Changes in Underwater Noise and Vessel Traffic in the Approaches to Halifax Harbor, Nova Scotia, Canada

Abstract

Over the past two years, researchers at Fisheries and Oceans Canada have been running an acoustic monitoring project at multiple study sites throughout Nova Scotia, Canada to investigate baleen whale presence and levels of underwater noise. At the onset of the COVID-19 pandemic, a passive acoustic monitor (PAM) was in place in the study site located in the approaches to Halifax Harbor, a major Canadian port. This provided a unique opportunity to determine if changes in vessel noise levels occurred after pandemic restrictions were put in place. To investigate this, we analyzed and compared acoustic data collected from March 28 to April 28 and August 6 to October 22 in both 2019 and 2020. We also investigated possible changes in vessel traffic from February 1 through April 28 and July 1 through July 28 in 2019 and 2020 using terrestrial-based automatic identification system (AIS) data provided by the Canadian Coast Guard and cargo information provided by the Port of Halifax. The acoustic data were analyzed in 1/3 octave frequency bands. For the 89.1–112 Hz frequency band, we found an 8.4 dB increase in the daily minimum sound pressure level (SPL) in April 2020 compared to April 2019 due the presence of a large crane vessel stationed near the mooring site. For the period of August to October, we found an approximately 1.7 dB reduction in the same metric from 2019 to 2020. The most noticeable change in vessel composition was the dramatic decrease in the number and occurrence of pleasure craft in July 2020 compared to the same period in 2019. While this analysis looked at only a single PAM and a limited amount of data, we observed changes in sound levels in the frequency band known to be associated with shipping as well as changes in vessel traffic; we conclude that these observed changes may be related to pandemic restrictions.

Impact of the COVID-19 pandemic on levels of deep-ocean acoustic noise

“…The potential for reduction in ocean ambient noise during the COVID-19 pandemic has led to a number of recent studies based around the north American coast: the sound pressure levels close to the Port of Vancouver have been shown to have decreased by 1.5 dB during early 2020 20 ; measurements off the Oregon coast of the USA showed the sound pressure level in the 63 Hz one-third-octave band reduced in the spring of 2020 by about 1.6 dB compared to the previous five years 21 ; reductions were observed in underwater noise and vessel traffic in the approaches to Halifax Harbor, Canada 22 ; and reduction of low-frequency vessel noise was observed in Monterey Bay national marine sanctuary during the pandemic 23 . Recent studies looking at the North Sea showed a decline in sound pressure of 13% (reduction in sound pressure level of 1.2 dB) for frequencies in the range 10 Hz to 1 kHz corresponding to reduced level of shipping activity 24 .…”

Local ecological knowledge and multidisciplinary approach lead to discovery of hidden biodiversity in the deep ocean of Labrador, Canada

“…To mitigate these limitations and make the most efficient use of resources, researchers need to prioritize their exploration plans with the best available knowledge. In addition to combining multidisciplinary approaches with new technologies, integration of local knowledge can leverage lifetimes of informal surveys (Gass and Willison 2005, Breeze and Fenton 2007, Colpron 2016, Wilder et al 2016) that include areas relatively untouched by western science. Contributions from such "experts of place" are critical for addressing the current biodiversity crisis (Wilder et al 2016, Ogar https://www.ecologyandsociety.org/vol28/iss4/art4/ et al 2020) and can be instrumental to identifying ecologically and culturally important areas worthy of protection (e.g., Sheil et al 2003, Wilder et al 2016, Ogar et al 2020, Rangeley et al 2022, Parks Canada 2022.…”