Microbial Oxidation of Natural Gas Emanating from Coal Oil Point Seep Fields

The hydrocarbon seep field at Coal Oil Point, off the coast of Santa Barbara, California, releases > 10¹⁰ g of thermogenic gas each year.  Gas emissions from Coal Oil Point are composed of methane, ethane, propane, and butane, which have consequences if released into the atmosphere.  Even though the seeps are at water depths of only 5-80 m, much of the gas dissolves and contributes to a plume that is transported by ocean currents. While hydrocarbon plumes can support bacterial respiration, resulting in the removal of hydrocarbon gas from the water, the magnitude of gas consumption in marine environments is poorly understood. To track respiration rates in these plumes, novel ³H-ethane, propane, and butane tracers were synthesized using Grignard reagents and tritiated water. Tracer validation experiments show that ³H tracers are more sensitive than previous methods using stable isotope tracers, making this tracer technique preferable in natural systems. Preliminary samples collected during September 2011 aboard the R/V Atlantis, show ethane, propane, and butane consumption are readily inducible on a timescale of days. A higher resolution sampling of the Coal Oil Point plume is scheduled for summer 2012.

[This research was supported by the National Science Foundation]