Ocean calls: Dead coral reefs are beings saved one musical number at a time

A healthy coral reef is very noisy, with swimming fishes, crackling shrimps and this attracts other fish.

Saving the corals reefs have become the need of the hour and many marine biologists are engaged in finding ways to help in their regeneration. The dozens of researchers engaged in these studies are finding new and creative ways to help these colourful environments to survive.

In a new experiment, researchers from Australian and British universities placed speakers underwater and played the sounds of healthy corals in an attempt to attract fish to patches of dead coral reefs. This method might sound extremely weird but it worked. Fish have been flocking to these coral patches and staying, which they hope will jump-start the recovery process for the corals.

Ocean calls: Dead coral reefs are beings saved one musical number at a time

Healthy coral reef patches are noisy and they attract other fish to come reside in it.

"Fish are crucial for coral reefs to function as healthy ecosystems," said lead author Tim Gordon, of the University of Exeter in a statement. "Boosting fish populations in this way could help to kick-start natural recovery processes, counteracting the damage we're seeing on many coral reefs around the world."

Australian Institute of Marine Science fish biologist Dr Mark Meekan added, "Of course, attracting fish to a dead reef won't bring it back to life automatically, but recovery is underpinned by fish that clean the reef and create space for corals to regrow."

Researchers from UK's University of Exeter and University of Bristol, and Australia's James Cook University and Australian Institute of Marine Science created 30 patches of dead corals around The Great Barrier Reef. From these 30 patches, they placed the speakers around 11 patches and played the sounds of the healthy reefs from sunset and continued till sunrise because these are the timings that fish swim up to the reeds to explore and settle. On the other 22 patches, no sounds were played, although, in half of these, a dummy speaker was present.

A healthy coral reef, it turns out, is very noisy and this attracts the fish. These reefs are home to tons of other living creatures, other than coral polyps and the algae that reside in them. Fish, corals, lobsters, clams, seahorses, sponges, and sea turtles are only a few of the thousands of creatures that rely on the reefs for their survival.

Corals live a symbiotic life with a type of algae that help them feed, discard waste and gives the reef their colour.

Corals live a symbiotic life with a type of algae that help them feed, discard waste and gives the reef their colour.

Corals are invertebrate animals belonging to a large group of animals called Cnidaria. Each individual coral animal is called a polyp, and they live in groups of hundreds to thousands of genetically identical polyps that form a 'colony'. Coral polyps have developed this relationship with tiny single-celled plants, known as zooxanthellae.  Inside the tissues of each coral polyp, live these microscopic, single-celled algae, sharing space, gas exchange and nutrients to survive. This symbiosis between plant and animal also contributes to the brilliant colours of coral that can be seen while diving on a reef.

A dead reef makes no sound as all the animals abandon it. "Healthy coral reefs are remarkably noisy places - the crackle of snapping shrimp and the whoops and grunts of fishes combine to form a dazzling biological soundscape. Juvenile fish are attracted to these sounds when they're looking for a place to settle," said senior author Professor Steve Simpson 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

The study found that broadcasting healthy reef sounds doubled the total number of fish arriving onto experimental patches of reef habitat as compared to other dead patches. They also found that it increases the number of species present by 50 percent.

However, this method can only work in tandem with other restoration and coral conservation methods. The main problem that needs to be tackled is climate change.

A bleached patch of coral does not support the alage and is hence considered dead.

A bleached patch of coral does not support the algae and is hence considered dead.

Australia’s Great Barrier Reef is threatened by climate change and water pollution. Coral bleaching due to warming waters are killing off these colourful creatures and it has been an annual occurrence. The only way to stop it is to decrease water temperatures. However, a new study has shown that some corals are also adapting to warming waters and continue to thrive. But that does not mean we should stop our efforts.

Professor Andy Radford, a co-author from the University of Bristol, said, "Acoustic enrichment is a promising technique for management on a local basis. If combined with habitat restoration and other conservation measures, rebuilding fish communities in this manner might accelerate ecosystem recovery. 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."

new method practised in Jamaica has found that corals can be revived, by first growing them on strings and then transplanting them to larger reefs.

The findings from this study have been published in the journal Nature Communications.

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