FromQuarkstoQuasars

The Deepwater Horizon: Impact of the Largest U.S Oil Spill

Scott WilsonFebruary 21st 2015
(USCG Photo)
(USCG Photo)

It has been nearly five years since the largest oil spill in U.S. waters, and researchers still haven’t slowed down in their explorations of the side effects of the disaster.

Depending on your perspective, it’s either an unfortunate reality or a sort of silver lining that many big scientific questions can only be answered out of tragedy or disaster. Much was learned in the wake of the Exxon Valdez spill in Alaska in 1989; now, the focus is in the Gulf of Mexico.

The Deepwater Horizon oil spill in 2010 was the largest in U.S. history. Two hundred million gallons of crude oil were spilled into the Gulf of Mexico in the aftermath of the explosion, fire and sinking of the drill rig.

Many predictions were made about the possible environmental effects of the spill. Now, long after the searing images of flames on the water and miles and miles of sludge-covered beaches have faded from the public mind, scientists continue to study the effects and assess the accuracy of those predictions — science at work.

One of the enduring mysteries that emerged from the disaster was where around 10 million gallons of the spilled oil had ended up. Some was expected to settle to the sea floor, but since oil tends to float, that wasn’t expected to be the fate of the majority of the spill.

Many theories were developed regarding the dissipation and effects of the oil, and now, five years later, science is starting to come up with some answers.

Researchers from Florida State University believe they have located the missing oil, buried in sediment on the seafloor of the gulf, some 60 miles south of the Mississippi delta. Using a carbon 14 inverse tracer method (since the oil doesn’t contain this isotope, but normal seafloor soil does) the team conducted spot surveys and located patches they believe indicate where the missing oil landed.

The Deepwater Horizon spill from space - (NASA Photo)
The Deepwater Horizon spill from space – (NASA Photo)

British Petroleum (BP), the company primarily held responsible for the spill, disputes the findings. BP attributes the results to natural oil seeps on the seafloor, and contends that the samples collected do not support the amount of oil reported by the researchers.

Although the finding might indicate that the oil is not roaming around the Gulf in a submerged glob like the Blob, contaminating everything it touches, as some scientists worried at the time of the accident, it’s not necessarily good news — the water column contains less oxygen at the sea floor and so the microbes which might otherwise work to decompose the oil naturally will be less effective in doing so.

At the same time, on beaches where some of the oil had indisputably washed up, scientists have been closely watching microbial populations as they have moved through the cycle of degradation. Initially, the slicks killed off populations of sensitive microorganisms depending on nitrogen and sunlight which were normally present, while at the same time organisms capable of digesting compounds in the oil itself exploded.

Understanding the mechanisms behind this cycle could provide important information for responders to the next spill, according to this Science Daily article.

The various effects of the spill on marine life are still being studied as well. Recently, scientists from Oregon State University announced that sperm whales which previously fed in the spill area no longer do so, possibly indicating a larger die-off lower down on the food chain. The data agreed with findings of fish declines around two reefs which were coated with oil.

Despite their findings, scientists say that it may be another five to 10 years before the full impact of the spill is known.

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