PhD Dissertation Defense, Rebecca Van Hoeck

Dissertation title: Marine ecosystems through the lens of soundscape ecology: How biological processes, landscape structure, and anthropogenic activity affect spatiotemporal soundscape patterns

Dissertation Abstract: 

Marine soundscapes, or the collection of all sounds across a landscape, consist of dynamic patterns resulting from natural and anthropogenic sound-producing processes. Soundscape ecology is focused on understanding how these processes interact with environmental variables to create dynamic spatiotemporal patterns. As the field develops, there has been rising interest in using soundscapes as a tool to assess biodiversity and inform conservation and management decisions. However, understanding spatiotemporal soundscape patterns and their associations with ecological and environmental covariates is needed for passive acoustic monitoring to be informative.

My dissertation addresses this gap through two focal questions: (1) how do marine soundscapes vary across habitat types and is this variation explained by ecological metrics; and (2) how can soundscapes, or passive acoustic monitoring, be used to inform conservation and management priorities? To understand soundscape variation, I first compared the soundscapes of natural and artificial temperate offshore reefs, finding that their temporal patterns were similar but low frequency spectral content differed. Curious whether soundscape differences between habitat types were associated with environmental metrics, I next evaluated soundscape spatial variation across a range of estuarine habitat mosaics. I observed four distinct soundscape types that were associated with patch- and landscape-scale habitat metrics. Variation in all soundscape metrics summarized was explained by landscape-scale habitat metrics, while patch-scale habitat metrics also explained sound levels and abiotic metrics explained species-specific call rates. To evaluate how passive acoustic monitoring can be applied to conservation and management contexts, I assessed whether soundscape monitoring was a useful complement to traditional video monitoring for tracking community development following deployment of an artificial reef. Comparing the soundscape of a newly deployed artificial reef to that of a nearby established reef revealed the colonization of multiple cryptic species that were not identified from video monitoring. Lastly, I evaluated the spawning-associated grunt dynamics of an understudied spawning component of Atlantic cod in a region with imminent offshore wind energy development. Identifying the peak spawning period and aggregation site revealed that spatiotemporal interactions between Atlantic cod spawning and offshore wind energy construction are likely. Combined, this dissertation expands understanding of marine soundscape variability and demonstrates the benefit of passive acoustic monitoring for addressing applied ecological questions.