floridaoilspilllaw.com | Study finds massive flux of gas, in addition to liquid oil, at BP well blowout in Gulf, PhysOrg, February 13, 2011:

A new University of Georgia study that is the first to examine comprehensively the magnitude of hydrocarbon gases released during the Deepwater Horizon Gulf of Mexico oil discharge has found that up to 500,000 tons [1 billion pounds] of gaseous hydrocarbons were emitted into the deep ocean. …

[Ira Leifer of the University of California-Santa Barbara] added that some of the larger gaseous hydrocarbons documented, such as pentane, have significant health implications for humans and potentially for marine life.

[UGA Professor of Marine Sciences Samantha Joye] cautioned against assuming that microbes will rapidly consume the gases released from the well. Undoubtedly, the methane is a feast for them, Joye said, but she also noted that the microbes need nutrients, such as nitrogen, copper and iron. These nutrients are in scarce supply in the Gulf’s deep waters, Joye said, and once they are depleted the microbes will cease to grow—regardless of how much methane is available.

Magnitude and oxidation potential of hydrocarbon gases released from the BP oil well blowout, Nature Geoscience, February 13, 2011:

Gaseous hydrocarbons turn over slowly in the deep ocean, and microbial consumption of these gases could have a long-lasting impact on oceanic oxygen levels. …

Analysis of water around the wellhead revealed discrete layers of dissolved hydrocarbon gases between 1,000 and 1,300 m depth; concentrations exceeded background levels by up to 75,000 times.

We suggest that microbial consumption of these gases could lead to the extensive and persistent depletion of oxygen in hydrocarbon-enriched waters.