Large Vessel Activity and Low-Frequency Underwater Sound Benchmarks in United States Waters

Abstract

Chronic low-frequency noise from commercial shipping is a worldwide threat to marine animals that rely on sound for essential life functions. Although the U.S. National Oceanic and Atmospheric Administration recognizes the potential negative impacts of shipping noise in marine environments, there are currently no standard metrics to monitor and quantify shipping noise in U.S. marine waters. However, one-third octave band acoustic measurements centered at 63 and 125 Hz are used as international (European Union Marine Strategy Framework Directive) indicators for underwater ambient noise levels driven by shipping activity. We apply these metrics to passive acoustic monitoring data collected over 20 months in 2016–2017 at five dispersed sites throughout the U.S. Exclusive Economic Zone: Alaskan Arctic, Hawaii, Gulf of Mexico, Northeast Canyons and Seamounts Marine National Monument (Northwest Atlantic), and Cordell Bank National Marine Sanctuary (Northeast Pacific). To verify the relationship between shipping activity and underwater sound levels, vessel movement data from the Automatic Identification System (AIS) were paired to each passive acoustic monitoring site. Daily average sound levels were consistently near to or higher than 100 dB re 1 μPa in both the 63 and 125 Hz one-third octave bands at sites with high levels of shipping traffic (Gulf of Mexico, Northeast Canyons and Seamounts, and Cordell Bank). Where cargo vessels were less common (the Arctic and Hawaii), daily average sound levels were comparatively lower. Specifically, sound levels were ∼20 dB lower year-round in Hawaii and ∼10-20 dB lower in the Alaskan Arctic, depending on the season. Although these band-level measurements can only generally facilitate differentiation of sound sources, these results demonstrate that international acoustic indicators of commercial shipping can be applied to data collected in U.S. waters as a unified metric to approximate the influence of shipping as a driver of ambient noise levels, provide critical information to managers and policy makers about the status of marine environments, and to identify places and times for more detailed investigation regarding environmental impacts.

Widespread passive acoustic monitoring reveals spatio-temporal patterns of blue and fin whale song vocalizations in the Northeast Pacific Ocean

“…Missed detections may occur when the selected background frequencies and/or the signal frequencies are overwhelmed by sounds from other sources. The influence of anthropogenic sound sources such as vessel noise is prevalent at the Olympic Coast, Cordell Bank, and Channel Islands recording locations, with large container ships being particularly dominant and producing sound at frequencies that overlap with blue and fin whale calls (McKenna et al, 2013;Haver et al, 2018;Haver et al, 2020;Haver et al, 2021). Therefore, the potential for masking could be high in these locations resulting in an underestimate of call presence and reduced communication space for these species (Clark et al, 2009;Hatch et al, 2012;Cholewiak et al, 2018).…”

“…Therefore, the site-specific and seasonal levels in background noise need to be heavily considered when applying this technique to different sites and interpreting those results. Cross-referencing blue and fin whale vocalizations, and vessel noise frequency bands with vessel tracking data could assist in a broader understanding of the low-frequency soundscape drivers at the NRS sites (Haver et al, 2020;Haver et al, 2021).…”

“…This network provides multi-year, continuous recordings of low-frequency underwater sound between 10 Hz and 2 kHz (Haver et al, 2018). Data from this acoustic network have been analyzed to assess longterm patterns of the ocean soundscape across sites and to understand how bioacoustic activity, anthropogenic noise, and physical processes contribute to the ambient sound levels (Haver et al, 2018;Haver et al, 2019;Haver et al, 2020;Haver et al, 2021).…”

Understanding vessel noise across a network of marine protected areas

“…Ten listening stations with data in April of 2019 and 2020 were used to understand changes in vessel noise presence metrics related to early-COVID shutdowns. Previous studies have used both 63-Hz and 125-Hz one-third octave bands as representative of noise from marine vessel tra c (Haver et al, 2021). This study summarized sound pressure levels in the 125 Hz one-third octave band, which is representative of a wide range of vessel sizes.…”

“…Although AIS was not designed with research or conservation planning in mind (Robards et al, 2016), many studies have demonstrated the multifaceted bene ts of this monitoring data (Welch et al, 2022). Listening for underwater vessel noise using passive acoustic monitoring provides information on vessel presence (Haver et al, 2023;Kline et al, 2020), speci c noise output (ZoBell et al, 2021(ZoBell et al, , 2023, and cumulative noise added to the marine environment (Haver et al, 2021). The spatial scale of hearing vessel noise depends on sound propagation conditions in the local environment, while the temporal scale varies by instrumentation limitations and project goals.…”