The Ecological Acoustic Recorder - A Powerful Tool for Monitoring Coral Reef Ecosystems

Monitoring the changing status of coral reef environments and their inhabitants is a critical management need and a considerable technological challenge, especially on reefs in remote locations. The PIFSC Coral Reef Ecosystem Division (CRED), in partnership with the Hawaii Institute of Marine Biology, is using natural ambient sounds as a way to characterize the activity of marine organisms on coral reefs and in surrounding waters. By deploying a device known as the Ecological Acoustic Recorder (EAR), scientists can learn about the presence and activity of marine mammals, fish, crustaceans and other sound-producing marine life.

Major components inside the underwater housing of an Ecological Acoustic Recorder (EAR) include the data acquisition and storage module and battery packs. Outside the housing is the hydrophone (directly above hand).

Understanding the interactions between species in coral reef biological communities requires long-term observation of relationships between species. However, while existing monitoring instruments are capable of measuring long-term physical environmental trends they currently lack the ability to observe most biological processes. Instruments that monitor biological parameters directly or through surrogates are usually unsuitable for long-term measurements in remote areas because they typically require an optical or other interface that rapidly degrades from marine biofouling. Human-mediated surveys, on the other hand, while effective at measuring biological activity, are often unfeasible for tracking long-term trends because of their inherently high logistical and staffing costs.

Noise from vessel traffic can trigger the EAR's event detection hardware, providing a record of anthropogenic activity.

Managers of marine resources, including protected resources, face particular difficulties in monitoring human-caused impacts in remote insular ecosystems where direct monitoring of human activities by field surveys is not feasible. In many such locations, the frequency and intensity of human activities, including possible illegal exploitation of resources may remain unknown unless other means of monitoring are available.

The Ecological Acoustic Recorder is a reliable, cost-effective tool for monitoring both biological processes and human activity in coral reef and other marine environments, even in remote locations. It can be left in place unattended for months at a time and is not compromised by biofouling.