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Loudspeaker Helps Corals

Coral reefs are having a tough time, due to warming oceans. Conservationists are worried about how to save them, but a creative new solution might come as music to their ears.

Scientists had the idea to play underwater sounds on degraded portions of Australia's Great Barrier Reef to replicate the noises heard on a healthy, active reef. Dr. Simpson, one of the study authors, said: "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." 

These are sounds that young fish are attracted to once they have hatched and spent their larval stage in the open ocean. The problem is that once a reef degrades, the reef smells and sounds less attractive to the juvenile fish. Those fish will then opt to settle elsewhere, causing the reef to degrade further.

Hence the 'sound experiment' in which the reefs were given one of three experimental treatments. They either had no loudspeaker, a dummy loudspeaker (to control for visual cues that might affect fish behaviors), or a real loudspeaker (a.k.a. “acoustic enrichment treatment”) that played reef sounds. Playback occurred for 40 consecutive days, always at nighttime, which is when fish settlement typically occurs. 

At the end of the experiment, the researchers found that acoustically-enriched reefs had attracted fish at a faster rate than non-enriched reefs, with twice as many juvenile damselfishes on acoustically enriched reefs when compared to the two control group reefs. Biodiversity also increased by 50 percent, with more than just damselfishes attracted to the sound.

Although the presence of fish alone cannot restore a coral reef to good health, study author Dr. Meekan explained that “recovery is underpinned by fish that clean the reef and create space for corals to regrow.” The study shows that acoustic enrichment could “facilitate a ‘snowball effect’, whereby other fish respond positively to communities established earlier, causing further increases in the settlement.”

Source: Treehugger

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