Dying coral reefs can be revived by playing sounds of healthy reefs on underwater loudspeakers to attract fish

Healthy coral reefs are remarkably noisy places and young fish home in on these sounds when they are looking for a place to settle. The study found recordings of such sounds doubled the total number of fish arriving at the patches of reef habitat


                            Dying coral reefs can be revived by playing sounds of healthy reefs on underwater loudspeakers to attract fish

Scientists have discovered an offbeat approach to restoring the dying coral population around the world. The key to their revival are sounds of healthy reefs, say experts.

Playing sounds of healthy reefs can bring back the reefs' lost inhabitants: fish. They have a crucial role to play in rebuilding extremely degraded coral communities.

"Fish are critical for coral regrowth, they keep seaweed in check, giving corals space to grow," Dr. Steve Simpson, Professor at the University of Exeter, tells MEA WorldWide (MEAWW). 

These findings build on the study conducted about 18 years ago. Dr. Simpson discovered that fish were attracted to reefs with noise. Healthy coral reefs are extremely noisy places, with the crackle of snapping shrimp and the whoops and grunts of fish.

It is this noise that attracts young fish when they are looking for a place to settle. Over the years, researchers also showed that sounds of degraded reefs are less attractive to fish since fewer fish gathered at the degraded site.

Coral degradation has become a common sight, thanks to an increase in greenhouse emissions. What is more, humans increasingly depend on them: the reefs prevent $94 million in flood damages every year.

The US ranks in the top 10 countries to receive risk reduction benefits from coral reefs, according to the National Oceanic and Atmospheric Administration.

Human activities are damaging these reefs. For instance, they became degraded due to warming seas, Dr. Andy Radford, a co-author from the University of Bristol, tells MEAWW.

Because of this, only dead corals and far fewer inhabitants remain in these ecosystems. As inhabitants disappear, degraded corals become ghostly quiet, he adds.

As warming seas degrade coral reefs, only dead corals and far fewer inhabitants remain in these ecosystems. As these inhabitants disappear,  degraded corals become ghostly quiet. (Tim Gordon, University of Exeter)

To demonstrate whether these sounds can attract fish and thereby rebuild the reef-fish community, scientists placed underwater loudspeakers playing healthy reef recordings in patches of dead coral in Australia's recently devastated Great Barrier Reef.

The study found that recordings of healthy reef sounds doubled the total number of fish arriving at the patches of reef habitat. Further, the researchers saw a 50% increase in the number of different groups of fish gathering at the site. 

The damage that has been inflicted on many coral reefs around the world can be counteracted by this new technique, explains lead author Tim Gordon, of the University of Exeter.

Despite this, the road to recovery is long. "Even the fastest-growing corals need 10-15 years for full recovery (assuming there are no major adverse effects in that time), and others taking much longer."

"Because the frequency of events such as bleaching and cyclones has increased, the undisturbed period for coral regrowth is becoming less and less likely," Dr. Radford tells MEAWW.

He also adds that though their findings could speed up ecosystem recovery, it is not enough as a standalone method.

"It is a promising technique for management on a local basis but needs to be combined with habitat restoration and other conservation measures. We hope to have added to the toolbox of techniques available in the fight to save these precious and vulnerable ecosystems," he shares.

Nevertheless, the team is keen on expanding their study. "Our next challenge is to work out ways of broadcasting healthy reef sounds over whole reefs to promote recovery," Dr. Simpson adds. The study was published in Nature Communications.

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