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Scientists use underwater speakers to encourage coral growth on degraded reefs

Woods Hole Oceanographic Institution biologists Nadège Aoki, left, and Aran Mooney install an underwater speaker system to broadcast healthy reef sounds off the coast of the U.S. Virgin Islands.
Dan Mele
/
Woods Hole Oceanographic Institution
Woods Hole Oceanographic Institution biologists Nadège Aoki, left, and Aran Mooney install an underwater speaker system to broadcast healthy reef sounds off the coast of the U.S. Virgin Islands.

You've heard of organ transplants, but what about the benefits of sound transplants? For coral reefs, an acoustic footprint called a soundscape is a critical indicator of their health.

The soundscape generated by a degraded reef in the U.S. Virgin Islands, for example, is less complex than that of a healthy reef — and its inhabitants.

Scientists at the Woods Hole Oceanographic Institution recorded the healthy reef complete with snapping shrimp, chirping parrotfish and whistling damselfish.

By playing the healthy reef sounds for the struggling reefs, they were able to recruit up to seven times more coral larvae.

The Conversation spoke to Nadège Aoki, the graduate student who led the new study, about this new technique. Her study was published in the journal Royal Society Open Science.

Environmental cues such as sunlight and sound tell larvae if an area is suitably hospitable.

"Healthier coral reefs tend to have very acoustically distinct signatures that differentiate from more degraded or impacted reefs. So on the healthy reef, you have this really distinct signature of a lot of complex fish aggregations that are producing those interesting grunts and burps and gurgles that you hear on the sound files. And on impacted reefs, you have some of those same sounds, but it's much quieter, and there's much less of it," Aoki said.

She said scientists know that coral larvae are sensitive to sound, but the physiological mechanism is still under investigation.

"They actually have ciliated hairs on their body. So they have lots and lots of little hairs around the edge of their epidermis, and some scientists hypothesize that deflections of those hairs might be a mechanism for how they sense sound — the same way that we have hair cells in our ears that help us to hear," Aoki told HPR.

Aoki said the team hopes to use the artificial soundscape approach to help other coral species besides Porites astreoides.

"I definitely would not say that this is a silver bullet for the tons of problems that are facing reefs, particularly anthropogenic warming, but it is nice to feel like we've added another tool to our toolkit in restoration and protection of our reefs."


YouTube video courtesy of the Sensory Ecology and Bioacoustics Lab at the Woods Hole Oceanographic Institution, with support from the National Park Service in the U.S. Virgin Islands.

This story aired on The Conversation on March 14, 2024. The Conversation airs weekdays at 11 a.m. on HPR-1. Sophia McCullough adapted this story for the web.

Maddie Bender is the executive producer of The Conversation. She also provided production assistance on HPR's "This Is Our Hawaiʻi" podcast. Contact her at mbender@hawaiipublicradio.org.
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