Researchers Use New Tools to Measure Underwater Sound Pollution in S.F. Bay

SAN FRANCISCO (KPIX) -- A Bay Area researcher has gathered evidence that small marine vessels, such as high-speed commuter ferries and recreational boats traversing the waterways of San Francisco Bay, are adding to noise pollution underwater, which in turn could have a negative impact on whales and other mammals.

Samantha Cope, a researcher at the Anthropocene Institute based in Palo Alto, recently published her findings "Multi-sensor integration for an assessment of underwater radiated noise from common vessels in San Francisco Bay" in the Journal of the Acoustical Society of America.

Cope gathered data on more than 1,000 marine vessels over an 11-day span in 2018 in the waters south of the Richmond-San Rafael Bridge between Tiburon and Richmond. Large container and cargo ships are required to broadcast data via the Automatic Identification System (AIS), which constantly updates a ship's speed and position.

To track smaller vessels, Cope and her team of researchers built a machine dubbed the "Protected Seas Marine Monitor," or M2, an autonomous, solar-powered radar, camera and software package that uses machine learning to track, verify and identify passing ships. Data from the M2 was matched up to the corresponding underwater sound recordings of passing boats and ships.

"Using calculations, extrapolation and modeling, we can then figure out how loud the vessel was and then project that over the entire area," said Cope.

The study, which was conducted from Feb. 1 to 11, successfully identified about 60 of the watercraft as small vessels.

"Recreational craft travel wherever they want. We found that, when they travel over a larger area, that sound -- even though they're a little bit quieter than the large vessels -- they spread out all over. So, the significance is that they might be more of an impact on these animals," said Cope.

Migrating whales entering the bay to forage for food, rest or to mate will find an already-noisy environment from cargo ship traffic.

The study found "there is growing evidence that smaller vessels not required to broadcast data via the Automatic Identification System (AIS) contribute significant noise to urbanized coastal areas."

"We know from other studies in other locations that vessel noise disrupts all of these normal, typical behaviors that marine mammals do, especially the large whales. They will either stop resting, they'll stop feeding, stop socializing and maybe move to a different area in response to noise and then there are potentially all these negative cascading effects on their well-being, if they move from location to location and have these stress disruptions," Cope said.

In recent months, the San Francisco Bay has seen an uptick in dead whales washing ashore. Cope said it is unclear if the added noise from the small vessels is contributing to their deaths.

The study concluded that further research "will help determine when and where mitigation of noise and impacts from vessels is necessary and if speed or other restrictions could be beneficial."

"They've chosen to come into the bay as a stop. It's our responsibility to make sure that we're not hurting them or getting in their way when they chose to be here because we share the water with them too," Cope said.