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About the Mission 2011

Deep-water Mid-Atlantic Canyons

June 4–17, 2011

Steve W. Ross and Sandra Brooke

High resolution multibeam sonar image of a shipwreck on the continental shelf near Norfolk Canyon

Figure 1: High resolution multibeam sonar image of a shipwreck on the continental shelf near Norfolk Canyon. Image courtesy R Mather, University of Rhode Island.

This is the first cruise of a four year project to study the biology, geology and oceanography of a series of canyons off the middle Atlantic coast of the US. Of particular interest are areas of hard substrate that could support deep water coral ecosystems or other unusual habitats, such as methane seeps. Another major component of this study is marine archaeology, primarily searching for historically significant shipwrecks (Figure 1).

This new project represents a collaborative effort among the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE), Continental Shelf Associates (the BOEMRE contractor) and their academic partners, NOAA Office of Ocean Exploration and Research (provider of ship time and equipment), and the US Geological Survey (in support of BOEMRE’s energy-development responsibilities). This cruise is the first field activity for the project. The study concept, oversight, and funding were provided by the U.S. Department of the Interior, BOEMRE, Environmental Studies Program.

The NOAA Vessel Nancy Foster (http://www.moc.noaa.gov/nf/) will depart from Charleston, South Carolina on the 4th of June and head north to our study sites, which include Norfolk, Washington and Baltimore canyons off Virginia, Maryland and Delaware in water depths from 150-1000 m. The ship will return to Charleston on the 17th of June.

Target study areas

Figure 2. Major Mid-Atlantic Canyons.  Image courtesy SW Ross, UNC-W.

We are embarking on this initial cruise to provide detailed bathymetric maps of our major targets prior to the intense multidisciplinary data collection cruises in 2012 and 2013 (Figure 2).  Target areas for this project are in and around Norfolk, Washington, Accomac and Baltimore canyons. Multibeam sonar mapping and other acoustic seafloor imaging will be the primary activities during this cruise. Maps of the seafloor produced during the cruise will help guide sampling activities during future expeditions when we will use a remotely operated vehicle (ROV) to survey habitat and make collections. These sophisticated underwater vehicles are very expensive to use, and having good maps of the seafloor helps us optimize the limited ROV time. Without these maps we would be effectively searching in the dark for small targets over a vast area.

Study Areas, cruise no.1

Figure 3. Target multibeam survey boxes for this cruise, and existing multibeam sonar data (color shaded areas). Image courtesy SW Ross, UNC-W.

Some multibeam maps are already available for our study area (Figure 3), so we will prioritize areas that have not yet been mapped, such as Baltimore Canyon, or those that need better resolution, such as Norfolk Canyon.  An example of this type of detailed mapping is this small, but rugged canyon system north of Cape Hatteras, NC known as “The Point”.

Additional cruise activities will include deployment of Conductivity, Temperature and Depth (CTD) instruments, which also can measure dissolved oxygen, turbidity, pH, and florescence, and take water samples (Figure 4).  CTDs will be used extensively during this cruise to profile the water column and many locations, to collect sound velocity data used by the multibeam sonar, and to collect water samples for various analyses.

Conductivity, temperature, depth (CTD) instrument

Figure 4. Conductivity, temperature, depth (CTD) instrument. The gray tubes are Niskin water sampling bottles. Image courtesy SW Ross, UNC-W

The CTD data will be used to ‘characterize’ or describe environmental conditions, at different depths and locations along the canyon axis and the water samples will be used to analyze water chemistry and organic content.

On our transit north, we will stop at one of our previous study sites off Cape Lookout, NC to recover a benthic lander that has been collecting data on the seafloor for several months. Benthic landers are large metal platforms that have several instruments attached to measure oceanographic and environmental conditions (current speed and direction, temperature, oxygen, fluorescence, turbidity) and monthly sediment flux to the seafloor. Our final cruise objective will be to deploy a new benthic lander in the middle of the axis of Norfolk Canyon, where it will remain constantly collecting oceanographic data until we return to recover it during the next cruise.

The project is being conducted under U.S. Department of the Interior, BOEMRE, Environmental Studies Program Contract No. M10PC00100.

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