EILAT, Israel — Rugged red mountains tower over the aquamarine waters off Eilat in southern Israel. A group of divers plunges beneath the waves on a warm winter morning, bound for a crag encrusted with coral known as Japanese Gardens. The hypnotic reverie of the undersea world shatters with the shock of spotting a bone-white colony.

Scientists have long considered the corals in the Gulf of Aqaba to be uniquely resilient to extreme temperatures, and have taken to calling them “supercorals.” Bleaching had never before been documented here. For the first time on record, however, last summer’s record-smashing heat wave brought these corals to “the threshold we’ve been talking about all along,” Maoz Fine, a Hebrew University of Jerusalem professor studying coral resilience and one of the leading Israeli scientists monitoring the gulf ecosystem, told Mongabay. He and his colleagues first received reports of bleached corals in August 2024 and are now studying the episode’s severity and extent.

“There’s no doubt that we need to wake up, because climate change is having an impact — here all the more so,” he said.

Coral reef ecosystems are likened to submarine rainforests: diversity of life in stupefying abundance. As oceans warm due to human-caused climate change, corals — colonies of jellyfish-like animals called cnidarians — eject the photosynthetic zooxanthellae that live symbiotically within their cells, and turn a ghastly white. While not a death sentence, the weakened corals, which form a cornerstone of nutrient-poor tropical ecosystems, are left highly vulnerable. Many die.

Scientists have long considered this arm of the Red Sea, home to some of the northernmost coral reefs in the world, a refuge against the ravages of climate change. Researchers studying these corals proposed they migrated northward through the Red Sea after the last Ice Age, around 8,000 years ago. The hotter waters of the Bab el Mandab strait, at the sea’s southern end, selected for heat-resilient corals. Their offspring settled in the comparatively cooler waters of the Gulf of Aqaba, an area shared by Israel, Jordan, Egypt and Saudi Arabia.

Over the Northern Hemisphere summer of 2024, the reefs that cover huge swaths of these waters suffered an unprecedented assault: the most intense heat wave on record. Fine estimated that only perhaps 5% of the corals in the area of the gulf off Eilat bleached during the oppressive summer. A small fraction of the bleached corals died, but most recovered over the relatively cooler months that followed. This, Fine said, is a testament to their exceptionally high temperature resilience.

He and his team published their preliminary findings in the Hebrew-language journal Ecology & Environment in November; a detailed report in a peer-reviewed journal is forthcoming.

“The conditions here were the most extreme, both in terms of duration and intensity. It was the strongest heat wave we’ve experienced here, and the strongest in the world in 2024 was here,” Fine said.

‘Off the charts’ temperatures

Last year, the U.S. National Oceanic and Atmospheric Administration (NOAA) said the world was experiencing the fourth global coral bleaching event on record, with heat stress “extensive across the Atlantic, Pacific and Indian Ocean basins.”

Konrad Hughen, a marine chemistry researcher at the Woods Hole Oceanographic Institution in Massachusetts, U.S., told Mongabay global air and water temperature trends were “off the charts,” and increasing at rates that “are getting worse faster.”

“Coral reefs are very much a legitimate canary in the coal mine for the globe in terms of ecosystem responses to global warming,” Hughen said.

In addition to his position at Hebrew University of Jerusalem, Fine heads the Laboratory for Coral Reef Ecology at Eilat’s Interuniversity Institute of Marine Science, a beachside research facility south of the town’s resorts, port and coral nature reserve.

Below his office window stands a bank of tanks, pipes and sensors dubbed the Red Sea Simulator. Coral samples from the reefs bask in the winter sunshine. Researchers can test how variables such as acidity, nutrients, temperature and pollution affect the health and life cycle of different species in real time. Just offshore, a few meters down, Fine and his colleagues run a coral nursery, where a cluster of equipment transmits data via a to the internet.

Naama-Rose Kochman, a doctoral researcher at Hebrew University who works in Fine’s lab, conducted a series of experiments exposing one of the most common corals found in the gulf — Stylophora pistillata, which she calls “our lab rat” — to increasing water temperatures.

