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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ECOGIG long-term observatory lander deployed at Green Canyon 600 study site. (Photo Credit: Schmidt Ocean Institute) ing the Macondo well area and prolifc natural oil seeps. At these sites, a team led by the University of Mississippi and the University of Georgia is taking long-term measurements of rates and processes related to hydrocarbon concentrations and consumption. For Deep-C, the independent variable is space across the benthic environments encompassed by DeSoto Canyon. For ECOGIG, in contrast, the independent variable is time at sites with continuous hydrocarbon inputs. The investigators have fabricated a variety of autonomous instrument systems that are deployed and precisely 28 st / May 2013 positioned to measure relevant indicators. One of the sites is a prolifc natural hydrocarbon seep located in the Green Canyon 600 lease block at 1,200 meters depth. Here, multiple streams of oily bubbles discharge from seafoor vents and rise to surface water, generating persistent oil slicks on the ocean. One issue for the investigators is whether discharge is regulated by tidal cycles or other oceanographic processes. To investigate this, ECOGIG researchers were supported by the Schmidt Ocean Institute with its fagship research vessel RV Falkor and advanced vehicles and systems. Using the ROV Global Explorer MK3, ECOGIG investigators deployed an autonomous time-lapse video camera to quantify discharge from the vent. The AquaPix VTLC recorded 15 seconds of video every 5 minutes over 60 hours, while recording temperature variability and a distinct tidal pressure signal with an RBR Ltd. (Kanata, Canada) duo logger. Preliminary results indicate distinct periodic variation in bubbling rates. A longer time constant for hydrocarbon discharges is measured using seafoor lander systems. These autonomous platforms are deployed from surface ships with a suite of instruments secured to the deck. Once in place on the bottom, the Global Explorer MK3 positions the sensor probes in www.sea-technology.com

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