The corals of the Red Sea, in the Gulf of Aqaba, are particularly resistant to high temperatures. The researchers wanted to better understand this phenomenon. The result of their investigations was published on May 3, 2021 in the journal PNAS.
Exposure to high temperatures
Due to rising temperatures in the oceans, symbiotic algae, which give corals their color and nutrients, are being squeezed out of coral structures. This results in a phenomenon called bleaching: corals change at the same time as they weaken. But the corals of Aqaba Bay are particularly resilient. To better understand the molecular mechanism behind this robustness, the team from the Ecole Polytechnique Fédérale de Lausanne (Switzerland) subjected these organisms to different temperatures, especially those that will unfortunately be felt in the coming decades. “Although the average monthly maximum water temperature in this area is around 27 degrees, the corals were exposed to heats of 29.5 ° C, 32 ° C and 34.5 ° C. Short-term, for 3 hours, and long-term, for a week“, the school points out in a press release. In parallel, the researchers measured the expression of coral genes, but also symbiotic algae.
Sheltered for 100 or even 200 years
The obtained results show that corals and their algae can withstand average temperatures 5 ° C higher than normal. “The main finding is that we realized that these corals still live well below the tolerance threshold that their molecular mechanism can withstand, which protects them from rising temperatures over 100 or even 200 years sums up in a press release Romain Savary, lead author of this new study. In any case, up to 32 ° C we were able to measure that they are recovering without molecular consequences and that they are acclimatizing for a short as well as a long period of heat, as well as their symbiotic partners.In fact, the rise in temperature in the Red Sea is not expected to exceed 5 ° C by the end of the century.
The key to the resistance of these corals lies in the level of gene expression. “It’s a real concert of genetic expression that gives this super power to corals.“, notes Anders Meibom, director of the Laboratory of Biological Geochemistry at EPFL. This genetic expression is now a reference for the scientific community that will now have a way to identify these” supercorals “as scientists call them. However, these organisms, no matter how resistant, they represent a miraculous solution to protect all the coral reefs on the planet in particular A large coral reef experiencing repeated episodes of bleaching. “Coral is extremely dependent on its environment and in general only long natural colonization would allow it to adapt elsewhere. In addition, the Great Barrier Reef is the size of Italy, it is impossible to plant it artificially.“, recalls Anders Meibom. Only spontaneous recolonization of areas weakened by rising temperatures is possible. But the protection of the Red Sea corals, in order to maintain a healthy supply of robust organisms, remains particularly important so that one day is not noticed.