Deep Water Plume Persists Months After BP Oil Well Blowout

Oil-eating microbes not significantly breaking down oil

20 August 2010

The Sentry autonomous underwater vehicle (AUV) aboard the research vessel Endeavor at the Deepwater Horizon oil spill site.

Over a 10-day period in late June - two weeks before the damaged seafloor wellhead was successfully capped the researchers measured a massive plume near the wellhead site.

The oil plume was approximately 1,000 meters deep, 35 kilometers long, 200 meters high and 2 kilometers wide two months after the well explosion.

The team deployed an autonomous underwater vehicle, or AUV, and a sampling device tethered by cable to their ship on the surface. Researcher Chris Reddy says what they saw was a forensic snapshot showing that hydrocarbons can move into deep marine ecosystems.

Sampling device being lowered from the Endeavor research vessel.

"Our goal was to document a plume and see what its size, shape, distribution and eventually its chemical composition. This is an important aspect because there is very little known about oil in the sub-surface."

The AUV zigzagged its way through the oil plume to measure chemicals and biological activity at various depths.

The chemical analysis reported so far showed no substantial decay in the plume, which suggests that petroleum-eating microbes were not significantly breaking down the oil. Researcher Benjamin Van Mooy says that is in part because of water temperature.