Ocean