A Picture on the Wall: Innovative Mapping Reveals Cold-Water Coral Refuge in Submarine Canyon

Abstract

Cold-water corals are azooxanthellate species found throughout the ocean at water depths down to 5000 m. They occur in patches, reefs or large mound structures up to 380 m high, and as ecosystem engineers create important habitats for a diverse fauna. However, the majority of these habitats are now within reach of deep-sea bottom trawling. Many have been severely damaged or are under threat, despite recent protection initiatives. Here we present a cold-water coral habitat type that so far has been overlooked – quite literally – and that has received minimal impact from human activities. Vertical and overhanging cliffs in deep-sea canyons, revealed using an innovative approach to marine habitat mapping, are shown to provide the perfect substratum for extensive cold-water coral-based communities. Typical canyon-related processes, including locally enhanced internal tides and focussed downslope organic carbon transport, provide favourable environmental conditions (current regime, food input) to sustain the communities, even outside the optimal depth and density envelopes reported elsewhere in the NE Atlantic. Our findings show that deep-sea canyons can form natural refuges for faunal communities sensitive to anthropogenic disturbance, and have the potential to fulfil the crucial role of larval sources for the recolonisation of damaged sites elsewhere on the margin.

Distribution of cold-water corals in the Whittard Canyon, NE Atlantic Ocean

“…Although particulate organic carbon (POC) is directly related to surface production, the preliminary results from the SAPs demonstrate that some areas within the canyon are subject to higher organic input than others. When the POC composition was analysed it was found that the eastern and western branch had different molecular signatures (Huvenne et al, 2011). Changes in the composition of POC input may influence the community structure of the Whittard Canyon, as seen, for instance, on the adjacent abyssal plain (Billett et al, 2001(Billett et al, , 2010.…”

“…The amalgamation of these factors means canyons are often thought of as areas of enhanced biodiversity Vetter et al, 2010). However, very little work has occurred on the biological assemblages and their community structure within canyons, especially cold-water coral assemblages (Huvenne et al, 2011). The present study seeks to increase knowledge on the distribution of deep-sea corals within submarine canyons, focussing on the Whittard Canyon system on the continental margin in the NE Atlantic.…”

Submarine canyons of north-western Sicily (Southern Tyrrhenian Sea): Variability in morphology, sedimentary processes and evolution on a tectonically active margin

“…Submarine canyons are widespread complex features along continental margins and are pathways for sediment transport to the deep basins (Piper and Savoye, 1993;Wynn et al, 2007;Palanques et al, 2012), They play a key role in hydrography, biogeochemistry and carbon cycle dynamics (Epping et al, 2002;Canals et al, 2006;Huvenne et al, 2011). Despite their importance, the processes of start-up, evolution and maintenance of submarine canyons remain poorly understood.…”

Carbonate mounds: From paradox to World Heritage

“…The other habitats not discussed in this paper are the deep coldwater coral colonies in canyons Huvenne et al, 2011Huvenne et al, , 2012. Perched under overhanging cliffs or high on rocky spurs in highly stressed environments, they form significant refuges, but again they are in general not in a position to develop to the giant build-ups further considered here.…”