ARDECO

Like tropical coral reefs, cold-water coral reefs form complex habitats that support local biodiversity and biomass while fixing carbon dioxide in their skeleton. These corals thus provide important ecosystem services. Although they grow several hundred to thousands of meters below the surface, these corals are not spared from human pressures. Deep-sea trawling, chemical contamination and accumulation of plastic waste are all threats to the health of cold-water corals, in addition to ocean warming and acidification. Warming will push corals into deeper and colder waters, while acidification will push them into shallower, more carbonate-rich waters. The two phenomena combined could significantly reduce their fundamental niche if they are not able to adapt.

The objective of the ARDECO project will be to evaluate the adaptive capacities of the three main species of deep reef building scleractinians (Desmophylum pertusum, Madrepora oculata and Solenosmilia variablis) in the face of global climate change. The corals will be experimentally subjected to a temperature increase and/or a pH reduction for a period of 6 months in order to test their response to global change scenarios for the year 2100. The great originality of these experiments will be to carry them out by simulating the depth where these species naturally live, thanks to pressurized aquariums developed specifically within the framework of ARDECO. Simulating hydrostatic pressure is indeed fundamental to evaluate the response of deep-sea corals to global changes for two reasons: i) because carbonate dissolution increases with hydrostatic pressure, thus strenghtening the effects of acidification, and ii) because pressure influences the physiological state of living organisms and neglecting it may induce an experimental bias. The response of corals to changes in their environment will be assessed by measuring their nutrition, growth, reproduction, behavior, and the nature and function of interactions between coral polyps and their microbiome. The second innovative aspect of ARDECO will be to understand the response of the coral holobiont to changes in its environment.