Wind-dependent and traffic-generated noise in marine mammal habitat: Assessment across three frequency bands in the St. Lawrence estuary

Underwater sound is crucial for cetaceans, aiding behaviors such as foraging, communication, navigation, and reproduction. The St. Lawrence Estuary (eastern Canada), a key habitat for several cetacean species, also serves as a major shipping corridor connecting the Great Lakes to the Atlantic Ocean, which exposes marine mammals to elevated levels of anthropogenic noise. Given the threatened status of species such as the blue whale (Balaenoptera musculus) and the beluga whale (Delphinapterus leucas), quantifying underwater noise and identifying its sources is essential for effective conservation. This study, conducted within the framework of the MARS (Marine Acoustic Research Station) project, analyzes acoustic data recorded from August to October 2021 in the Laurentian Channel. A model was developed to classify and quantify wind- and shipping traffic-generated noise across three biologically relevant frequency bands: 50, 300, and 6300 Hz. Results show that at 50 Hz, used by blue whales, traffic noise dominates nearly 100% of the time. At 6300 Hz, used by belugas, traffic noise accounts for 24.4% of the measured levels. These findings emphasize the importance of frequency- and species-specific assessments to inform mitigation strategies and support the development of sustainable marine traffic policies.