Photo: Hiroko Yoshii // Unsplash

The Inertia

New research indicates that coral may respond to the sounds of a healthy reef. Researchers at the Woods Hole Oceanographic Institution (WHOI) found that coral larvae were attracted to sites where they broadcast audio of a thriving reef, according to a study published in the journal Royal Society Open Science.

“A healthy coral reef will typically feature many low-frequency sounds of croaks, purrs, and grunts produced by fishes against a near-constant background of crackles and pops produced by snapping shrimp,” Nadège Aoki, a doctoral candidate at WHOI and lead author on the research paper, explained to AFP. A degraded reef, on the other hand, is “much quieter.”

To find out how coral reacted to these healthy reef sounds, scientists created a device called the reef acoustic playback system (RAPS). The system consisted of an underwater speaker fixed with cable ties to a cinderblock anchor on the seafloor, which was connected to a waterproof electronics housing mounted atop a surface buoy. The RAPS was powered by solar-charged batteries on the surface. This device could then continuously play recordings of ‘healthy’ reefs underwater.

For the experiment itself, the researchers distributed mustard hill coral larvae at three reefs in the US Virgin Islands – one healthy and two degraded. One of the degraded reefs was bathed in healthy reef sounds from a RAPS system, while the other had a silent RAPS system, as a control.

They found that the coral larvae vastly preferred the sites with healthy reef sounds. “Porites astreoides settled at significantly higher rates at the acoustically enriched sites, averaging 1.7 times (up to maximum of seven times) more settlement compared with control reef sites without acoustic enrichment,” explains the paper.

“Now we have also demonstrated that the local sound environment is very important for these corals, and that playing reef sounds can potentially be a vital tool in the effort to restore coral reefs,” added Aoki.


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