Gulf
of Mexico clean-up makes 2010 spill 52-times more toxic
If
the 4.9 million barrels of oil that spilled into the Gulf of Mexico
during the 2010 Deep Water Horizon spill was a ecological disaster,
the two million gallons of dispersant used to clean it up apparently
made it even worse – 52-times more toxic. That's according to new
research from the Georgia Institute of Technology and Universidad
Autonoma de Aguascalientes (UAA), Mexico.
30
November, 2012
The
study found that mixing the dispersant with oil increased toxicity of
the mixture up to 52-fold over the oil alone. In toxicity tests in
the lab, the mixture's effects increased mortality of rotifers, a
microscopic grazing animal at the base of the Gulf's food web. The
findings are published online by the journal Environmental Pollution
and will appear in the February 2013 print edition.
Using
oil from the Deep Water Horizon spill and Corexit, the dispersant
required by the Environmental Protection Agency for clean up, the
researchers tested toxicity of oil, dispersant and mixtures on five
strains of rotifers. Rotifers have long been used by ecotoxicologists
to assess toxicity in marine waters because of their fast response
time, ease of use in tests and sensitivity to toxicants. In addition
to causing mortality in adult rotifers, as little as 2.6 percent of
the oil-dispersant mixture inhibited rotifer egg hatching by 50
percent. Inhibition of rotifer egg hatching from the sediments is
important because these eggs hatch into rotifers each spring,
reproduce in the water column, and provide food for baby fish, shrimp
and crabs in estuaries.
"Dispersants
are preapproved to help clean up oil spills and are widely used
during disasters," said UAA's Roberto-Rico Martinez, who led the
study. "But we have a poor understanding of their toxicity. Our
study indicates the increase in toxicity may have been greatly
underestimated following the Macondo well explosion."
Martinez
performed the research while he was a Fulbright Fellow at Georgia
Tech in the lab of School of Biology Professor Terry Snell. They hope
that the study will encourage more scientists to investigate how oil
and dispersants impact marine food webs and lead to improved
management of future oil spills.
"What
remains to be determined is whether the benefits of dispersing the
oil by using Corexit are outweighed by the substantial increase in
toxicity of the mixture," said Snell, chair of the School of
Biology. "Perhaps we should allow the oil to naturally disperse.
It might take longer, but it would have less toxic impact on marine
ecosystems."
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