Moonlight driven biological choruses in coral reefs

Abstract

Sounds from fish and invertebrates in coral reefs can create persistent cacophonies that can be recorded for ecosystem monitoring, including during nighttime hours where visual surveys are typically not feasible. Here, we use soundscape measurements in Hawaii and Bermuda to demonstrate that multiple coral reef communities are rapidly responsive to shifts in nighttime ambient light, with sustained changes in biological sound between moonrise and moonset. Feeding sounds from parrotfish become more prominent as moonlight increases nighttime visibility, and fish vocalizations become less prominent with moonlight, likely to minimize detection during times with increased predation. The response of invertebrate sounds to moonlight varies by location, increasing in Hawaii reefs and decreasing in Bermuda reefs. These discoveries suggest that the rising and setting of the moon triggers regular shifts in coral reef ecosystem interactions. Future acoustic monitoring of reef health may be improved by comparing soundscapes during moonlight and non-moonlight hours, which may provide early indicators of shifts in the relative abundance of separate reef communities.