Advancing underwater soundscape in lagoon environments

Coastal environments are increasingly exposed to multiple human pressures, among which underwater noise represents a growing but still unevenly quantified component. Shallow transitional systems such as lagoons are particularly challenging to investigate acoustically, due to spatially heterogeneous shallow bathymetry, soft muddy substrates, strong tidal forcing, and intense maritime activity linked to navigation, port infrastructure, and tourism.

High-quality underwater acoustic observations are commonly based on hydrophones and dedicated recording platforms, whose costs and operational constraints often restrict spatial coverage and monitoring duration. The recent availability of low-cost underwater acoustic recorders offers new perspectives for dense and flexible observational networks, but their lack of calibration and sensor-to-sensor variability limit their applicability for quantitative soundscape analyses.

We propose an observational and calibration framework designed to enable the quantitative use of low-cost acoustic sensors in shallow lagoon settings. A spatially distributed array of recorders was deployed across multiple sites in the Venice Lagoon, covering complete diel cycles. Sensor responses were characterised and cross-validated through controlled measurements against a reference-calibrated hydrophone, allowing conversion of recorded signals into physical units and improving inter-sensor consistency. Acoustic observations were analysed jointly with ancillary environmental and anthropogenic data, including tidal conditions, vessel presence, and meteorological parameters.

Beyond the methodological developments, the calibrated recordings are used to perform a preliminary examination of the lagoon soundscape, with the aim of identifying dominant temporal structures and investigating the relative roles of natural processes and human activities. Enhancing data reliability and inter-sensor comparability, this approach has the potential to support more robust soundscape analyses in shallow lagoon systems and to inform future geophysical, ecological, and management-focused studies.