Published on January 31 in the journal Frontiers in Marine Science, a study conducted by 17 researchers (including 2 from Ifremer) of 8 different nationalities from the international network for study and scientific exchange on submarine canyons (INCISE formed since 2012) highlighted the ecological importance of these unique environments. It emphasizes the need to protect them from human activities to preserve the fragile life thriving there.The biological role of canyonsCurrently, nearly 10,000 submarine canyons have been identified worldwide, including 300 in the Bay of Biscay, which extends from Brittany to the Basque Country. This type of geological formation is also found in the Mediterranean Sea near the coasts.
These vast deep valleys (often more than 2,000 meters deep) and steep, provide a refuge, habitat, reproduction, and nursery site for many little-known species (cold-water corals, fish, crustaceans, etc.). It is the interaction between the diverse topography of canyons, allowing different ecological niches for species, and ocean currents that influences the functioning and dynamics of the communities living in open water and on the seabed. When these currents collide with the canyon reliefs, they deposit nutrients (mineral salts, organic matter…) that form the base of a complex food chain in the depths, thus ensuring the survival of the animals thriving there.
It was recently proven that the submarine canyons of the Bay of Biscay are real refuges for cold-water corals (about 60 different species identified and mapped). During her thesis at Ifremer, Inge Van den Beld, co-author of the study, demonstrated that these corals form reefs or gardens, and » lined end to end, all the observed coral habitats in the Bay of Biscay […] represent 48 km in length « , explains Lénaick Menot, co-author of the study and researcher at the Deep Environment Laboratory of the Ifremer center in Brittany at Brest, who supervised this thesis.
Various anthropogenic pressures
« Overall, the pressures exerted by human activities include waste, fishing, the dumping of terrestrial mining residues, and the extraction of oil and gas « , notes Lénaick Menot. The effects of climate change can also decrease or increase the intensity of currents in the canyons, which will impact the structure and functioning of marine fauna in general as well as the nutrient supply to the deep-sea ecosystem. Hence the need for tighter protection of these essential deep habitats.Towards better protection
« Only 10% of the identified canyons in the world are located within marine protected areas […]”, specifies Florence Sanchez, co-author of the study and engineer at Ifremer, at the Arcachon Resource Environment Laboratory. Even if this figure remains low, the study reveals several examples of successful accomplishments in protection and management measures for certain submarine canyons. » Our study not only identifies the ecological significance of canyons but also highlights the need for a better understanding of the anthropogenic impacts on the ecosystems that submarine canyons harbor « , explains Ulla Fernandez-Arcaya, the principal author of the study and researcher at the Balearic Oceanographic Center in Spain.
These vulnerable habitats are not yet subject to preservation measures, but the research conducted by Ifremer has fed into the recommendations of the National Museum of Natural History. The goal of this project is the designation of a Natura 2000 network (which is a European network) for the offshore reef habitat, as part of the European directive « Habitat, Fauna, Flora« . In 2014, eight major sectors were thus defined, including 15 canyons along the French Atlantic facade.
Morgane Constantin
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