// NATURE NEWS — SPAZIO & SCIENZA
The super El Niño is cooking coral reefs — can lullabies and probiotics save them?
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Coral reefs in the Philippines are still recovering from the last El Niño, even as another one gains strength. Credit: Alex Mustard/Nature Picture Library
It’s peak spawning time for coral in the Caribbean Sea and there’s something new in the water this year. Underwater speakers at several locations are serenading clouds of floating larvae as they search for a place on the reef to permanently settle. Sounds recorded at vibrant reefs — such as the clicks of snapping prawn and the thrum of fish — fill the water at spots where coral reefs are struggling because of high temperatures, pollution and other stresses.
This El Niño is set to be the largest on record by a ‘mind-blowing margin’
The hope is that these sea songs will lure floating coral larvae into settling on the degraded reefs and help them to recover. This project, run by researchers at the Woods Hole Oceanographic Institution (WHOI) in Massachusetts, relies on the discovery that coral larvae can sense sound and use it as a cue to follow as they search for a permanent home1.
“Healthy reefs are naturally broadcasting sound all over the place,” says Aran Mooney, a marine bioacoustician at WHOI who leads the project. He’s part of a small army of researchers stepping up their efforts to save threatened corals. In addition to playing lullabies to restore damaged reefs, they are implementing other emergency measures, such as moving corals from shallow locations to deeper, cooler water and inoculating reefs with protective microorganisms.
The planet’s corals need all the help that they can get. This year’s record-breaking ocean temperatures, resulting from human-caused climate change and a super-strong El Niño brewing in the Pacific Ocean, have spurred fresh alarm about the future of coral reefs. Elevated water temperatures can cause coral bleaching, which happens when the usually richly coloured organisms expel the symbiotic algae that they rely on for nutrients; this can ultimately kill the coral.
Researchers test a system in Dominica that plays sounds of a healthy reef to help corals grow.Credit: Dan Mele, ©Woods Hole Oceanographic Institution
As of late August, coral bleaching had been observed in corals around Florida, the Pacific coast of Panama and Kiribati in the Central Pacific. The Coral Reef Watch of the US National Oceanic and Atmospheric Administration found that, in large swathes of the oceans, the water had reached temperatures that placed corals at risk of bleaching and heat mortality. Temperatures are expected to rise even further in 2027 as the El Niño reaches its full strength, and that will raise the risks for corals.
Coral reefs can recover from bleaching and their ability to bounce back has often surprised scientists. But recovery takes time and corals can’t catch a break: this year’s bleaching event comes less than a year after the last global one ended in 2025.