One year after the Deepwater Horizon blow-out began the worst oil
spill in US history, scientists continue to investigate the effects
of the oil and its residues.
A year after the worst off-shore oil spill in US history began,
scientists continue to sample the sea floor and comb beaches and
marshes in an attempt to track the fate of oil that spewed for
nearly three months from the Deepwater Horizon blow-out.
But the emphasis has long since shifted from debates over a
simple "Where's Waldo" kind of accounting, to measuring how the oil
degrades with time in various environments, and the effects the
remnant chemicals can have on the habitats they encounter.
The effort should give restoration teams a better sense of where
they need to focus their work. It should also provide benchmarks to
more effectively gauge the resilience of land and ocean organisms
after their assault by oil and the dispersants used to break up
The BP spill "gave nature a stress test," says marine scientist
Christopher Reddy of the blow-out's environmental aftermath. In
trying to assess how nature is responding, it's vital to know how
the chemical agents responsible for the stress change over time, he
Accounting for the oil
Shortly after BP capped the blow-out on July 14, and oil stopped
flowing, federal officials released a checkbook-like accounting of
the oil's fate. But it proved controversial.
The uncertainties in some of the categories were large. The
report had not undergone a rigorous peer review. Indeed, the numbers
were never meant to represent a rigorous, definitive accounting,
according to a white paper prepared by the staff of the National
Commission on the BP Deepwater Horizon Spill and Offshore Drilling.
Instead, the results intended to give the National Incident
Command an general idea of how to allocate clean-up resources.
But it prompted Carol Browner, head of the US Environmental
Protection Agency, to publicly declare that nearly 75 percent of the
oil was gone.
In fact, the balance sheet showed that only about 25 percent of
the oil could safely be categorized as "gone" - either from
skimming, burning, or being loaded onto tankers.
Chemical dispersants, evaporation and natural degradation had
taken their own toll on nearly half of the oil released, according
to the document, but scientists pointed out that while such
processes can reduce the volume of hydrocarbons in the ocean, it
also can leave what's left in a form that takes far longer to break