Advancing the Interpretation of Shallow Water Marine Soundscapes

Abstract

Soundscapes offer rich descriptions of composite acoustic environments. Characterizing marine soundscapes simply through sound levels results in incomplete descriptions, limits the understanding of unique features, and impedes meaningful comparisons. Sources that contribute to sound level metrics shift in time and space with changes in biological patterns, physical forces, and human activity. The presence of a constant or chronic source is often interwoven with episodic sounds. Further, the presence and intensity of sources can influence other sources, calling for a more integrated approach to characterizing soundscapes. Here, we illustrate this complexity using data from a national-scale effort, the Sanctuary Soundscape Monitoring Project (SanctSound), an initiative designed to support collection of biological, environmental, and human use data to compliment the interpretation of sound level measurements. Using nine examples from this diverse dataset we demonstrate the benefit of integrating source identification and site features to interpret sound levels across a diversity of shallow water marine soundscapes (<150 m). Sound levels from sites in high human use areas reflect the anthropogenic influences on the soundscape, especially when measuring broad frequency bands, whereas sites with relatively low human activity and high sound levels reveal biological features of the soundscape. At sites with large tidal changes, sound levels correlated with the magnitude of tidal flow, and sound levels during high tidal flow periods were similar to sound levels at sites near commercial shipping lanes. At sites in relatively close proximity (<30 km), sound levels diverge because of the presence of different proximate sound contributors and propagation features of the site. A review of emerging methodologies for integrated soundscape analysis, including acoustic scenes, provides a framework for interpreting soundscapes across a variety of conditions. With a global growth in monitoring efforts collecting standardized measurements over widely distributed arrays, more integrated methods are needed to advance the utility of soundscapes in marine resource management.

Sounding the Call for a Global Library of Underwater Biological Sounds

“…There is increasing evidence that the study of acoustic communities, based on acoustic characteristics of the sounds emitted by animal communities, provides ecologically relevant information (Francis et al, 2009;Farina and James, 2016;Desiderà et al, 2019;Mooney et al, 2020). Soundscapes provide unique opportunities to investigate the biodiversity and community of soniferous species, frequency and temporal niche partitioning, and organism-environment relationships (Ruppe et al, 2015;Di Iorio et al, 2021;McKenna et al, 2021). However, this field is in its infancy and requires a catalog of identified sounds to develop reliable and time-efficient classification techniques that will be necessary for describing the acoustic communities and relating them to the underlying animal assemblages (Mooney et al, 2020).…”

“…Underpinning much of this work is the ability to identify or characterize sound sources either to assess them individually or understand their contribution to the overall soundscape (Mooney et al, 2020;McKenna et al, 2021). We are beginning to understand how these biological sounds, together with anthropogenic and geophysical sounds that make up the local soundscape (Schafer, 1969(Schafer, , 1977Southworth, 1969;Krause, 2008;Hildebrand, 2009), can collectively provide information on physical habitats, biodiversity, and aquatic ecosystem health (Mooney et al, 2020).…”

State of Play in Marine Soundscape Assessments

“…For example, coastal habitats often have distinct acoustic signatures (Radford et al, 2010) that are used by a range of larval organisms to locate and select suitable settlement habitats (Simpson et al, 2005;Montgomery et al, 2006;Vermeij et al, 2010). Though methods for soundscape analyses continue to be improved to address their inherent complexities (Mckenna et al, 2021), underwater sound recording is an easily obtained metric that complements other ecosystem health measurements (Staaterman et al, 2017Peck et al, 2021. Soundscape monitoring allows for long-term detection of change in a habitat, offering potential to contribute to future ecosystem monitoring and conservation research (Mooney et al, 2020).…”

The influence of variations in background noise on Florida manatee (Trichechus manatus latirostris) detection of boat noise and vocalizations

“…Marine soundscapes vary with biological (e.g., soniferous fish, invertebrates, and mammals), physical (e.g., tides, wave, and wind), and anthropogenic (e.g., boat noise and construction) activities over time and space [ 1 – 5 ]. Consequently, background sound level and frequency spectra are dynamic.…”