In the underwater world, where hearing can be more important than sight, whales are being bombarded by a cacophony of sounds, which started cluttering up their lives when the first steamships were launched into the ocean.
Now, after 200 years, people are beginning to care about the kinds of noise imposed upon marine mammals and other creatures. To a limited extent, research can now answer this important question: How are humans affecting marine life with noise coming from our ships and boats, our ocean exploration and construction, and our military exercises.
It is time to think about how we can apply new scientific knowledge in a more meaningful way than current regulations, which depend on putting a “safe” distance between one vessel and one whale.
A month ago in “Amusing Monday,” I featured the music of Dana Lyons, who wrote a song about sound from the perspective of the whales. The song got me to thinking about how the sailing ships of yesteryear must have been so much more pleasant for the whales — assuming, of course, that they weren’t whaling ships.
Scott Veirs, an oceanographer, joined forces with his dad, physicist Val Veirs, to operate a hydrophone network based in the San Juan Islands, where they study the sounds of whales, ships and anything else that makes sounds in the waters of the Salish Sea.
“We are trying to get a statistically significant characterization (of sound),” Scott told me. “For me, the question is: Does this make a difference for certain species? To be honest, I’m seeing lots of evidence in the emerging literature that ship noise really does make a difference.”
Scott and Val, along with acoustics expert Jason Wood, recently published a research paper in the journal “Peer J.,” in which they describe their acoustic encounters with more than 3,000 ships passing by their hydrophones. Through careful calibration of their instruments, they were able to calculate sound levels at the source — which can tell us which ships and boats produce the most noise before attenuation of the sound through the water. Check out the news release, or read the entire article.
It has long been known that cargo ships and other large vessels produce low-frequency sounds that can travel great distances in seawater. That adds to an overall background noise that seems to be increasing over time. For baleen whales, who communicate with lower-frequency sounds, this changing soundscape could be something like the difference between a person living downtown in a busy city and a person living in the country.
In an interesting but unplanned study after the 9/11 attacks of 2001, researchers were able to show that right whales in Canada’s Bay of Fundy had lower stress hormone levels immediately after the attacks. That’s when ship traffic — and noise — were significantly lowered. The findings were limited to the short time frame that ship traffic diminished, but the researchers were fortunate that fecal samples from another study could be used to measure stress hormones before and after 9/11. Review the paper: Evidence that ship noise increases stress in right whales.
It was not a big surprise that large ships can affect baleen
whales, but Scott and his colleagues were able to show that large
ships produce not only low-frequency sounds but also high-frequency
sounds in the hearing range of killer whales.
“The noise does extend up into the range where whales hear well,” Scott told me, “but that does not answer whether it matters to killer whales.”
He said the challenge for orcas is to hear the reflection of high-frequency clicks sent out by an orca to locate chinook salmon and other prey. The echolocation clicks are loud as they leave the whale, but the return signal they are attempting to hear can be faint unless the fish are very close, Scott said. If other high frequency sounds, such as from nearby boats, interfere with their hearing, then the whales may struggle to locate their prey, he noted.
“My greatest concern is how much a single container ship might decrease the range that a killer whale would be able to hear the echo,” Scott said. “The impact in terms of decreasing their foraging range is really kind of scary.”
Studies of various ships might identify what is causing the high-frequency sounds and lead to a technological solution to the problem, Scott said. Military ships are designed to be quiet, and some of that technology could be transferred to commercial vessels. If the noise from just 10 percent of the noisiest vessels could be reduced, it could lead to a significant improvement in the noisy ocean.
The question of how much high-frequency noise reaches the killer whales was the focus of a study conducted by researchers from the University of Washington and NOAA Fisheries. Researchers used suction cups to temporarily attach digital acoustic recording tags, or d-tags, to killer whales to measure the level of sound. They also used laser-positioning equipment operated from a research boat to measure the size, speed, location and type of vessel emitting the noise.
