A comparative study of the acoustic complexity indexes between restored and degraded coral reefs in Culebra, Puerto Rico

Background/Question/Methods

Caribbean Hurricanes Maria and Irma struck Puerto Rico in 2017 causing significant damage to coral reef ecosystems. Massive losses of the reef building coral species such as Acropora cervicornis were documented. A. cerviconris is one of the major contributors to reef accretion and structural complexity. It has been demonstrated that reefs biodiversity increases as reef complexity increases. Thus, restoring of population of A. cervicocrnis is one of the preferred actions to restore the diversity of degraded reefs. In this study we compare the biodiversity of restored vs no restored reefs using the emerging technology of underwater soundscapes. Recent studies have demonstrated how degraded reefs denudes their soundscapes and affect early larvae and development stage of reef fish and invertebrates. We use two commonly acoustic indices for one-minute recordings samples of four different reef sites (two-restored and two-reference locations) in the island municipality of Culebra, P.R. Acoustic Complexity Index (ACI) was calculated using “Seewave” to acquire preliminary results on these indexes before restoration process is achieved for each site.

Results/Conclusions

Results showed significance difference for the ACI index between the study locations. If was found that restored sites had ACI values in the low frequency bandwidth, is indicative of fish presence, two time higher than degraded coral reef. Similar result was found when comparing the high frequency band which is attributed to invertebrate sounds. These results indicates that 1) restoration can indeed enhance coral reef biodiversity and 2) that acoustic monitoring is a useful tool to determine the success of coral out planting programs.