On Wednesday at dawn, scientists, sailors and technicians from the ChEReef 2022 (Characterization and Ecology of cold-water coral Reefs) campaign brought back these animals after fifteen days at sea, taken from a canyon classified Natura 2000 located 800 meters deep and 12 hours of navigation from the mainland in the Bay of Biscay.
“The impact of climate change on the growth of these corals” will be studied at Océanopolis as part of the Ardeco project, develops Dominique Barthélémy, curator in charge of the living environment in this national center for scientific culture dedicated to the implanted ocean. in Brest.
These “madrepora oculata” corals will be kept under pressure in equipment called Abyss box, he points out.
“Cold-water corals have an important functional role for the whole deep system because many species come to feed there, and they are carbon sinks”, explains Lenaick Menot, researcher in benthic ecology (the study of the bottom of the oceans) at Ifremer and co-head of the campaign.
“They are threatened by fishing (bottom trawling editor’s note) and probably by climate change” he worries.
Their scientific value is matched only by the extraordinary precaution with which the staff unloads the fifteen buckets containing the corals.
– CO2 acidifies the seas –
Subject to the warming and acidification of the ocean, “corals will probably be the first to suffer” according to the scientist.
“The ocean is a trap for atmospheric CO2 which acidifies seawater, and prevents corals from secreting their calcareous skeleton” which also tends to dissolve.
To read the future of corals, the first step was to imagine a sampling operation at 1,000 meters deep, and bring them to the surface while maintaining the pressure and temperature of their original environment.
For this, Ifremer used the Victor submarine, a jewel of technology weighing nearly 5 tons that can descend to 6,000 meters.
“The most complicated thing was to fight against the current and make sure that the ballast and the cables didn’t rub on the cliff,” recalls Luc Tailliez, one of Victor’s pilots and technical manager.
Able to withstand 600 bars of pressure (i.e. 600 kg per square centimeter), it is piloted from the surface by two technicians connected to the submarine by a cable.
The mechanical arms of the robot, operated remotely using cameras, grabbed the corals to place them in small pressurized aquariums placed in a basket, in order to keep the corals at 100 bars and 10 degrees whatever the external conditions. .
A world first.
– Survival threatened –
Sheltered in the Océanopolis, the corals will be taken from cuttings to be placed in pressurized boxes the size of a small fire extinguisher, also reproducing the current and the food to which they are accustomed.
“One of these boxes will be on display to the public” assures Dominique Barthélémy, who specifies that “this is part of the public awareness missions of the Océanopolis which wishes to encourage its visitors to better protect the environment”.
Mr. Menot concludes: “We will subject them to two climate change scenarios, a temperature increase of two degrees, an acidification of the water by 0.2 units, which the IPCC models predict by 2100. If they are to dive to find the cold water they need, their survival is probably threatened by global warming”.
