Hawaiian researchers boost coral settlement using reef sounds and bacteria-coated structures

Researchers conducted a reef-restoration trial in Kāneʻohe Bay, positioning 37 engineered structures at about 4.5 metres depth and broadcasting recordings of a thriving reef from sunset to sunrise for two weeks. The audio, rich in fish and snapping-shrimp sounds, was intended to mimic the louder environment of healthy reefs, which may guide drifting larvae. Some structures were covered with BRINK, a bioactive coating containing live bacteria that provide chemical settlement cues.

After spawning events in 2023 and 2024, divers found the highest coral larval settlement on the units nearest the speaker, with the bacteria-coated pieces performing best. Autonomous cameras also recorded a substantial rise in fish larvae presence, ranging from four to fourteen times more than at silent sites. While the results are promising, the researchers note that settlement does not guarantee long-term reef development and that further trials are needed across locations and seasons.