A gas-capture buoy for measuring bubbling gas flux in oceans and lakes

The design, calibration, and deployment of a buoy and gas-capture assembly for measuring bubbling gas flux in oceans and lakes are described. The asse mbly collects gas in a chamber while continuously measuring the position of the gas-water interface that forms as gas accumulates. Interface position is determined from the differential pressure between the chamber and ambien t seawater. A spar buoy provides flotation and stability to reduce vertical motion from surface waves. The gas-collection assembly and spar, referred to as a flux buoy, is suitable for deployment from small boats under condit ions of light wind and small waves. The flux buoy is being used to determin e the spatial distribution of natural hydrocarbon seepage off the south-cen tral California coast. Hydrocarbon seepage from continental shelves may be an important source of atmospheric methane.