Coral reefs are acoustically rich environments, with sounds generated by various marine organisms serving as critical cues for larval settlement and habitat selection. Degraded reefs often experience a decline in these natural soundscapes, leading to reduced recruitment and retention of species. Acoustic enrichment, or soundscaping, can mitigate this by broadcasting recordings of healthy reef sounds in degraded areas to attract larvae and facilitate ecosystem recovery.

Larval Recruitment Enhancement

Studies have demonstrated that acoustic enrichment can significantly increase the settlement rates of coral larvae. Gordon et al. (2019) found that broadcasting healthy reef sounds on degraded reefs in the Great Barrier Reef resulted in a twofold increase in coral larval settlement compared to control sites without sound playback. This suggests that larvae utilize acoustic cues to locate suitable habitats, and that restoring these cues can enhance recruitment success.

Fish Community Responses

Acoustic enrichment also influences fish communities. Gordon et al. (2019) reported that degraded reef patches subjected to healthy reef sound playback experienced a 50% increase in fish species richness and a doubling of total fish abundance over a 40-day period. Notably, there was also a significant rise in herbivorous fish populations, which play a vital role in controlling algal overgrowth and maintaining coral health.

Behavioral Mechanisms

The attraction of larvae to healthy reef sounds is likely mediated by innate behavioral responses. Vermeij et al. (2010) observed that coral larvae exposed to playback of reef sounds exhibited increased swimming activity and settlement rates, indicating that acoustic cues can modify larval behavior to favor settlement in acoustically enriched areas.

Ecosystem Dynamics 

By enhancing the recruitment of both corals and fish, soundscaping can accelerate the recovery of degraded reefs. The increase in herbivorous fish populations helps control algal proliferation, creating a more favorable environment for coral growth and resilience to stressors. Diverse populations of fish and other reef organisms contribute to the overall structural complexity and ecological function of the reef, and the acquisition and retention of organisms is a key metric of ecological health. 

Strategy

Soundscaping is most likely to support reefs that are otherwise healthy, or mostly healthy, but have experienced an acute loss of recruitment or retention, as opposed to persistently degraded reefs. Its effectiveness depends on the presence of viable larval sources and suitable environmental conditions for long-term survivorship, and the long-term impacts of artificial soundscapes on marine organisms are not fully understood. This approach is relatively low-cost and scalable, and has a robust mechanism with little potential for short-term negative effects if applied in favorable environments, but regional and long-term effects must be explored. 

References

• Gordon, T. A. C., et al. (2019). "Acoustic enrichment can enhance fish community development on degraded coral reef habitat." Nature Communications, 10, 5414. https://doi.org/10.1038/s41467-019-13186-2

• Vermeij, M. J. A., et al. (2010). "Coral larvae move toward reef sounds." PLOS ONE, 5(5), e10660. https://doi.org/10.1371/journal.pone.0010660