“The goal was to understand this missing but assumed link between what we see at the surface and what the whales experience at depth,” said Juliana Houghton, a recent UW graduate and lead author of the study, who was quoted in a UW news release.
A key finding was that the number of propellers on a vessel influenced the sound volume, but the most important factor was the speed of the vessel — with higher speeds producing significantly more high-frequency noise. The findings were published in the journal PLOS ONE.
Taking these and other studies together could help chart a path toward quieter vessels, less noise around whales and ultimately a better outcome for marine mammals dependent on underwater communication and echolocation.
Port Metro Vancouver in British Columbia has taken these ideas one step further with a hydrophone listening station installed in the inbound shipping lanes in the Strait of Georgia north of the U.S. border. The listening station is part of a program called Enhancing Cetacean Habitat and Observation (ECHO). The listening station will monitor the noise of identified ships passing through. See news release from the port.
The video below shows the deployment of the listening station in the Strait of Georgia in British Columbia.
From what I know about the system, it could potentially lead to an individual sound profile for each ship entering Canadian waters, and authorities could investigate whether slowing certain vessels could reduce noise for whales in the area.
“The ECHO program’s long-term goal is to develop mitigation measures that will lead to a quantifiable reduction in potential threats to whales as a result of shipping activities,” Duncan Wilson, vice president of corporate social responsibility at Port Metro Vancouver, said in an op-ed piece in the Vancouver Sun.
“These mitigation measures may include incentives for the use of green vessel technology, changes to operational activities of ocean-going vessels, a certification program for quiet vessels, and/or the development of noise criteria for vessels entering the port,” he added.
A 2013 report by World Wildlife Fund–Canada (PDF 2.6 mb) makes the case for developing tools to better manage noise. The 96-page report, which came out of a 2012 workshop on ocean noise in Canada, concluded that the ability to profile individual ships could lead to these ideas for reducing noise:
- “Use existing data on noise output from different sizes and classes of vessels, and establish percentage criteria below which ships should fall. Vessels above the criteria would face pecuniary consequences, e.g., higher port fees…
- “Shipping noise should not be allowed to reduce whale communication space beyond a certain percentage … Masking is a significant threat to marine animals.
- “Establish a cumulative noise exposure level…, rather than only maximum event-based exposure criteria for individual populations.
- “Develop a report card system that identifies the noisiest 10% of vessels passing over a noise monitoring station. In the absence of legislation, letters could be sent to vessel owners advising them of their noisy ships, and a list of worst offenders could be published. Letters could also be sent to the owners of quiet ships, congratulating them on their reduced contribution to the soundscape.
- “Ports could adopt maintenance requirements for noisy ships, as poor vessel maintenance is the source of extraneous noise on approximately 10 percent of merchant ships.
- “A mandatory phased-in program could be established to incentivize quietening technologies for retrofitted vessels. Proposed new projects could require quietened ships.”
Although the United States began regulating the effects of ocean noise earlier than most countries — as early as the 1980s — U.S. agencies have been slow to keep up with the best available science, according to Michael Jasny of the Natural Resources Defense Council, who wrote a chapter in the WWF report,
Be honest about estimating effects: U.S. sound thresholds for marine mammals assume that 120 decibels of “continuous” noise or 160 decibels of “intermittent” noise have an adverse behavioral effect, while noise above 180 decibels is considered injurious. But these numbers fail to account for differences in species, bias in observed impacts and masking effects. This makes the thresholds “outdated” and “insufficiently conservative.”
Think cumulatively: Regulators and managers should look beyond the effects of a single sound exposure to the effects of noise over time on the population of animals from all sources of noise.
Evolve beyond the near field: The traditional approach has been a “safety zone,” in which sound sources are powered down when marine mammals get within a specified range. The U.S. has begun to move beyond this simple idea to habitat-based management, including area closures for important habitats when marine mammals are likely to be present. Also under review are technical alternatives to reduce noise from ships, airguns (used in seismic studies) and pile-driving equipment.