Researchers installed a water monitoring sensor to the hull of a ferry in order to gain insight into the circulation of the Puget Sound.

Understanding how water flows though the sound's channels could help researchers learn more about the local marine environment, a University of Washington news release reported.

"Admiralty Inlet is the gateway between the ocean and Puget Sound,"Jim Thomson, an oceanographer with the UW Applied Physics Laboratory, said in the news release. "We are measuring the flow through that gateway."

The researchers are especially interested in processes that bring low-oxygen water up from the deep ocean. Lack of oxygen has been linked to fish kills in the area; the researchers would like to determine if regulating sewage runoff would prevent the problem.

"Under certain conditions deep water from the ocean will come up and sneak into Puget Sound and possibly contribute to low oxygen levels. Right now there is limited data, so it's hard to say when or how much this happens," Thomson said. "We really are an urban water system, but there's also this very natural process connected to the ocean that changes our water quality."

The researchers had a seafloor sensor installed for four years, but this device could only see a small piece of the picture.

"Monitoring of Puget Sound is important because it helps us understand long-term trends and changes over time," Carol Maloy, a marine scientist at the state Department of Ecology, said in the news release. "Monitoring helps us understand if changes are natural or human-caused. If changes are human-caused, perhaps there are steps we can take to reverse problems."

The ferry sensor is an Acoustic Doppler Current Profiler. It sends sound waved through the water to take its readings. Particles in the water reflect the sound back to the sensor in order to determine the directions and speed of the sound.

The ferry sensor will do the work of what would have been 32 sensors placed along the three-and-a-half mile-long area of the sound.

"This is an example of a creative and cost-effective collaboration helping us better understand the complex marine ecosystem of Puget Sound," Ken Dzinbal of the Puget Sound Partnership, which is a partner on the project, said in the news release.

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