Lack of consistent diurnal trends in acoustic metrics from restored Coral Reefs

Abstract

Once vibrant ecosystems, coral reefs are degrading at unprecedented rates due to natural and human—induced disturbances, necessitating immediate restoration and conservation efforts. Evaluating the success of these projects often involves assessing changes in reef biodiversity. Bioacoustics has emerged as a promising, non—invasive method for such evaluations, though its efficacy remains debated. This study aimed to determine whether the diurnal soundscapes of restored coral reefs are consistent across different time frames (months) and spatial scales (reefs), which is crucial for developing reliable monitoring tools for reef health. To achieve this, 2 commonly used acoustic indices, the Acoustic Complexity Index (ACI) and Mean Sound Pressure Level (SPL), were employed to describe the underwater soundscape of 3 restored coral reefs in Culebra, Puerto Rico. The results showed that neither acoustic index followed a clear diurnal pattern, with considerable variation across studied locations and sampling days. The lack of consistent diurnal patterns across space and time suggests that ACI and SPL alone may not be ideal for comparing coral reef health, particularly as indicators of biodiversity. Instead, these sound metrics should complement other monitoring methods, such as visual and video census techniques, when evaluating the biodiversity of coral reef ecosystems.