Tuesday, March 5, 2024
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For the love of corals

THE WASHINGTON POST – Covering coral nurseries with shade. Spreading a manufactured fog over the surface of the ocean. Feeding threatened corals and dosing them with probiotics.

These are just some of the inventive ideas scientists are floating amid an urgent scramble to protect corals from rapid ocean warming that has sent water temperatures in many places around the world climbing to record highs.

A blistering marine heat wave caused extensive coral bleaching off the coast of South Florida. And similarly damaging conditions have been projected to hit much of the Caribbean, according to the National Oceanic and Atmospheric Administration.

“An existing coral is worth a lot more than a new coral that you put in the water, so if you can keep them, that’s the best thing to do,” said executive director of strategy and development at the Australian Institute of Marine Science David Mead who has researched bleaching interventions.

These ideas, expert said, are a small part of any overall solution to saving imperiled reefs.

A school of fish swim through a break in the coral along the Great Barrier Reef in Australia. PHOTO: THE WASHINGTON POST


Exposure to the sun’s rays and too much heat for too long can trigger bleaching – when corals expel the beneficial plantlike organisms called zooxanthellae that live in them, causing them to lose their vibrant color and turn a deathly white. Using shade to lessen the amount of light hitting heat-stressed corals can help.

Some research suggests that high levels of direct shading using a specially designed cloth could reduce the stress placed on corals, said a research scientist at the Australian Institute of Marine Science Neal Cantin. Tests found that 30 or 50 per cent shading could be effective, said Cantin, who spoke during a recent webinar on strategies to address the ongoing bleaching event hosted by the Coral Restoration Consortium, a global group of experts.

Direct shade is most important during the middle of the day between 10am and 3pm, particularly when the water is calm, he said.


Covering the surface of the ocean with fog, also known as fogging, is another method of shading that’s being explored, Mead said. The type of mist researchers are trying to produce is similar to natural sea fog, he said.

“You can create a fog at the right sort of density so that it reduces light,” he said.

While fogging isn’t suitable for use at a very large scale, it could cover more area than standard shade structures, he said. He noted that shade cloth could be limited to around tens to hundreds of square meters, whereas fogging could cover around 10,000 square metres.


Work is underway to develop probiotics that can be given to corals to help them better endure hotter temperatures, said Tali Vardi, executive director of the Coral Restoration Consortium, the global group of experts.

“It’s kind of like when you’re sick and you go to get a smoothie with immunity boosters and bee pollen and whatever else,” Vardi said.

In the meantime, scientists are also trying to support heat-stressed corals with more food through a process known as supplemental feeding.


Researchers are also looking into methods to actively cool the water around corals.

One way involves trying to move cooler water from a nearby location and mixing it with the warm water to lower the overall temperature.

While Mead said he has “yet to see any maths where this method works”, it could make some difference if used in small areas where the water isn’t moving much. A strong current would just carry the cooler water away, he noted. – Allyson Chiu