As the Skimmer is covering the various ways that the COVID-19 pandemic has impacted marine ecosystems and communities, a likely reduction in ocean noise is one possible bright spot, says an article Published in OpenChannels.
About the study
Almost all reports collected related to ocean noise and marine mammals were off the West Coasts of the U.S. and Canada in the first half of 2020.
To help broaden our understanding, we asked scientists from Applied Ocean Sciences, a collective of ocean consultants with expertise in ocean acoustics, to share what they have learned about noise trajectories over a longer timescale and in other areas of the world.
Below is our Skimmer-style summary of news and research articles and an interview with Chris Verlinden, a senior scientist, and chief technology officer at Applied Ocean Solutions.
Cause temporary or permanent hearing loss
Increase stress, change metabolic rates and oxygen consumption, decrease immune responses, reduce energy reserves, and decrease reproductive rates.
Cause alarm responses, decrease predator avoidance responses, compromise reproductive and offspring rearing activities, and interfere with feeding.
Inhibit Intraspecies Communication And More
Increase egg and larval mortality, cause developmental delays, slow growth rates, and increase bodily malformations.
- Decreases in shipping, cruise ship traffic, ferry traffic, whale watching tours, and recreational boating led to a significant decrease in the low-frequency noise associated with ships during the first half of 2020. Pandemic safety concerns and economic slowdowns also decreased a multitude of other activities that generate ocean noise including fishing, aquaculture, seismic exploration, oil drilling, military exercises, offshore construction, and dredging activity for at least some portion of the pandemic.
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- While relatively few specific measurements have been published to date, one early assessment of the first quarter of 2020 found that reduced ship traffic between Asia and the ports of Vancouver and Seattle (on the order of a 20% reduction from the same period of 2019) lowered noise power levels in the deepwater offshore of Vancouver Island by about a quarter and in the Strait of Georgia by nearly half. Ferry service in the region was cut after this period, so ocean noise levels at the height of the pandemic were likely even lower than the levels measured in this study.
- Another report found that median daily sound levels in Glacier Bay, Alaska, decreased by half relative to the year before due to fewer cruise ships and whale watching tours.
- In reports from other areas of the world, major ports in the northeast U.S. saw a nearly 50% decrease in ship traffic in April 2020 compared to April 2019, while ship traffic for large European ports – including Antwerp, Belgium; Le Havre, France; Lisbon, Portugal; and Rotterdam, Netherlands – dropped by a quarter that month.
- Decreases in vessel traffic during the early pandemic were not universal, however, with recreational boating increasing in some areas such as Sarasota, Florida, in the U.S.
- These slowdowns have created an extraordinary opportunity for researchers to examine how marine mammals sensitive to low-frequency ocean noise change their behavior when noise levels drop.
- Biologists in Glacier Bay, Alaska, have observed behavioral changes such as humpback whales napping, socializing, and feeding in the middle of shipping channels.
- Orcas off the coast of Scotland and Canada have been observed closer to shore than usual.
- One hypothesized change is more frequent and complex communication between individuals since ocean noise is associated with a decrease in calling behavior for whales in the region.
- The COVID-19 pandemic is reminiscent of another catastrophe – the terrorist attacks of September 11, 2001 – when a halt in world trade and traveled to dramatic reductions in ocean noise. Researchers studying North Atlantic right whales in the Bay of Fundy, Canada, found that their hormone levels related to stress decreased when vessel traffic and consequently ocean noise decreased.
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- Researchers in Monterey Bay, California, is conducting similar research in that they sampled the stress hormones of humpback whales in the bay in April and May 2020 and will compare them to samples collected when vessel traffic returns to normal. One critical difference, however, is that all boat and air traffic stopped in the days after the September 11 attacks, while offshore shipping has continued during the pandemic even as small boat and tanker traffic in the bay declined.
- The news is not all good for marine mammals, however, as pandemic-related shutdowns have interfered with annual health assessments of marine mammal populations and other marine mammal research as well as loss of funding for marine mammal conservation initiatives.
- Data on changes to ocean noise are slow to emerge during the pandemic because most hydrophones are not set up to telemeter their measurements and the pandemic has led to delays in servicing hydrophones (and recovering their data) by ship. An ongoing discovery of hydrophones that can be used for a global analysis of the effects of the pandemic on ocean sound has found the most hydrophones in U.S., Canadian, and European waters as well as the Weddell Sea with relatively few in other parts of the world.
Interview with Chris Verlinden of Applied Ocean Sciences
Skimmer: We know the pandemic led to some dramatic decreases in ocean noise in the first half of 2020, but many noise-producing ocean uses have picked back up (e.g., shipping, fishing) since then. What can you tell us about changes in the ocean soundscape from before the pandemic to now – one year in?
Verlinden: Great question. The financial shutdown associated with the COVID-19 pandemic led to a dramatic decrease in certain types of shipping activity all over the world. It is important to note that this decrease was not uniform geographically or across vessel types.
Cruise ship traffic all but disappeared during the height of the pandemic and has not yet returned to its pre-pandemic numbers. Similar reductions occurred in some passenger ferry routes where the number of vessels required to fill the needs of the community decreased during the height of the pandemic. Ferry routes, at least in the U.S., have now largely returned to pre-pandemic levels.
Recreational Fishing
Recreational fishing traffic (charters, sport fishing, deep-sea fishing, etc.) decreased dramatically in the U.S. early in the pandemic, while most commercial fishing traffic continued at its pre-pandemic levels. Traffic from military vessels remained fairly constant, as did survey and research vessel traffic.
Tanker Traffic And Container Vessel Traffic Experienced A Drop-In Rates Post 
Pandemic
Tanker traffic experienced a drop from the second half of March into April of last year but then steadily rose to pre-pandemic rates by the end of the year. Container vessel traffic experienced a similar trend in March and April 2020 but is only now starting to increase. Interestingly, bulk carrier traffic along certain areas on the U.S. West Coast decreased dramatically in March and April 2020, more than container traffic. This traffic included cargo such as gravel, chemicals, and bulk agricultural goods such as wheat and lumber. This made certain areas, such as the mouth of the Colombia River, substantially less trafficked and thus quieter than usual.
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Source: OpenChannels
