Using soundscapes to monitor species assemblages and vessel presence in two Australian marine parks

Soundscape ecology is a relatively new field with great potential for diversifying the manner in which we monitor long-term health and anthropogenic impacts both on land and in the ocean. This field characterizes acoustic interactions within an environment, integrating biological, geological, and anthropogenic sound sources. In this study we assessed the overlap of sound sources in time and frequency to establish a baseline measure of the soundscapes within two Marine Protected Areas (MPAs) along the east coast of Australia: Cod Grounds Marine Park (CGMP) and Solitary Islands Marine Park (SIMP). Acoustic recordings were originally used to inform activity patterns of vessels for management purposes, and this study presents a noninvasive, high resolution method of simultaneously assessing the presence of multiple species as well as human activity. Within each MPA, acoustic recorders were deployed twice: on 01 July 2018 and 10 August 2018 in CGMP and SIMP, respectively (32 – 35 days, continuous recordings) and on 12 December 2018 in both MPAs (34 – 70 days, 30-minute duty-cycled recordings). These acoustic recordings allowed us to determine hourly presence of sounds between 20 Hz and 24 kHz in frequency. Biological sources at both sites included dolphins, continuous snapping shrimp, diel patterns of fish choruses, and seasonal presence of baleen whale species. Anthropogenic sources were largely dominated by vessel transit, which was further classified into distant vessels and closer approaches likely within the MPA. Along with additional deployments at these sites, other efforts are forthcoming in several remote MPAs aimed at understanding the soundscapes throughout a wider number of MPAs. Longer-term monitoring efforts will allow alterations in soundscapes to be tracked relative to climatic and anthropogenic changes.