Noise from increased Northwest Passage shipping may impact whales: researchers

A device like this one could measure the sound level underwater at the eastern entrance to the Northwest Passage. (IMAGE COURTESY OF THE SCRIPPS INST. OF OCEANOGRAPHY)

JUSTIN NOBEL

Whales in the Northwest Passage may soon be living smack in the middle of a noisy marine highway, the question Dr. John Hildebrand wants to know is how will it affect their hearing?

“In general, the area under the ice is one of the quietest places on the planet,” said Hildebrand, an expert in marine mammal acoustics at Scripps Institution of Oceanography, in California. “But the future is, there will be less ice, we all know that. And when the ships come the expectation is that the ambient noise will go up.”

Come October, providing they get the go-ahead for their project, Hildebrand and Ian Stirling, a University of Alberta biologist, will travel to Resolute Bay to place a $30,000 underwater microphone, or hydrophone, on the bottom of the Barrow Strait.

The hydrophone will record sound, the information will be saved on a hard drive and the entire piece of equipment will run on batteries. A year later the scientists will return to pick it up and examine the data.

The goal is to get an idea of present-day sound levels in the Northwest Passage so when shipping traffic increases researchers will have a basis for comparison.

“It just seemed natural to get some sort of baseline record,” said Hildebrand. “As ships start to use that area, we can get a sense of how many decibels shipping may have raised the sound levels.”

And just how many decibels would it take to damage a whale’s hearing?

Hildebrand’s research shows that in California’s Santa Barbara Channel, part of a heavily traveled shipping corridor that connects Asia to Los Angeles, ship traffic on the order of 20 ships a day raised the ambient noise level about 20 decibels. Which means that if the Santa Barbara Channel were a workplace environment the United States Occupational Safety and Health Administration would require workers to wear earplugs.

Hildebrand explained that sound traveled differently in water than on land but the point of the analogy is striking: If whales were humans and the Northwest Passage saw as much shipping as the Santa Barbara Channel, government officials would require whales to wear earplugs.

It turns out a whale’s hearing is actually not so different from ours.

All mammals have sensors called hair cells that pick up vibration and allow us to hear. An extremely loud sound, like an explosion, can destroy the tissue of these cells and permanently damage the hearing of a whale, or human being. Just ask the hunter who rode for several hours on his snowmobile after the muffler fell off.

Moderately loud sound over a long period of time can do temporary damage to an ear. Think of how you’re hearing is dampened after a night listening to loud music.

High levels of noise over long periods of time also create stress for animals. “We know this to be true in people,” said Hildebrand. “If you subject people to high levels of noise over long periods of time you see an increase in their stress levels.”

Do high levels of noise over long periods of time stress whales? No one really knows, because not enough research has been done.

“But it’s worrying,” said Hildebrand, “because we know that people and marine mammals have very similar physiological makeup when it comes to hearing.”

Hildebrand said that before conclusions can be drawn on how shipping traffic will affect whale’s hearing, a baseline for sound levels in the Northwest Passage must be created. This is exactly what his research plans to accomplish.

Once the ice melts this research will be impossible, because the ships will already be there.

“Shipping as a means for transporting goods will go on for some time,” said Hildebrand. “And if there’s a shorter route, people will take it.”