Research is mobilized to stop the disappearance of corals

14% of the world's coral has disappeared has disappeared in less than ten years, according to a study conducted by a network of 300 researchers around the world.

This is a worrying figure for the health of our oceans: 14% of the world's coral disappeared between 2009 and 2018, or 11,700 km² of corals less over the entire globe. No region is spared  and in quantity, it is as if all the corals of the Caribbean and the Red Sea have disappeared. However, corals are home to a quarter of marine flora and fauna .

Global warming primarily responsible

The number one responsible is global warming: when the water temperature rises, the coral no longer recognizes the zooxanthellae, the micro-algae, with which it normally lives in symbiosis. So many algae that give it all its colors and provide it with 90% of its nutrients: the coral then starts to bleach and can then end up dying. As if, in short, he was dying of hunger.

As there are 1,200 different species of corals, several teams around the world are working to identify the most resistant corals. Swiss researchers, for example, have developed a calculation tool to identify the genetic families of corals that tolerate warming water better than others. Other researchers train corals to be less stressed by rising temperatures, gradually forcing them in aquariums to get used to warmer waters. They hope in this way to create an adaptive memory in new generations. There are also experiments to help more resistant coral species reproduce in aquariums, before attempting to implant them in disaster areas.

Some male and female corals release gametes into the water at a specific time of the year, giving birth to eggs and then larvae that settle on the bottom of the water to form corals. Coral can also reproduce by cuttings under very specific conditions of acidity and temperature.

Limit the damage

But these research nudges will simply limit the damage for 30 or 50 years, explains Serge Planes, research director at the CNRS. But that will not be enough. The urgency is obviously to fight against greenhouse gas emissions (according to the IPCC report on the oceans in 2019, 70% to 90% of the coral could disappear if the temperature increases by 1.5 ° C.). In this context, it is also urgent to protect corals from certain harmful human activities: overfishing and certain pollution, due to wastewater in tourist areas in particular.