The worrying sound of silence

Timothy Lamont's first dive into the Great Barrier Reef in Australia eight years ago was an unforgettable experience — but not a happy one. Lamont, then a PhD student at the University of Exeter, U.K., and his teammates were eager to hear the lively orchestra of fish schools in the coral ecosystem. Instead, they found a starkly quiet seascape, far from the vibrant world they'd imagined. "I remember swimming around and just feeling so empty inside, and so defeated," Lamont, now a marine biologist at Lancaster University, recalls.

Typically, the end of a dive is filled with excited chatter as people share their experiences after being unable to speak under water for hours. This time, everyone quietly unpacked their gear and drove home in silence. The only thing they carried back with them was a recording of the soundscape. Comparing it to earlier data revealed a grim reality: the reef was dying.

As the reef degraded, the once-vibrant sounds of marine life faded. "The animals responsible for the noise had died or moved away," Lamont explains. This silence discouraged juvenile fish, which rely on reef sounds to find habitats, creating a cycle of decline. The experience left them asking: can a dying reef be restored, or is its silence final?

Healthy oceans are filled with vibrant sounds. Marine animals communicate, make friends, sing, mate, and navigate using sound. This natural orchestra reveals stories about ocean health and its changes. Once, there were only two types of sounds: biophony, or sounds produced by living organisms, and geophony, the natural sounds of the Earth. Over time, marine life adapted to these two sources of sound. However, human-made sounds, or anthrophony, introduced disruptive noises, disturbing marine life that caused the extinction of many species. For ocean scientists, sound is crucial for understanding the sea. Acoustic data offer insights into soundscape quality, species distribution, and community composition, especially when visual methods are not feasible.