Sea Technology

MAY 2013

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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"In this climate, developing cost-effective approaches to marine research and monitoring is crucial." (West Wareham, Massachusetts) 1-to-20-kilohertz chirp sub-bottom profler and a 10-megapixel Arecont Vision (Glendale, California) IP camera to upgrade from analog video. Having a USBL system provides additional benefts to the multidisciplinary Deep-C team. Sediment geochemistry and macrofauna are investigated by sampling with an Oktopus (Kiel, Germany) multiple corer. Attaching a USBL pinger to the corer means that core samples can be collected with precise and repeatable positioning. An initial concern about MILET was whether a passive tow body could be safely and effectively deployed at 1,000meter depths in a near-bottom mode. The test of the system was investigating the natural gas seeps that the Okeanos Explorer had detected. These bubble streams might indicate existence of natural-seep communities. MILET was deployed to search for direct evidence of discharge and telltale biological or geological evidence. The precision bathymetry of the Okeanos Explorer survey proved crucial. Gas seeps most often occur on steep-sided salt domes. Displaying the bathymetry as a backdrop in the indoor positioning system navigation program, the 35-meter research ship RV Weatherbird II was able to maneuver MILET along a precise parallel track. Cable drag in the water caused MILET to rise off the bottom on turns and required that cable payout exceed total water depth by as much as 20 percent. Despite this, operators quickly gained the confdence to "fy" MILET onto the sides of salt domes, while adjusting the winch so that toolsled altitude was maintained within the 2-to-3-meter range. The payoff came with locating chemosynthetic bacterial mats, bivalves, carbonate pavements and, at one site, multiple natural asphalt extrusions. ECOGIG While oil spilled from Deepwater Horizon potentially deposited in DeSoto Canyon via surface transport toward the northeast, oil in the deepwater plumes was carried in the opposite direction. Previous research had been conducted in the central and western Gulf because of extensive exploration and production by the energy industry, and regulations imposed by the U.S. Bureau of Ocean Energy Management. However, as with DeSoto Canyon, assessing Deepwater Horizon's impact was hampered by lack of basic knowledge. What are the rates of decomposition for oil deposited on deep-sea sediments? How are deep-sea corals and other invertebrates affected? What are the normal concentrations of oil and gas at natural seeps? To address these and many other questions, a second Gulf of Mexico Research Initiative consortium was established, employing a different research strategy. The Ecosystem Impacts of Oil and Gas Inputs to the Gulf (ECOGIG) program has targeted a few key locations, includ- www.sea-technology.com May 2013 / st 27

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