Australia's Great Barrier Reef, a world heritage gem of humanity, suffered a "catastrophic" hecatomb of its corals during a heated heat wave in 2016, threatening a greater diversity of marine life than hitherto estimated , warns study Thursday.
About 30% of the corals of the vast ensemble died during the heat wave between March and November 2016, the first episode of two consecutive years of bleaching.
Listed as a UNESCO World Heritage Site in 1981, the reef extends over approximately 348,000 square kilometers along the Australian coast and is the largest coral reef in the world.
Based on published survey by the scientific journal Nature, coral, which is home to other marine creatures, has been hard hit by the rise in water temperatures following global warming.
Terry Hughes, co-author of the study and director of the Center of Excellence for Coral Reef Studies at James Cook University, told AFP that the most endangered species are branch corals such as coral reefs that provide hiding places for juvenile fish.
The corals most likely to hold the shock are smooth, melon-shaped, pursued the researcher. These corals do not have too much trouble building their skeleton but "they are not very useful for habitat," adds Hugues.
During the bleaching of 2016, corals from the northern part of the Great barrier suffered a wave of "catastrophic deaths," the study continues.
"This coral dieback has caused radical changes in species diversity in hundreds of individual reefs, where mature and diverse reef communities are turning into more degraded systems, where only a few enduring species survive," writes Andrew Baird, other scientist
Bleaching is a phenomenon of withering which results in a discoloration of corals. Under the pressure of factors such as warming, stressed corals expel the algae with which they have a symbiotic relationship, and give them color and energy.
The study calls for the protection of surviving corals, estimated at about one billion .
"These are the ones who will recharge and re-inhabit altered reefs," says Hugues, adding that water quality needs to be improved by reducing coastal pollution.
to limit global warming as in the Paris agreement are also crucial.
"We had four bleaching episodes (1998, 2002, 2016 and 2017) on the Great Barrier with an overall temperature rise of 1 ° C," says Hugues. "If we continue with our emissions as if nothing had happened, I do not think the Barrier will survive it."
Reefs cover less than 0.2% of the ocean surface but are home to 30% of animal species and marine plants, protecting them from predators and serving as their pantry. They contribute to coastal protection, human nutrition, and tourism.