Biogeochemistry of Active Methane Seeps on the Continental Margin

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Pockmarks are errosive features found on the seabed that record the recent activity of fluid seepage --primarily gas -- through the sediments. These craters-like features have been extensively documented on continental shelves throughout the world oceans and are thought to be primarily associated with the seepage of hydrocarbons from sediment reservoirs. In spite of their common occurrence, active systems are essentially unstudied and the biogeochemical impacts of these systems on shelf sediments and coastal waters are almost completely unknown. The gas released is primarily methane (both biogenic and thermogenic) and the significance of this source to the marine and atmospheric budgets is completely unknown. It has recently been hypothesized that these systems may even plan an important role -- enhancing fisheries production on continental shelves. Following up on the pioneering studies of fluid venting along the shelf and slope of the Oregon convergent margin and upon the guidance of local fishermen, the existence of an extremely active methane vent in a pock mark on the continental shelf off Oregon has been verified water and sediment. This research is an exploratory effort to demonstrate that samples can be obtained without loss or alterations of the contained gases and analyses to identify the gases.