Coral reef & temperate coastal soundscape features evident in directional and omnidirectional passive acoustic time series

Abstract

Biologically complex coastal environments, such as coral reefs, demonstrate an equally rich ambient soundscape. Bioacoustic features of coastal soundscapes are closely tied with relative ecosystem health, functional groups present, and can be linked with specific behaviors. Biological contributions to ambient soundscapes have distinctive qualities as compared to sound associated with physical processes (i.e. wind and wave noise). While some biological components are readily identifiable, such as marine mammal or fish calls, the background noise associated with hundreds of thousands of biological clicks, snaps, and pops is not as well studied but contains a wealth of information about the ecosystem. A 64-element line array with 4.5 kHz design frequency was deployed for several field experiments off the coast of Kona, Hawaii in 2019 and 2020. Soundscape data from Hawaii were compared with comparable omnidirectional time series from Bermuda (2020) and coastal New England rocky reefs (2020–2021). Similarities in certain spectral features associated with biological sound sources were found between these unique ecosystems. The characteristic coral reef evening chorus, or significant increase in sound levels immediately prior to sunset, was consistent in Hawaii and Bermuda with comparable crepuscular changes in coastal New England.