Underwater speakers that pump out the buzz of bustling coral life could be used to help reefs recover from the damaging effects of climate change and other environmental woes. 

Reporting in the journal Nature Communications, scientists from the UK and Australia have been toying around with using “acoustic enrichment” to attract life back to damaged coral reefs in Australia's Great Barrier Reef, the world's largest coral reef system. 

Corals are deeply intertwined with their wider ecosystem. Not only do they provide a home for fish and a number of invertebrates, but their guests also provide them with nutrients. However, if a reef becomes unhealthy, they can also lose their lodgers, turning the reefs into a ghost town, sparking a downward spiral of decline. This new piece of research has used the “acoustic enrichment” to mimic the natural noises of bustling and healthy coral reef in the hopes of attracting back visitors. 

“Healthy coral reefs are remarkably noisy places – the crackle of snapping shrimp and the whoops and grunts of fish combine to form a dazzling biological soundscape. Juvenile fish home in on these sounds when they’re looking for a place to settle,” senior author Professor Steve Simpson, a marine biologist from the University of Exeter, said in a statement.

“Reefs become ghostly quiet when they are degraded, as the shrimps and fish disappear, but by using loudspeakers to restore this lost soundscape, we can attract young fish back again," he added.

Researchers from the University of Exeter and the University of Bristol in the UK, along with Australia’s James Cook University and Australian Institute of Marine Science, tested out this theory on over 30 patches of dead coral rubble in Australia’s northern Great Barrier Reef using underwater loudspeakers that played the recordings of a healthy reef. 

After 40 days of the treatment, they found that the coral patches had a 50 percent increase in species richness. Crucially, the diversity of species involved an array of fish from all sections of the food web, including herbivores, scavengers, plankton-eaters, and predatory carnivores. 

_{Turn the sound on for sounds of a healthy, and not so healthy, reef.} 

This is just the start of the reefs’ recovery. Once the fish have returned, the real hard work begins for the corals, which must recover their own symbiotic algae and continue to battle against an increasingly hostile environment.

Nevertheless, the research has demonstrated that this technique could be an invaluable weapon in resisting the mounting challenges faced by the world’s coral reefs. 

“Whilst attracting more fish won’t save coral reefs on its own, new techniques like this give us more tools in the fight to save these precious and vulnerable ecosystems,” explained lead author Tim Gordon.

“From local management innovations to international political action, we need meaningful progress at all levels to paint a better future for reefs worldwide.”