The biological soundscape of temperate reefs in the Wadden sea

Monitoring coastal marine habitats presents many challenges. Often, using multiple approaches to capture different aspects of ecosystems can strengthen the information gained regarding habitat status. The use of passive acoustics to document, describe, and monitor coastal habitats through soundscapes presents one such complementary technique. Marine soundscapes have not yet been described for the Wadden Sea; an ecosystem where reef habitats have experienced major changes over time due to various human-mediated impacts. Recordings at a subtidal shellfish reef and neighbouring sandflat at six 2-week periods over a 14 month period in 2021 and 2022 provide a first catalogue of biotic acoustic signatures in this ecosystem. Furthermore, recordings from two natural reef sites were compared to recordings from two recently deployed artificial reef sites, showing similar patterns of greater biotic acoustic diversity at the natural and artificial reefs compared to nearby sandflats. These results demonstrate that fine-scale differences in habitat soundscapes exist across reef habitats within small geographic scales. This study provides the foundations for further quantitative research using PAM to monitor soundscape dynamics of the Wadden Sea and understanding the role of sound in changing coastal ecosystems.