Believe it or not, the Deepwater Horizon oil spill was even worse than previously thought

After the Deepwater Horizon explosion in the spring of 2010, oil
poured into the Gulf of Mexico for nearly three months straight,
resulting in the worst offshore oil spill in U.S. history. More
than 200 million gallons of light crude flowed into the sea,
marine life

Ten years later, scientists are still uncovering new facets of
the disaster and its aftermath. A
published Wednesday from researchers at the University of
Miami found that fisheries closed by federal and state agencies
after the spill only accounted for about 70 percent of the actual
extent of the toxicity that emanated from the drilling platform.
The closures were based on satellite images of so-called surface
slick — the visible oil on the surface of the water. This metric
was ultimately not sensitive enough to capture lower concentrations
of oil that nevertheless were still harmful to animals.

“It’s a pretty interesting finding, and it shows that the
surface slick is not a sufficient indicator of the real footprint
of where the damage is occurring,” said Cameron Ainsworth, a
fisheries oceanographer at the University of South Florida who was
not involved in the study but has collaborated with its authors on
related research.

Igal Berenshtein, a postdoctoral fellow at the University of
Miami and lead author of the new study, said he originally set out
to look at the effect of fishery closures on communities in the
Gulf. One of the first things he did was run a model that his
advisor, Claire Paris-Limouzy, developed that mapped where oil
would have travelled after the spill, based on the specific
conditions in the Gulf at the time. When he compared that map to
the fishery closures, the results were intriguing: The model showed
that oil likely traveled well beyond the bounds of the fishery

When Berenshtein pored over past studies, the literature
confirmed that oil had in fact been detected as far as the waters
off the west coast of Florida, the Florida Keys, and Texas. That
led to the question: Was the oil that spread beyond the fishery
closures in high enough concentrations to be toxic to plant and
animal life? And if so, what was the line between the toxic oil
that satellites could detect, and the “invisible” but still
toxic oil that they couldn’t?

One of the reasons for the discrepancy is the way that
“toxicity” was being measured by fishery managers. “Until
recently, the estimated satellite detection threshold was roughly
equal to the estimated level of concern,” the paper’s authors
write. But recent studies have found that organisms can be harmed
at much lower concentrations due to a phenomenon called
photo-induced toxicity.

After the spill, as oil floated around in the Gulf, it was
exposed to ultraviolet radiation from the sun. When UV light
interacts with the hydrocarbons in oil, it can produce new chemical
compounds that can be more dangerous than the oil itself —
especially to fish larvae and other young creatures. When the
authors took this effect into account, they found that the oil
concentration capable of killing many Gulf species is lower than
what satellites can detect.

While satellite captures will remain essential for these kinds
of calculations, according to Berenshtein, the study presents an
additional framework that emergency managers can use to measure and
account for the oil that’s “invisible” to satellites but
still toxic to marine life. Accurate assessments of offshore
drilling risk — and the effectiveness of emergency action after
deadly spills — may benefit from the added precision this method
can provide.

This story was originally published by Grist with the headline
Believe it or not, the Deepwater Horizon oil spill was even worse
than previously thought
on Feb 14, 2020.

Source: FS – All – Science – News
Believe it or not, the Deepwater Horizon oil spill was even worse than previously thought