Noise From Large Ships Disturbing Pacific Northwest Orca WhalesBy Russell Westerholm
The noise large ships make underwater is disturbing endangered orca whales in the Pacific Northwest.
"These ships are not only prevalent, but quite loud compared to other sources of noise in the ocean," Scott Veirs, an oceanographer who lead a study on the matter published in the journal PeerJ, told TakePart.com. "Ships are dominating the soundscape.
"As an endangered species, the killer whales will be at the top of our list," he said. "But we also want to look at fish, invertebrates, and the many other marine mammals we have. Some of them are also high-frequency specialists, such as white-sided dolphins and Dall's porpoise."
The noise the ships the make appears to be interfering with the endangered whales' communications with one another. The sound also seems to be messing with their hunting.
"The most subtle sound they are probably trying to hear is the sound of their echolocation clicks bouncing off a salmon," Veirs said. "Like bats, they're listening for very faint echo from their prey."
For their study, the researchers measured the sound more than 1,500 large ships made using underwater microphones.
"The study is unique because it estimates the source levels of larger populations and more classes of ships than in previous studies," read a press release detailing the study. "Overall, container ships exhibited the highest median source levels (at all frequencies below 20,000 Hz). Military vessels had some of the lowest levels, suggesting that transfer of quieting technology to the commercial sector could be a successful noise mitigation strategy.
"The study shows that another potential way to reduce noise pollution is to simply slow down. The data suggest that, on average, each reduction in a ship's speed by 1 knot could reduce broadband noise levels by 1 dB."