“Only above 33°C [91.4° Fahrenheit], which is six degrees above the summer temperature they are exposed to here, did they start bleaching, followed by mortality,” she said.

Coral researchers gauge the accumulation of heat stress in terms of “degree heating weeks”: a measure of how much in excess of the average high temperatures have been and for how long, during a given 12-week period. The benchmark for a risk of bleaching is 4°C-weeks, while 16°C-weeks spells a risk of severe coral mortality, according to NOAA. Temperatures in the Gulf of Aqaba clocked in at nearly eight times the bleaching threshold: 30°C-weeks over the summer of 2024.

“Conditions like these anywhere else would cause total mortality to any reef,” Fine said.

Instances of coral bleaching also emerged on the Jordanian side of the gulf, 5 kilometers (3 miles) from Eilat, but Jordanian authorities have kiboshed publication of reports on the matter, according to a Jordanian scientist who spoke on condition of anonymity out of concern for their job.

“Our corals are unique and we have the last coral refuge in the world,” the scientist told Mongabay, adding they were crestfallen at the reports of coral bleaching. “But at the same time, this should be a lesson and should give encouragement for researchers and authorities to collaborate and to start new projects and initiatives to save corals.”

The other threat: Pollution

Despite the corals’ rebound after this summer’s unprecedented bleaching event, alarm bells are ringing. This area of the northern Red Sea is projected to experience an increase in the frequency and intensity of heat waves like the one last summer. That bodes ill for the future of this natural wonder.

The best chance for preserving the corals’ long-term health entails limiting other factors that could reduce their ability to withstand extreme heat. Sick corals struggle to resist high heat, and the foremost threat is water pollution.

“If we want to successfully preserve the high resilience corals have here … we need to reduce as much as possible the local stressors,” Assaf Zvuloni, a marine ecologist with the Israel Nature and Parks Authority, told Mongabay.

One of the main pollution threats facing these coral ecosystems, the Europe-Asia Pipeline Company (EAPC) terminal, sits barely half a kilometer from Eilat’s Coral Beach Nature Reserve. Its rust-colored jetties jut into the blue sea. EAPC imports oil that gets pumped 254 km (158 mi) to the city of Ashkelon on the Mediterranean, bypassing the Suez Canal. That pipeline burst in 2014, spilling an estimated 5 million liters (1.3 million gallons) of crude into the desert north of Eilat. The spill caused an estimated 281 million shekels ($78 million) in damage, according to Israel’s Ministry of Environmental Protection.

EAPC struck a deal with an Emirati company in 2020 to increase oil shipments to Europe through that pipeline. Environmentalists have warned that a significant spill could wreak havoc on the reefs, and in 2021, the ministry instituted a “zero-added-risk” policy that effectively halted additional oil shipments to Eilat, capping imports at 2 million tons annually.

To the dismay of environmental groups, scientists and Eilat’s mayor, Prime Minister Benjamin Netanyahu’s government overturned that decision in December, effectively allowing unfettered oil imports despite the potential risk to the reefs.

Fine said the pipeline poses an “enormous risk” and “immediate threat” to the coral ecosystems in the Gulf of Aqaba and called for its discontinuation.

When coral reefs vanish, the ecosystem they sustain follows, affecting human populations dependent upon them for food or tourism. Egypt leads the world in coral reef tourism, bringing in about $7 billion in revenue annually, according to figures from the High Level Panel for a Sustainable Ocean Economy. That’s about half of tourism’s 8% contribution to Egypt’s GDP. The economies of Eilat and the neighboring Jordanian city of Aqaba are also heavily dependent on visitors drawn to the area’s coral.

“There’s regional interest in protecting it, and the significance is global,” Fine said. He advocates for the establishment of a World Heritage Site shared by the four countries abutting the gulf as “the only way to protect these reefs.”

“Doing it together is the most logical way, and I think it’s possible.”

Banner image: Maoz Fine and Naama-Rose Kochman visit the lab’s coral nursery and monitoring station near Eilat. Image by Ilan Ben Zion for Mongabay. 

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