Gulf of Eilat corals survive record heatwaves, offering global hope

Tel Aviv [Israel], September 18 (ANI/TPS): A new study has revealed that corals in the Gulf of Eilat have survived four consecutive and intensifying marine heatwaves, including the world's most extreme event in 2024, without experiencing mass bleaching -- a resilience unmatched anywhere else on the planet. The findings provide a rare glimmer of hope amid a global coral crisis, as reefs worldwide collapse under rising ocean temperatures.

Coral bleaching is a stress response that corals undergo when exposed to environmental changes, especially increases in water temperature. Corals have a symbiotic relationship with tiny algae called zooxanthellae that live inside their tissues. These algae give corals their beautiful colours and, more importantly, provide up to 90% of the energy corals need through photosynthesis.

However, when the water becomes too warm, corals become stressed and expel these algae. Without the algae, the coral tissue becomes transparent, exposing the white skeleton underneath, which is why the process is called "bleaching." The bleached corals look pale or completely white. Prolonged heat stress can eventually lead to coral death.

Led by PhD student Na'ama-Rose Kochman and Professor Maoz Fine of the Hebrew University's Institute of Life Sciences, in collaboration with the Interuniversity Institute for Marine Sciences in Eilat, the study highlights the Gulf of Eilat, also known as the Gulf of Aqaba, as a potential natural refuge for coral survival. The research was published this week in the peer-reviewed Science of the Total Environment.

"While nearly half of reef-building corals worldwide face the risk of extinction, our study shows that the Gulf of Aqaba remains one of the last strongholds of reef survival," Kochman said. "But even this refuge is not immune to the accelerating pace of climate change and local pollution."

The 2024 marine heatwave in the Gulf of Eilat lasted 113 days, with sea surface temperatures reaching 32.6°C -- 3.4°C above average -- generating 30 Degree Heating Weeks (DHWs), the highest thermal stress recorded globally last year.

Remarkably, five coral species endured the extreme temperatures without mass bleaching, the scientists said.

Researchers found that corals maintained stable energy reserves, with symbiont carbohydrates even higher during 2024 than in previous years. Different species displayed varied responses: Porites corals showed metabolic stability, while Cyphastrea experienced stress but recovered within months.

"These results highlight both the resilience and the fragility of coral ecosystems," Fine said. "They underscore the urgent need for regional conservation policies to safeguard what could be the world's last thriving coral reef."

Coral reefs are biodiversity hotspots, sustaining millions of human livelihoods through fisheries, tourism, and coastal protection. Yet marine heatwaves have become one of the leading causes of coral mortality worldwide.

Despite the Gulf's remarkable tolerance, scientists caution that sporadic shallow bleaching observed during recent summers suggests even this refuge may be approaching its ecological limits. The study stressed that without rapid global climate action and local protections against pollution and overfishing, the Gulf of Eilat's corals may eventually succumb to warming oceans.

"The Gulf of Aqaba provides a living model for understanding coral resilience," Kochman added. "Protecting it is not only a local responsibility but a global imperative." (ANI/TPS)

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