Coral Lullabies

For some coral, home isn’t where the heart is—it’s where the sounds are. A recent study showed that one type of coral prefers to settle on reefs that sound healthy—even if they’re not.

Young corals, known as larvae, float or swim through the water for a while. When they find a good spot, they drop to the bottom and grab hold. They use several cues to find the best locations, including the lighting and chemistry. And according to the study, one of those cues might be sounds.

Biologists recorded the sounds of both healthy and un-healthy reefs in the U.S. Virgin Islands. Healthy reefs are noisy. They feature the clicks of snapping shrimp and the grunts and groans of fish. Unhealthy reefs are much quieter.

The scientists placed small groups of larvae in special containers on three reefs. One reef was healthy, with a good amount of coral. The others had less coral and much more algae, which can kill a reef.

Researchers played the sounds of a healthy reef to the larvae on one of the damaged reefs. On the other two reefs, the larvae had only the natural sound of the environment.

On average, the larvae that were played the healthy sounds were 1.7 times more likely to settle on the reef than those at the other reefs—even the healthy one. So playing a nice lullaby into damaged reefs might lure new generations of coral in the years ahead.

Our thanks to T. Aran Mooney of the Woods Hole Oceanographic Institution for the reef sounds.