What happened to the oil in the Gulf of Mexico?

There is controversy over how much of the approximately 4.9 million barrels of oil spilled from the Deepwater Horizon well remain in the Gulf of Mexico.

A team from the National Incident Command, the Department of the Interior, and the National Oceanic and Atmospheric Administration (NOAA) calculated an “oil budget” for the spill. “The oil budget calculations are based on direct measurements wherever possible and the best available scientific estimates where measurements were not possible.” The report is without any documentation. The results are shown in the graphic below.

gulf-oil-budget

The Administration announced that much of the oil was eaten by bacteria. A report in Science disagrees with the government estimates:

“Oceanographers from the Woods Hole Oceanographic Institution (WHOI) in Massachusetts surveyed the gulf around the BP well from the research ship Endeavor from 19 to 28 June, a period of heavy flow. Led by oceanographer Richard Camilli, the team deployed an array of instruments on both a cable-lowered water sampler and an autonomous underwater vehicle. All told, the instrumentation made more than 57,000 separate chemical analyses of a plume southwest of the well.

“The first thing that the researchers noticed was that the plume wasn’t quite as massive as many news reports had made out. The plume surveyed by Endeavor was only 200 meters thick and about 2 kilometers wide. Although plenty of oil was flowing from the ruptured well, it didn’t look much like an underwater oil slick. The team’s camera picked up a yellowish fog half a kilometer from the well, and water samples farther from the well did not look or smell like oil. “The plume was not a river of Hershey’s syrup,” says marine geochemist Christopher Reddy of the WHOI group.

“The plume did, however, contain more than 50 micrograms per liter (about 0.05 parts per million) of a group of particularly toxic petroleum compounds that includes benzene, the team reports online today in Science. That amount of benzene-related petroleum compounds is roughly consistent with the 1 to 2 parts per million of total oil reported in plumes by some other researchers.

“On the microbe front, the WHOI team also found differences. A report released last week by a group of federal agencies led by the National Oceanic and Atmospheric Administration stated—without documentation—that early signs show the oil is “biodegrading quickly.” Not so in the southwest plume in late June, the WHOI researchers found. Their measurements of oxygen dissolved in seawater, which bacteria consume as they feed, showed that microbes had not appreciably degraded the oil during its first 5 days out of the well.”

The New York Times opines “So far, scientific information about the gulf has emerged largely from government reports and statements issued by scientists. Many additional research papers are in the works, and it could be months before a clear scientific picture emerges.

“The slow breakdown of deep oil that Dr. Camilli’s group found had a silver lining: it meant that the bacteria trying to eat the oil did not appear to have consumed an excessive amount of oxygen in the vicinity of the spill, alleviating concerns that the oxygen might have declined so much that it threatened sea life. On this point, Dr. Camilli’s research backs statements that the government has been making for weeks.”

More disagreement with government estimates comes from University of Georgia researchers. They claim that as much as 79% of the oil spilled from the Deepwater Horizon well could in fact remain at large in the Gulf of Mexico, where it still poses a threat to the marine ecosystem. The graphic below shows their oil budget.

georgia-oil-budget

Only time and more research will tell who’s estimate is closer to reality.

The Gulf oil spill is estimated at 4.9 million barrels (about 206 million gallons). Let’s put that in perspective.

“A 2003 research paper by Kvenvolden and Cooper in Geo-Marine Letters estimated that natural seeps dump 140,000 metric tons of crude oil into the Gulf of Mexico each year –over one million barrels of crude per year. In fact, the authors estimate that 47% of all the petroleum found in the sea is from natural seeps – the largest single source, ahead of airborne pollution, ground runoff and drilling/shipping accidents,” says the Energy Tribune.

The Woods Hole Oceanographic Institution says there is an oil spill every day at Coal Oil Point, the natural seeps off Santa Barbara, California, where 20-25 tons of oil (about 7,500 gallons) have leaked from the sea floor each day for the last several hundred thousand years (at least 800 billion gallons). The Woods Hole scientist say that some oil is degraded by microorganisms and some evaporates, but most of it winds up in the ocean sediments. Could a similar process have produced the Canadian tar sands?

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2 comments

  1. Good article!

    I was curious about all of the oil that went down with the thousands of ships sunk during WWII. There are some sites on the internet that have explored that topic. There were many oil tankers as well as warships that may still have oil in their tanks. There are also many ships from WWI.

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