Reef sounds attract coral and fish larvae

Underwater recordings of thriving marine ecosystems can draw drifting coral and fish larvae toward restoration zones, according to a pair of field studies led by researchers at the Scripps Institution of Oceanography. Conducted in Hawaii's Kane'ohe Bay, the research tested how sound playback combined with engineered settlement surfaces could speed the recovery of struggling reefs.

Scientists recorded sounds from a vibrant reef off Oahu, capturing crustacean snaps and fish vocalizations over a full lunar cycle. They then broadcast these noises from sunset to sunrise using an underwater speaker anchored at a sandy seafloor site near Moku o Lo'e, placing dozens of artificial habitats at varying distances from the source.

Guided by sound

Results showed that coral larvae settled in far greater numbers on surfaces closest to the broadcasting speaker. Settlement rates climbed even higher when researchers combined the sound broadcasts with protective crevice designs and a specialized bacterial surface coating known as BRINK. The findings suggest that acoustics signal favorable living conditions to drifting organisms searching for a permanent base.

A companion study used autonomous cameras to track fish activity near 3D-printed shelter structures. Young fish appeared between four and fourteen times more often around the active speakers compared to silent control areas, demonstrating that acoustics strongly influence young fish recruitment alongside coral colonization.

Researchers noted that establishing healthy fish communities is vital for growing reefs because many species graze on algae that can otherwise smother young corals. The tested acoustic and structural tools are slated for deployment in a major hybrid reef barrier project scheduled for installation off Oahu.