Unique in the world, this coral reef, officially announced in 2016, was photographed and filmed thanks to two small submarines on January 30th, off the coast of Brazil. Onboard the Esperanza, 39 scientists from the NGO Greenpeace brought back the first images of this reef, which extends over 9,500 km², at the very place where the Amazon River and the Atlantic Ocean meet.
A site of great diversity
Long hidden from notice, this reef is concealed in brackish water loaded with sediments carried by the powerful Amazon River 200 km offshore. But for 40 years, scientists had suspected its existence: « the presence of reef fish, which live in coral habitats, had been observed in this area« , explains Edina Ifticene, Oceans Campaigner for Greenpeace. In 2010, a team of American and Brazilian researchers set out to map the seabed around the suspected area. The discovery was astounding, the team demonstrated the existence of a 1,000 km long reef located between 30 and 120 meters deep , between French Guiana and Brazil. Series of sampling campaigns followed between 2010 and 2014: there are indeed corals, sponges (about sixty species), calcified algae (rhodoliths), and fish (about 70 species) present in these muddy waters. These results were only revealed in April 2016 in the journal Science Advances.
With the images collected by Greenpeace, species from a very small area have already been identified: barrel sponges, soft coral, crustaceans, many fish, including two new species of butterflyfish, and even a manta ray!
Many mysteries…
But how can corals, which have a vital need for light, develop in such an environment? “ The reef is located in an area where corals are not supposed to develop ”, recalls Ronaldo Francini Filho, a researcher at the University of Paraiba in Brazil.
According to one hypothesis, » their presence in the midst of these brackish waters could be explained by a symbiosis with bacteria that reproduce through chemosynthesis. » This process allows, even without light, the production of organic matter from carbon dioxide and other mineral substances present in the water. « By studying how this reef develops in extreme conditions, we could understand how corals in stressful situations can adapt, for example, in case of ocean temperature changes, variation in salinity, or acidity of the water« , suggests Edina Ifticene.
…to protect
These still little-known corals are far from being preserved from all threats. Indeed, the Brazilian government has opened this region to oil explorations. The oil reserves in the region are estimated between 10 and 20 billion barrels (1 barrel equals 159 liters). The nearest site for an oil deposit could be « less than eight kilometers » from the reef according to Greenpeace. That’s why we must try to protect it. All these potential wells “ present risks of oil spill, increased by the strong currents in this ocean area ”, warns Edina Ifticene. « An oil leak would be catastrophic for the reef, but also for the mangrove at the Amazon’s mouth, almost impossible to clean.«
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