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Damaged coral reefs could be restored using underwater loudspeakers

Protected waters still hurt by climate change
How ocean habitats are feeling the impact of global warming 05:52

Coral reefs around the world have long suffered from the effects of climate change and overfishing. But scientists haven't given up on saving the natural wonders — and now, a new study shows loudspeakers could help. 

Researchers set up underwater loudspeakers in Australia's northern Great Barrier Reef in late 2017, blasting recorded sounds of healthy reefs to encourage young fish to return to, and settle in, damaged ones. In a study published Friday in the journal Nature, the researchers said this "acoustic enrichment" can help revive coral reefs globally. 

"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 and professor Steve Simpson of the University of Exeter said in a press release Friday

"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 said.  

Researchers found that twice as many fish flocked to the "acoustically enriched reefs" compared to areas where no sound was played — a crucial factor in kick-starting natural recovery processes. And not only did the six-week loudspeaker experiment double the total number of fish arriving at the habitats. It also increased the number of species in the region by 50%.

The experiment brought in fish from every level of the food chain — herbivores, detritivores, planktivores and predatory piscivores. 

Scientists warn that bringing fish back to damaged reefs isn't the only change necessary to restore them. But fish are responsible for a number of maintenance duties, including cleaning reefs and creating space for coral regrowth — important aspects of recovery. 

"If combined with habitat restoration and other conservation measures, rebuilding fish communities in this manner might accelerate ecosystem recovery," said professor Andy Radford, a co-author from the University of Bristol. "However, we still need to tackle a host of other threats including climate change, overfishing and water pollution in order to protect these fragile ecosystems."  

According to a study published earlier this year, baby coral in the Great Barrier Reef have declined by 89% due to mass bleaching in 2016 and 2017. Deadly back-to-back bleaching events have devastated the area, and in August, the government agency that manages the reef downgraded its outlook for the corals' condition from "poor" to "very poor" due to warming oceans.

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