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May 9, 2016
Contact: Shelley Dawicki
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Listening to the Noise of the Deep Sea

NOAA Researchers are Building a National Ocean Listening Network

Northeast Fisheries Science Center (NEFSC) researchers recently put five powerful recording instruments along the Northeast continental shelf break to listen to the sounds made by whales, dolphins and other marine species and to monitor ocean noise in general. It’s part of a national effort to establish a network to monitor long-term changes in just how noisy the ocean is.

Five small autonomous instruments known as HARPs (High Frequency Acoustic Recording Package), were placed on the ocean floor in locations from Georges Bank to New Jersey as part of the Shelf Break Acoustic Ecology Project, funded by the Bureau of Ocean Energy Management (BOEM).

Like the musical instrument, these HARPs involve sound, but they record it rather than make it and they look very different. NOAA’s Northeast and Southeast Fisheries Science Centers are working on the project to better understand biological activity along the shelf break before planned seismic exploration off the U.S. East Coast. HARPs were developed by the Scripps Institution of Oceanography.

“All of these instruments link the U.S. Northeast Passive Acoustic Sensing Network (NEPAN), which currently monitors marine mammals and fish from the northern Gulf of Maine to the New York Bight, to a new national listening network in waters around the U.S,” said Sofie Van Parijs, head of the passive acoustics research group at NOAA’s Northeast Fisheries Science Center (NEFSC) laboratory in Woods Hole, Mass.

Van Parijs and her team placed the HARPs while working from the 76-foot Research Vessel Connecticut in late April. Researchers recovered three HARPs that had been deployed in about 900 meters (roughly 3,000 feet ) depth off Georges Bank since April 2015 and replaced them with new instruments. Two other HARPs were deployed for the first time in other locations along the shelf.

Click image to enlarge
Location of instruments for Western Atlantic Passive Acoustic Monitoring 2015-2018. Photo Credit: NOAA Fisheries/NEFSC

The five HARPs now in place are part of a network deployed from Georges Bank to Florida; three more HARPs are being placed by Scripps Institution of Oceanography off the southeast U.S. coast as part of the Shelf Break Acoustic Ecology Project. Other HARPs have been deployed off Virginia, Cape Hatteras and Florida as part of a separate project involving Duke University and the U.S. Navy.

In addition to deploying the five HARPs, researchers recovered, refurbished and redeployed a NOAA Noise Reference Station in 3,000 meters of water (roughly 10,000 feet deep). The noise reference stations listen to and characterize the ambient noise in the deep ocean as part of a much larger project being conducted by NOAA Fisheries, NOAA’s National Ocean Service, and the National Park Service called the U.S. Ocean Noise Reference Station Network.

By establishing a long-term NOAA-operated network of noise reference stations throughout the U.S. Exclusive Economic Zone, roughly up to 200 miles offshore, NOAA can monitor long-term changes and trends in the underwater ambient sound field from all sources, including human activity and animals that live in these waters.

Each station is deployed for one-to-two years before being recovered and redeployed. The data collected from the stations will provide a baseline for what ocean sound levels are now, how they are changing over time, and how human activities are impacting marine life.

Ten noise reference stations equipped with low frequency passive acoustic recorders developed by NOAA’s Pacific Marine Environmental Laboratory have been operating in U.S. waters since March 2014. There are three such buoys off the U.S. East Coast: one in Stellwagen Bank National Marine Sanctuary, one off Georges Bank between the New England Seamounts, and one off Florida on Blake Plateau.

Each station includes a set of standardized battery-powered instruments called hydrophones that listen for noise from a variety of sources. More noise reference stations are being deployed in select locations by the National Park Service, including one in the Caribbean.

“The ocean noise reference station network will provide information on what the deep sound or SOFAR (sound fixing and ranging) channel off the Northeast sounds like, what a shallower sanctuary sounds like, and how sound conditions differ between regions around the country,” said Van Parijs. “This national network will help us fill in gaps of information and enable us to monitor long-term trends and changes in the underwater sound field.”

In addition to the HARPs and noise reference station buoys, a line of low frequency marine acoustic recording units (MARUs), developed by Cornell University, are in place off the Northeast U.S. on the continental shelf to record the migratory movements and changing distribution of North Atlantic right whales and other baleen whales. The MARUs have been recording since October 2015 and will continue for three years.

Annamaria Izzi and Eric Matzen of the NEFSC’s Protected Species Branch deployed and recovered the HARPs and a noise reference station during a cruise in April 2016. Learn more about their adventure at NEFSC’s Field Science Blog.

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