Anchored bulk carriers have substantial impacts on the underwater soundscape in Cowichan Bay, British Columbia

In recent decades shipping traffic has increased, leading to elevated underwater ambient noise levels. Research has been conducted on the noise generated by ships underway, however little is known about potential noise from ships at anchor. In coastal regions, commercial vessels can seek anchorages prior to entering port, leading to concern regarding the impacts on the soundscape and marine ecosystems. Cowichan Bay, British Columbia, a coastal region (800 Ha) 70 km away from the Port of Vancouver, was examined as a case study to understand the possible soundscape contribution from anchored bulk carriers. When a carrier anchored, sound pressure levels (SPL: 20–24,000 Hz) were elevated 2–8 dB re: 1 μPa throughout the bay. These results demonstrate the change anchored carriers can have on underwater soundscapes and is an important step in understanding the potential impact these vessels may have on marine organisms and important ecosystems. •Detailed examination of impacts of anchored commercial vessels on the soundscape•Anchored bulk carriers significantly elevate sound levels between 20 and 24,000 Hz.•Significant frequency and directional dependent additions to the local soundscape