Soundtrack of the sea: divers use underwater speakers to help dying coral reefs

However, the tools a team of divers are carrying to the seafloor are not what you would expect to find in a marine biologist’s kit. They are installing waterproof speakers at the bottom of the ocean, and the man leading the team is not a scientist.

“It’s very different from everything I did before,” says Marco Barotti, an artist from Italy.

Five years ago, Barotti began creating sculptures based on 3D scans of coral. He was inspired by emerging research suggesting that sound could be the key to reviving struggling reefs. “Sound has always been at the core of my work but never at this level,” he explains.

The soundtrack of the sea

To the human ear, the underwater world might seem pretty quiet, but a healthy reef is actually a cacophony of noise. It’s a biological symphony of snapping shrimp, grunting fish and shifting currents. A dying reef is eerily silent.

“If a reef is alive with sound it’s most likely to stay alive right? And repopulate. And when reefs degrade they grow silent,” Barotti says.

Fish and tiny coral organisms use sound to navigate in the vast oceans to find a home, so the logic is simple: if you bring the noise back, the marine life will follow. The project utilizes “underwater boomboxes” that play recorded sounds of a healthy reef for 14 hours a day, powered by solar panels floating on the surface.

The Great Barrier Reefstudy

A study published in the journal Nature demonstrated the power of what is known as “acoustic enrichment”. Researchers at the Great Barrier Reef found that playing healthy reef sounds lured fish to degraded areas, doubling the total fish population in just six weeks. Not only did more fish arrive, but the diversity of species increased by 50%, a critical factor for long-term reef resilience.

Reefs cover just 1% of the ocean floor but support 25% of all marine life. They are the bedrock of our food supply and serve as a natural barrier, protecting coastal property from the brunt of catastrophic storms. Since 1950, the world has lost approximately half of its coral reefs due to overfishing, pollution and the climate crisis.

The root of the crisis is our planet-warming pollution. As we burn fossil fuels, we release carbon dioxide that acts like a heat-trapping blanket around the Earth. The ocean has been forced to absorb about 90% of that excess heat.

This leads to “marine heatwaves” – prolonged periods of abnormally high sea temperatures that are essentially the oceanic equivalent of a wildfire. A record marine heatwave in 2023 turned Caribbean waters into a “hot tub”, causing corals to expel the colorful algae living in their tissues. This process, known as bleaching, leaves the coral white, starving and vulnerable to disease.

Lee-Ann Rando, a second-generation scuba diving instructor, has witnessed this decline first-hand. “It’s getting quieter,” she says. “It’s really sad to say that I’ve seen the degradation a lot in the past 10 years.”

Rando captured footage of herself swimming through ghostly white, bleached reefs in 2023. “You just feel hopeless,” she says. “You feel like, ‘Am I ever gonna see this again?’”

‘Coral matchmaking’

The sound project is designed to bolster the work of the local Alligator Head Foundation. Dexter Dean Colquhoun, the foundation’s head of research, says the idea resonated with him immediately. “I’m a musician. I play piano, so I know the importance and the power of sound.”

He says the acoustic approach is a vital addition to his organization’s conservation toolkit. “It fits right into what we’re trying to do, which is to restore the reefs using as many methods as possible.”

While the speakers play the “hits” of a healthy reef, researcher Bethany Dean is working in the lab to provide the “guests” for the party. She grows coral fragments and experiments with assisted breeding, acting as a “coral matchmaker” to help the organisms reproduce in a warming world where natural reproduction is failing.

“We are looking at how you can bring these eggs and sperm together so you can actually have successful reproduction,” Dean says.

Eventually, these lab-grown coral fragments are attached to Barotti’s underwater sculptures. The result is a fusion of science and art that could begin to replace silence with the sounds of a thriving ecosystem.

“You gotta stay hopeful right?” says Rando. “I think there is hope. There are strands of it.”

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