The treasure trove of biodiversity guarded by coral reefs has been revealed by the vast map of microorganisms that live there, so much so that many of them are close in diversity to those collected so far all over the world. This was discovered by the largest survey ever undertaken in the field, which led to the publication of as many as eight studies, in different journals, led by the French universities of the Sorbonne and the Cote d’Azur, the French center for genetics. Sequencing and American Rice University. The map will help protect these unique ecosystems, which are particularly threatened by the climate crisis, as their microscopic inhabitants are essential to keeping them healthy.
In the first study, published in Nature Communications, researchers led by Pierre Galland of the Sorbonne University collected 5,392 samples from three different coral species. The collection was conducted on 99 different reefs from 32 island systems in the Pacific Ocean between 2016 and 2018, as part of the schooner Tara expedition. The samples revealed 2.87 billion different genetic sequences, about 25% more than the 2.2 billion sequences reported by the Earth Microbiome Project, a project mapping global microbiome diversity.
The second of two major studies, led by Alice Rouen of the University of Côte d’Azur and published in the same journal, instead analyzed the relationship between changes in water temperature and the length of the ends of chromosomes, the so-called telomeres, which are a marker of health and aging. While the first corals studied proved to be more vulnerable to seasonal changes in temperature, the other showed high levels of stress only in the case of heat waves or particularly cold periods. This information is invaluable as it indicates that different coral reefs respond differently to climate change.
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