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Sonar Survey of Sea-Floor Habitats Southeast of Santa Barbara, California
From August 7 to 27, U.S. Geological Survey (USGS) personnel surveyed approximately 75 km2 of the continental shelf southeast of Santa Barbara, using interferometric sonar, which collects both bathymetric and acoustic-backscatter data. Similar to sidescan-sonar data, acoustic backscatter yields information about the sea-floor surface, allowing researchers to distinguish, for example, between areas of soft mud and hard rock and to image manmade structures, such as pipelines. The survey was funded by the Minerals Management Service (MMS), which will use the data for various purposes, including monitoring oil and gas activity, assessing biological resources, locating natural tar seeps, and monitoring archeological resources. A similar survey, also funded by MMS, was conducted in deeper water to the southeast in August 2004 (see "Mapping Benthic Habitat Around Oil Platforms in the Santa Barbara Channel, California" in Sound Waves, November 2004). The recent survey was conducted in two legs. Pete Dartnell, Jamie Conrad, Mike Boyle, and Gerry Hatcher participated in the first week-and-a-half-long leg, and Guy Cochrane, Nadine Golden, and Mike Boyle crewed the second leg, along with USGS volunteer Margie Boyle. Before the cruise, Kevin O'Toole manufactured hardware for mounting the interferometric sonar on the Channel Islands National Marine Sanctuary's research vessel Shearwater. For the first few days of each leg, Andy Stevenson provided onboard training in processing the interferometric-sonar data, a task which the scientists conducted daily during the survey.
The final 3 days of the cruise were spent collecting video footage in selected areas to groundtruth each type of pattern observed in the sonar data—smooth, featureless images that might indicate a muddy bottom, for example, or sharp contrasts that might indicate rocky habitat. University of California, Santa Barbara (UCSB) biologist Donna Schroeder participated in video surveying of bottom habitat and benthic species. Rocky sea floor was mapped north of the platforms along an east-west-trending bathymetric ridge. This type of sea floor particularly interests MMS because it supports diverse communities of marine organisms, including rockfish, an important resource for commercial and recreational fisheries. The original goal for the cruise was to survey the area around shallow-water oil platforms southeast of Santa Barbara, and that goal was readily accomplished. Good weather and reliable equipment gave us the opportunity to collect additional data southeast of Carpinteria for a USGS coastal-erosion study being conducted in cooperation with the city of Carpinteria and the U.S. Army Corps of Engineers. Headed by Patrick Barnard, that study will eventually include bathymetric surveys in nearshore waters and the surf zone, high-resolution mapping of the beach, and deployment of offshore instruments to measure waves and sediment transport.
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in this issue:
Sonar Survey of Sea-Floor Habitats Drilling for Submarine Ground Water
USGS and Elementary School Receive Mayor's Top Apple Award
Chinese Delegation Visits USGS to Discuss Gas-Hydrate Studies
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U. S. Department of the Interior | U.S. Geological Survey
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