04.12.19

Underwater loudspeakers could save the barrier reef

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Photo and study credit: https://creativecommons.org/licenses/by/4.0/

It’s no secret that the world is in the grips of a climate crisis, but you’d be forgiven for doing a double take if scientists told you that loudspeakers could help reverse the destruction of barrier reefs around the world.

According to researchers led by the University of Exeter, audio has proven to make a huge impact in attracting local wildlife to dying barrier reefs.

While maintaining healthy fish communities in these habitats counteracts reef degradation, the smell of the reef becomes degraded and sounds less attractive to fishes of settlement-stage in healthy states, which can lead to overall decline in the reef’s biodiversity.

To counteract this, researchers thought outside the box in a bizarre underwater real-estate advertising campaign for the local wildlife. The researchers undertook a six-week experiment to demonstrate the playback of healthy reef sound on underwater loudspeakers, leading to an increase in fish settlement and retention as well as a degradation to the local habitat.

The experiment compared fish community development on ‘acoustically enriched’ coral-rubble patch reefs with acoustically unmanipulated controls to attract local wildlife, noting a doubling in abundance of fish population overall and a surge of 50% species richness.

The researchers theorise that if this audio restoration technique is combined with active habitat restoration and effective conservation methods, fish communities could be rapidly rebuilt, potentially accelerating the rebuilding of fish communities to accelerate the recovery of the ecosystem.

Photo Credit: Lizard Island Field Guide (lifg.australianmuseum.net.au), licensed under the

In a paper published on Nature Research, the researchers said: “Reef fish populations are sustained by recruitment, whereby young fish that spend their larval stage in the open ocean use a range of sensory cues to detect, orient toward, and settle to reef habitat.

“However, degraded reefs smell and sound less attractive to juvenile fishes and receive lower levels of fish settlement than healthy systems. Artificially reversing degradation-associated sensory changes might restore habitat attractiveness, promote the settlement and retention of functionally important fish species, and enhance local-scale recovery processes. Acoustic cues are particularly amenable to artificial restoration, due to their use by a wide range of settlement-stage fishes and their ease of manipulation in field conditions using underwater loudspeakers.”

The experiment was carried out over a period of 40 days, using loudspeakers to broadcast ‘healthy’ soundscapes during a natural recruitment season Australia’s northern Great Barrier Reef, comparing the developing fish communities with those on two categories of ‘acoustically unmanipulated’ control reefs with and without dummy loudspeaker reefs.

The report stated that: “We find that acoustic enrichment enhances fish community development within an important reef fish family, across a range of specific trophic guilds and at the level of the whole community. Rebuilding fish communities in this manner shows promise as a novel tool that might complement existing techniques for the active management of degraded coral reefs.”