Climate ChangeEnvironment

Coral disease will affect 3 out of 4 colonies by 2100

Bacteria and fungi can more easily infect corals due to increased sea temperatures

(sustainabilityenvironment.com) – A black band composed of cyanobacteria, sulfide-oxidizing bacteria and sulfate-reducing agents. Or a yellow band that signals the killing of algae living in symbiosis with coral colonies. The fate of corals isn’t just bleaching. The climate crisis is making them sick more and more, facilitating the work of pathogens such as fungi and bacteria that infect the reefs. Only in the last quarter of a century, the spread of coral disease has tripled.

This was calculated by a study published in Ecology Letters that conducted a meta-analysis of the existing literature on the subject, 108 studies on changes in time of global coral disease. That the authors, researchers of New South Wales University, have analyzed in relation to the temperature, expressed using the average summer temperature of the sea surface, and cumulative thermal stress calculated as weekly anomalies of sea surface temperature.

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At the end of the 25 years covered by the literature, coral diseases affected 9.92% of the colonies. A value three times higher. And if we continue to generate greenhouse gases at today’s pace, that is, in an emissive business as usual scenario, this percentage could rise to over 75% by the end of the century. A devastating impact, which crosses and is added to that of coral bleaching, the whitening caused by prolonged exposure to excessive thermal stress due to extreme and lasting heat waves.

Coral disease is a serious cause of global coral mortality and coral reef decline, and our models predict that it will continue to worsen, although ocean temperatures will remain conservative,” explains the lead author of the study, Samantha Burke.

The impact will not be the same everywhere. According to current data, the situation will worsen especially in the Pacific Ocean, less in the Atlantic Ocean and the Indian Ocean. “Some oceans in particular are more at risk, but it is difficult for us to know whether this is due solely to warming ocean temperatures or whether it is combined with the many other stressors that corals face,” Burke points out.

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