A surface coral "refugee" in depth

On April 4, 2019, in the archipelago of Gambier, in French Polynesia, Ghislain Bardout, co-founder of the expeditions Under The Pole, and two divers of his team put together a coral, Leptoseris hawaiiensis, found set at the unexpected depth of 172 meters deep. Usually, this coral lives at a moderately lit depth (hence the term mesophotic), between 30 and 40 m deep.

" It's a world record, an exceptional discovery Bernard Salvat, honorary professor, founder of the Center for Insular Research and Observatory of the Environment (Criobe, laboratory of excellence CNRS-University of Perpignan-EPHE).

The biologists of Criobe, Laetitia Hédouin, Michel Pichon and Héloïse Rouzé were able to identify the species. " This discovery helps to support the hypothesis of a "refuge zone" for surface corals in the depths of the ocean and a hope to restore them "Say Ghislan Bardout and Emmanuelle Périé-Bardout.

A discovery expected for 40 years

" I've been waiting for such discoveries for 40 years, says Michel Pichon, attached to the Museum of Tropical Queensland Townsville and specialist in coral reefs. The total harvest of 4,000 samples represents the world's largest collection of mesophotic corals, especially at depths greater than 90 meters. "

Confirmation of Great Barrier Reef Decline in 2016

" These results provide a robust and indispensable basis for testing hypotheses concerning the ability of mesophotic coral environments to serve as a refuge, after the degradation of shallow reefs, affected by global changes and their role in re-seeding degraded reefs. ", Says Michel Pichon.

Laetitia Hédouin, a coral biologist (CNRS), agrees. " It will never be possible to talk about coral reefs without considering this life in the depths as a "liferaft" for surface reefs She says.

A new vision of the coral ecosystem

These discoveries reveal a totally new vision on the functioning of coral reefs. They constitute a continuum of the surface to the mesophotic zones where the coral communities succeed one another. " Our knowledge suggested that 25% of corals could descend from the surface to the depths and today, after more than 4,000 samples collected, the trend is reversed, with more than 60% of surface species capable of colonizing the depths. "

The sailboat Tara completes her tour of the Pacific corals

The expedition will continue for another three months. Then the DNA analyzes of the samples will take place in both Mooréa and Perpignan. The main scientific results should be presented at the International Congress on Coral Reefs in July 2020 in Bremen, one of the world's leading marine research centers.

By highlighting a largely unknown part of coral reefs, researchers hope to contribute to the implementation of appropriate management and protection measures to safeguard these reefs.

. (TagsToTranslate) biodiversity (t) Environment (t) depth (t) refugee (t) face (t) coral

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