Soundscapes as Sentinels: Eco-acoustics to monitor and assess ecosystem responses to anthropogenic pressures in marine protected areas

Assessing responses of species, assemblages and habitats to environmental pressures or management actions is often challenging, but essential to preserve marine ecosystems, their functions and associated services. Adjusting management practices based on impact assessment and climate scenarios is a central aspect for MPAs that requires approaches capable of capturing the dynamics of marine life and appraise responses and alterations.

Recording sounds in ecosystems allows to investigate ecological complexity from species to communities, and habitats over days and months. Furthermore, as sounds are linked to behaviours, variations in sound production reflect responses to environmental changes or human impacts. 
Based on multiple eco-acoustic studies within Western Mediterranean MPAs over several years, we show how acoustic fish communities as well as the acoustic courtship behaviour of vulnerable fish species vary with protection measures and human impact. Multivariate analyses and linear models reveal that acoustic diversity and courtship behaviour not only reflect the effectiveness of protection measures (i.e., zonation), but are also negatively related to human presence and activities, as highlighted by a highly significant decrease in sound abundance and richness with increasing boat traffic and recreational diving. Moreover, the analyses of multi-year datasets on reproductive sites reveal temporal variations of courtship calls that reflect diel biorhythms but also seasonal fluctuations that are partly altered by human activities and environmental changes. Finally, we also illustrate that analysing temporal variations allows to identify peaks in courtship calling that can be used as a proxy to identify sensitive periods during which human activities such as recreational diving and vessel traffic can be dislocated or reduced. This kind of information supports the definition of sustainable and targeted management practices, aiming at protecting functional sites and biodiversity hotspots while maintaining socio-economic activities. This work clearly highlights that long-term eco-acoustic monitoring is essential in providing an integrative and dynamic view of coastal ecosystems and organism-environment relationships in the face of environmental changes, and in supporting adaptive management.