Scientists find that Hawaiian corals are surprisingly resilient to warming oceans

CORAL species in Hawaii could be more resilient than expected to rising temperatures and acidification of the oceans, according to a team of scientists who reproduced the living conditions of these reefs in lab conditions.

For 22 months, researchers from Oregon State University (USA) observed the resilience of three types of coral from four different sites in Hawaii to warmer and more acidic oceans. Four different tanks were set up, with water of varying degrees of warmth and acidity, in order to reproduce the living conditions of these reefs as closely as possible.

"Our tanks were outside under natural light and included pumps that simulated natural water flow. They were filled with seawater pumped in directly from a neighboring reef and included sand, rocks, fish, algae, crustaceans and other organisms in addition to corals," said in a statement Rowan McLachlan, the Oregon State University postdoctoral researcher, who led the study.

Published in Scientific Reports, the research explores the factors affecting coral health. According to the study, 61% of corals exposed to the warming conditions survived, compared to 92% exposed to current ocean temperatures. The two Porites species proved to be more resilient than M. capitata in the combined heating/acidification condition. Survival rates were 71% for P. compressa, 56% for P. lobata and 46% for M. capitata.

"Our study found that in the absence of local stressors such as nutrient pollution, overfishing, bottom trawling, physical damage from tourism, etc., at least half of Hawaiian reef corals will be able to survive and persist in up to 22 months exposure to ocean warming and acidification," says Rowan McLachlan.

"The results provide hope that if we can mitigate climate change and keep within the targets of the Paris Climate Agreement, coral reefs will persist in some form, albeit with reduced abundance and genotypic diversity," adds the researcher.

In January, an international exploration mission supported by UNESCO discovered corals submerged between 35 and 70 meters underwater, measuring 3 km long and 2 cm in diameter, located off the island of Tahiti. The reefs discovered were in perfect health.