The Benthic Communities of Condor Seamount

Poster presentation at ATLAS 3rd General Assembly.

Seamounts have long been regarded as specialized habitats that support unique benthic communities, generally more diverse and species rich than continental slopes of similar depths. Some of the structural species commonly observed in these habitats include cold-water coral reefs, coral gardens and sponge grounds, which find in these offshore features suitable substrates and increased food supply to fully develop. The functional role of these communities in enhancing local biodiversity rates by providing shelter and refuge to a set of accompanying species makes them ecologically important for conservation, and some them are currently included in the list of Vulnerable Marine Ecosystems (VMEs). Despite their key role in maintaining global ocean biodiversity and fluxes, some aspects of their ecology still remain unknown. Commercial fisheries, mostly bottom trawling and long-line fishing, have historically targeted offshore seamounts, producing detrimental, usually long-lasting, effects in the structure and composition of these communities. The ecological characterization of seamounts is of key interest to generate robust scientific knowledge to promote its protection from deleterious human activities.

Condor seamount, located only 17 km away from Faial Island (Azores), was recently declared a MPA as part of the Azores Marine Park, and fishing activities were prohibited in 2010. This setting provides a unique opportunity to understand the ecology and the capacity of recovery of benthic communities dwelling in a seamount that has historically been affected by commercial long-line fishing but it is currently protected from their negative impacts. As part of the MIDAS cruise in 2016, a set of ROV and tow-cam video transects were performed on the summit and on both flanks of the seamount, at depths between 250 and 1100 meters. The video images recorded have given us the possibility to comprehensively characterize its key faunistic associations using fine-scale quantitative data. The information on structural species will also be used to determine what constitutes a VME, and will provide clues on the spatial distribution of such aggregations in offshore seamounts.

In general terms, associations of large gorgonians dominate the consolidated substrates of the summit (e.g. Viminella flagellum, Dentomuricea aff. meteor and Callogorgia sp.), whilst sponge grounds are a common feature of the flanks (e.g. Pheronema carpenteri) and the gorgonian Candidella cf. imbricata dominates the deepest areas. The information gathered form the MIDAS cruise will be used to define the baseline condition of Condor seamount at the time fishing activities ceased and set the basis to determine the evolution of benthic communities in absence of fishing activities.