First cases of coral bleaching reported in Gulf of Eilat
Worrying finding appears to upend long-held assumption that corals in the area are unusually resistant to rising seawater temperatures
Sue Surkes is The Times of Israel's environment reporter
The first examples of coral bleaching have been recorded in the Gulf of Eilat this year, following an unprecedented rise in seawater temperature, according to experts writing in the Israeli academic journal, “Ecology and Environment.”
The worrying finding comes after years of cautious reports that southern Israel’s world-renowned corals were bearing up under the challenges of climate change-related seawater temperature rises, and could serve as a reserve of coral material for reefs elsewhere in the world that have seen mass bleaching events.
While accounting for less than one percent of the earth’s surface, tropical coral reefs are home to at least 25% of known marine species.
Tourism in the city of Eilat is underpinned by its coral reefs.
Corals live in symbiosis with tiny algae, with the former providing room and board, while the latter supply food through photosynthesis.
When water temperatures rise above a critical threshold, the corals expel the algae, and their white skeletons become visible, hence the term, “bleaching.” Unless conditions revert rapidly, they eventually starve to death.
Data from a national program to monitor the Bay of Eilat show that the average daily maximum water temperature in August was 30.6 degrees Celsius (87 degrees Fahrenheit), compared to a multi-year average of 28.2 degrees Celsius (82.8 degrees Fahrenheit) for that month between 2007 and 2023. The average daily maximum temperature between July 12 and September 12 was 30.4 degrees Celsius (86.7 degrees Fahrenheit). On August 4, the mercury reached 31.9 degrees Celsius (89.4 degrees Fahrenheit).
Furthermore, winds were weak, and stagnant air prevented cooler layers of seawater from rising, leaving the upper layers uncharacteristically warm.
The first reports about bleaching, received on August 12, concerned the fire coral, Millepora dichotoma. In the following weeks, the phenomenon was observed in more than 10 coral species and in sea lilies, a type of marine invertebrate.
Marine scientists are currently researching the scope of bleaching and the rate of recovery and mortality, the article said.
“Although the resilience of the corals in the Gulf of Eilat is high and unique globally, it turns out that it too has a red line, and it is likely that the reef system has reached the threshold of a tipping point this year,” the article warned.
The writers said other conditions in the water, such as excessive nutrients from desalination plant brine and aquaculture, as well as traces of pharmaceutical residue in the corals themselves, exacerbated the effects of heat.
Around 26 tons of nitrogen are being dumped into the Gulf of Eilat annually, despite a 22-ton-per-year limit set by a Ministry of Environmental Protection committee of experts, the article said, and the government is under pressure to increase the amount even further.
Given that excessive stress could cause a sudden collapse of the coral reefs, the State of Israel is responsible for ensuring that such additional stress factors are minimized, the article concluded.
The US National Oceanic and Atmospheric Administration announced earlier this year that the world was experiencing the fourth global coral bleaching event on record and the second in the last 10 years.
The article in “Ecology and Environment,” published earlier this month (in Hebrew), was written by Asaf Zvuloni, an ecologist with the Israel Nature and Parks Authority, and two researchers from the Inter-University Institute of Marine Sciences in Eilat, Prof. Maoz Fein and Yonatan Shaked.
