Reefwatch: Using soundscape to monitor reef health

While physical parameters (e.g. currents, temperature, water quality, visibility, salinity, etc) of the environment around coral reefs are relatively easy to measure with instruments, biological parameters (e.g. percentage of coral cover, species or genus composition of coral and fish, larvae settlement, extent of bleaching, etc.) are often measured manually via visual and diver surveys. Such surveys are manpower intensive and expensive, and especially difficult in the turbid waters around Singapore. Ambient underwater sound is a well-known cue for orientation of settlement stages of coral reef organisms. The sounds made by snapping shrimp that inhabit reefs may be critical in coral reef recruitment. A distillation of the major findings demonstrate the importance of acoustic frequencies in the 2.5-20 kHz range on reef fish settlement. It is therefore reasonable that acoustic signals originating from invertebrate feeding and/or snapping shrimp can potentially be analyzed to yield critical information on coral reef ecosystem health, in general. We are developing techniques to analyze acoustic recordings made at reefs to infer aspects of the reef health.

A variety of biological sounds from a reef would suggest a reef teeming with life and health. It is perhaps even likely that larvae evolved to follow reef sound cues to choose healthy reefs for settlement. So it is reasonable to expect that the sound of reefs would tell us much about the health of the reef’s ecosystem. Although we do not expect the acoustic monitoring to be a replacement for visual surveys, they can be expected to supplement visual surveys and improve our ability to monitor reef health at little additional cost.