Ocean noise is damaging coral reefs, but “sound” may also hold the key to restoration

Coral reefs are among the most structurally complex and biologically diverse ecosystems in the ocean. These multifunctional natural habitats provide marine life with places to feed, shelter from predators, and reproduce, while also serving as a cornerstone of local economies and livelihoods in many coastal communities. Yet coral reefs are also among the most threatened ecosystems in the ocean. Since the 1950s, multiple pressures—including land-based pollution, overfishing, and climate change—have contributed to increasingly frequent coral bleaching events. Combined with disease and ecological imbalances, these factors have resulted in the loss of half of the world’s coral reefs.

What many people may not realize is that sound can also affect the survival of coral reefs. Recent research in marine acoustics has found that noise from shipping, seabed drilling, seismic surveys, and underwater construction can damage coral reefs, interfere with coral larvae settling, and increase stress in reef fish, potentially affecting their ability to navigate and reproduce. Persistent noise can disrupt the natural acoustic cues that larvae rely on to locate suitable habitats and may cause long-term damage to ecosystem resilience and biodiversity.

A healthy coral reef is filled with a variety of sounds that attract juvenile fish to the reef. Image source: Shaun Low /Unsplash
 

Using the Ocean’s Language as a beacon to guide marine life to suitable habitats

Yet, as the saying goes, the same force that can cause harm can also be used for good. When used strategically, sound can help rebuild fragile coral reef ecosystems. Experiments conducted by the University of Exeter, the University of Bristol, James Cook University, and the Australian Institute of Marine Science around Lizard Island on Australia’s Great Barrier Reef have demonstrated the potential of sound as a restoration tool.

After Lizard Island was hit by severe cyclones and devastating coral bleaching, its once-thriving coral reefs had become barren underwater graveyards. The research team constructed miniature reefs using coral rubble and strategically placed speakers nearby to play recordings of sounds captured from healthy coral reef ecosystems. After six weeks, the researchers found that the miniature reefs near the speakers attracted twice as many juvenile fish as reefs without sound, while species richness increased by 50%. The findings suggest that strategically using sound can help promote the rebuilding of coral reef communities.

Why can sound help marine organisms survive and reproduce? Healthy marine ecosystems naturally produce complex and diverse soundscapes—from the whistles and grunts of fish, to the scraping sounds of sea urchins feeding on the seafloor, the snapping sounds of pistol shrimp, the distinctive clicks and calls of dolphins, and the vibrations produced by lobsters with their antennae. These sounds help other organisms identify suitable habitats.

This symphony of sounds acts like a beacon, attracting young organisms searching for a place to settle, much like the bustle of a thriving city draws newcomers.

“Fish are incredibly important for maintaining healthy coral reef ecosystems. Increasing fish populations in this way can help kick-start natural recovery processes and counteract the degradation we are seeing across many coral reefs around the world,” said Tim Gordon, the study’s first author.
 

Coral Larval Settlement Rate Increased 1.7-Fold

The potential of sound has also been demonstrated by the Woods Hole Oceanographic Institution (WHOI), the largest independent oceanographic research institution in the United States. In 2023, the research team conducted a similar study in the U.S. Virgin Islands in the Caribbean. Underwater speakers were installed at three coral reefs near St. John, the smallest of the main U.S. Virgin Islands, and were used to broadcast sounds from healthy reef ecosystems. The researchers then measured the number of coral larvae that settled on ceramic tiles designed to resemble rocks within 30 meters of the speakers.

When released into the water, coral larvae drift freely with ocean currents until they find a suitable place to settle. Once they attach to a surface, they remain there and, if they survive, have the potential to develop into adult corals.

To rule out any effects caused by the physical presence of the speakers themselves, the researchers installed speakers at all three sites but played recordings of healthy coral reef sounds at only one site. They found that the average coral larval settlement rate at the site where sounds were played was 1.7 times that of sites without sound, with settlement rates reaching as high as seven times those of sites without sound in some cases.

“If you can attract some organisms to places they might not otherwise go and they survive and reproduce there, they will start producing these sounds and signals, which can attract even more organisms back,” said Nadège Aoki of WHOI. Some coral reef restoration methods require substantial amounts of labor, she noted, whereas using sound offers a more labor-efficient approach.

It is also important to address sources of threats to coral survival, such as land-based pollution and sedimentation. Image source: Rebecca Bliklen / Unsplash
 

Although research has demonstrated that sound could become a promising tool for coral restoration and enhancing biodiversity, a comprehensive approach that addresses threats at their source is still essential. Measures such as improving water quality and habitat conditions, reducing land-based pollution, and controlling sedimentation are necessary to ensure that the “residents” attracted to restored areas can truly survive and reproduce. Nevertheless, this non-invasive restoration strategy opens up new possibilities for accelerating the recovery of damaged ecosystems. By using sound as a guide, marine ecosystems may be able to restore themselves more quickly and establish a positive cycle of ecological recovery.

References

• One Earth, How the power of sound can help restore marine ecosystems

• The Guardian, Playing thriving reef sounds on underwater speakers ‘could save damaged corals’

• ScienceDirect, Noise pollution on coral reefs? — A yet underestimated threat to coral reef communities

• CNN, Underwater 'reef music' could help in coral restoration

• WBUR, New study from Woods Hole scientists suggests sound could help restore coral reefs

• Earth.Org, Can Soundscapes Save Coral Reefs?

This article is republished from the Low-Carbon Life Blog, with content jointly planned by the Delta Electronics Foundation and the Taiwan Environmental Information Association.