This is a new alert for the survival of corals. According to the United States National Oceanic and Atmospheric Observation Agency, the world is currently experiencing a massive episode of coral bleaching, which threatens their survival. This phenomenon is accelerating as the oceans warm up and concerns all coral massifs on the planet.
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Australia, with its Great Barrier Reef, but also the Caribbean, the Red Sea and the Pacific: waters around the world are currently affected, for the second time in ten years, by a massive episode of coral bleaching due to record ocean temperatures, warned Monday April 16 the United States National Oceanic and Atmospheric Observation Agency. This decline phenomenon threatens the survival of coral reefs around the world.
“ As oceans continue to warm, coral bleaching becomes more frequent and severe said Derek Manzello, coordinator of NOAA’s Coral Reef Observatory. This is the 4th phenomenon of such magnitude since 1985. The latter is getting worse with the record warming of the oceans. While 30 to 50% of the planet’s corals have already been lost, scientists point out that, without major change, they could completely disappear by the end of the century.
This very serious threat would have multiple consequences on ocean ecosystems, but also on human populations, impacting their food security and local economies, particularly tourism.
850 million people depend on these reefs
According to WWF, the global fund for nature, 850 million people around the world depend on these reefs for their food, their employment or for the protection of coastlines against swells or tsunamis. The survival of part of humanity therefore depends on the reduction of thermal stress which causes coral bleaching.
Corals also play an important role in marine ecosystems, with more than a quarter of marine species having taken up residence there. Coral reefs thus constitute “ a visual, contemporary example of what is at stake with every fraction of a degree of warming », underlines Pepe Clarke of the WWF.
NOAA, however, declared that it had carried out “ significant progress » in the development of techniques against coral bleaching. These latter constitute in particular “ moving coral nurseries to deeper, cooler waters » or install shade to protect corals from the sun’s rays in other areas.
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Bleaching linked to increased water temperature
Coral colonies are made up of tiny creatures called polyps, which secrete a limestone exoskeleton. Heat waves kill animals either simply by excess heat, or by ejecting from their bodies the algae that provide them with nutrients: this is coral bleaching.
“ The scale and severity of mass coral bleaching is clear evidence of the harmful effects of climate change today », Estimated Pepe Clarke, of the environmental NGO WWF. The temperature of the oceans, which play a key role in regulating the global climate, has reached a new absolute record in Marchwith an average of 21.07°C measured on the surface, excluding areas near the poles, according to the European Copernicus Observatory.
Linked to the increase in water temperature, this process, which results in discoloration, can lead to the death of these living organisms in the event of prolonged or severe exposure to thermal stress. But the phenomenon can be reversible: affected corals can survive if temperatures drop and other stress factors, such as overfishing or pollution, are reduced.
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