On any given day, the waters of Puget Sound are bustling with the traffic of container ships, ferries, and every vessel in between. However, recent work from UW researchers has found that noises from the ships may harm marine life.
UW graduate student Christopher Bassett and his colleagues have been monitoring data from instruments placed in the waters of the northern Admiralty Inlet between Port Townsend and Fort Casey State Park on Whidbey Island. The researchers found that 90 percent of the time, they were picking up signals from nearby marine vessels. These noises routinely exceeded the 120-decibel level the federal government has suggested is harmful to surrounding marine life.
“Due to high densities of vessel traffic in Puget Sound, it’s a noisy place,” Bassett said.
Bassett’s group began its work in April, 2009, as part of a site characterization for a proposal by the Snohomish County Public Utility District (PUD) to install underwater turbines in Admiralty Inlet to harness tidal power.
Dr. Brian Polagye, a research assistant professor in the Department of Mechanical Engineering and co-director of the Northwest National Marine Renewable Energy Center, said in the case of turbines, noise levels were minimal.
“Once you get a few hundred meters away from the turbines, the probability that a marine mammal will hear them drops to less than 20 percent,” Polagye said, adding that mammals hearing the noises depends on several factors, including the vessel type and amount of ambient noise.
However, the sound emitted by turbines and that emitted by a large container ship are two different types of sound.