A noisier coral reef is going to be a healthier reef, a new study finds.
Researchers from Exeter University and the University of Bristol’s School of Biological Sciences, both in England, found a clear association between overall noise level generated by a reef’s denizens and the amount of living coral present: Healthy reefs mean more coral structures, more fish and other creatures calling that coral home; and more inhabitants mean more noise.
This finding could change the way scientists monitor reefs, and give insight into behavior seen in juvenile fish, the researchers said.
Reefs can be surprisingly noisy places, with fish and invertebrates producing a cacophony of clicks and grunts. Each coral reef is subtly different depending on its size and the species that live there. By analyzing recordings of reefs in the Pacific Ocean taken with hydrophones, marine biologists have found clear differences from reef to reef.
“This study provides evidence that reef-generated sound contains a real richness of information,” said study researcher Steve Simpson of Exeter University.
“This would provide fish and invertebrates with the cues they need to assess the quality of potential settlement sites before they can see them, a bit like wandering around a music festival eavesdropping on different bands before choosing where to pitch your tent. It may even provide the information that enables some fish to return to the very reef on which they were originally spawned.”
Reefs are underwater structures made from calcium carbonate secreted by corals, which are colonies of tiny living animals. Reefs are also home to 25 percent of all marine species, including fish, molluscs, echinoderms and sponges.
Young fish and coral return to reefs after spending their first few weeks of life in the water column. The researchers suspect the coral animals search for homes by listening for, and moving toward reef noise, which can travel several kilometers out to sea.
The study, conducted in the Las Perlas Archipelago off the Pacific coast of Panama, also highlights the potential for using audio recordings to monitor reef health, which is threatened by ocean warming, acidification and overfishing.
Scientific studies of reefs involve scuba divers, huge quantities of equipment and can be expensive. With this new method, two minutes of sound recording with a hydrophone (underwater recording device) is all researchers need.
“Investigation of the acoustic properties of reefs is a relatively new area of science but already we’re realizing that there’s more to underwater noises than just whale and dolphin communication,” said study researcher Emma Kennedy, a Ph.D. candidate at Exeter. “Reefs may be broadcasting a lot of information out into the sea that both humans and marine animals could use.”
The team is hoping their findings, published online in the Journal of Experimental Marine Biology and Ecology, will prompt other scientists to investigate reef sound further.