Multi-site validation of shipping noise maps using field measurements.

Underwater radiated noise from shipping is globally pervasive and can cause deleterious effects on marine life, ranging from behavioural responses to physiological effects. Acoustic modelling makes it possible to map this noise over large areas and long timescales, and to test mitigation scenarios such as ship speed reduction or spatial restrictions. However, such maps must be validated against measurements to ensure confidence in their predictions. This study carried out a multi-site validation of the monthly and annual shipping noise maps for 2019 produced as part of the Joint Monitoring of Ambient Noise in the North Sea (JOMOPANS) programme. Spectral, spatial, and temporal differences between predictions and measurements were analysed, with differences linked to uncertainty in model input data and additional sources of anthropogenic noise in the measurements. Validating shipping noise models in this way ensures they can be applied with confidence in future management decisions to address shipping noise pollution.

Exploring how vessel activity influences the soundscape at a navigation lock on the Mississippi River.

Vessel sound is now globally recognized as a significant and pervasive pollutant to aquatic life. However, compared to marine environments, there is a paucity of data on sound emitted by vessel activity in freshwater habitats. The Upper Mississippi River (UMR) is home to a diverse array of aquatic life as well as being a key route for barge transportation with 29 locks and dams. In this study, passive acoustic monitoring was conducted at Lock and Dam 19 near Keokuk, Iowa, on the UMR between 20 June - August 28, 2019 to coincide with peak navigation use. There was a significant increase in median sound pressure level (SPL; 50-12,000 Hz) recorded during vessel passages (123 dB re. 1µPa for recreational vessels and 137 dB re. 1µPa for commercial vessels) compared to median background levels (111 dB re. 1µPa). Results provide information on the ambient soundscape at a navigation lock, providing a baseline essential for future studies gauging the effect of anthropogenic sound on aquatic life. Lock 19 has also been identified as a potential site for acoustic deterrent deployment to prevent invasive fish movements. The results of this study can help determine the sound level or frequency deterrents would need to emit, to avoid those currently produced during vessel passage.

Exploring spatial and temporal trends in the soundscape of an ecologically significant embayment.

The Hauraki Gulf, a shallow embayment in north-eastern New Zealand, provides an interesting environment for ecological soundscape research. It is situated on a tectonic plate boundary, contains one of the busiest ports in the southern hemisphere and is home to a diverse range of soniferous animals. The underwater soundscape was monitored for spatial and temporal trends at six different listening stations using passive acoustic recorders. The RMS sound pressure level of ambient sound (50-24,000 Hz) at the six listening stations was similar, ranging from 90-110 dB re 1 µPa throughout the recording period. Biophony had distinct temporal patterns and biological choruses of urchins were significantly correlated to temperature. Geophony and biophony followed the acoustic niche hypothesis, where each sound exhibited both temporal and frequency partitioning. Vessel passage sound were identified in 1.9-35.2% of recordings from the different listening stations. Vessel sound recorded in the Hauraki Gulf has the potential to mask concurrent geophony and biophony, sounds that may be important to marine life. This study provides a baseline of ambient sound, useful for future management strategies in shallow embayments where anthropogenic pressure is likewise increasing.