Oil threat to Gulf life in deep sea little known.
U.S. officials approved the use of oil dispersant - a type of oil soap which includes toxic chemicals - on oil on the surface of the water, and a mile below the surface at the ruptured BP well, in an effort to protect beaches and marshes along the coast, officials said.
Dispersants break up oil into microscopic droplets, which can be more easily degraded by micro-organisms and decomposed by sunlight near the surface, officials said.
How the mix of oil and oil dispersant far below the surface affects sea life was the focus of experts testifying before lawmakers in Washington on Wednesday. So far, official estimates show 1.8 million gallons of dispersants were released into the Gulf as part of the spill response. An estimated 172 million gallons of oil escaped from the once out-of-control busted well into the Gulf about 50 miles from Louisiana's coast.
"Very little is known about deepwater ecology, and consequently, very little is known about the toxic and oxygen depleting impacts of dispersant use at depth," Edward Overton, a professor at Louisiana State University, told Senators of the Environment and Public Works Committee.
"Oiling of grassy marshes is generally considered to cause more environmental damage from an oil spill, so offshore dispersant use is normally considered the 'lesser of the two evils,'" Overton said. "Offshore dispersant use represents a decision by responders that damage from on-shore oiling will be more severe than damage to offshore environments."
Paul Anastas, an administrator within the Environmental Protection Agency, said that levels of dissolved oxygen in the water had not approached levels of concern to aquatic life and no excessive deaths in microscopic organisms had been observed by monitors so far.
The released oil could still pose a threat, one expert said.
"Moving oil below the seasurface presents significant challenges to the organisms residing in this habitat," said David Smith, a professor of oceanography at the University of Rhode Island. "Impacts will be less noticeable, but could be as devastating as oil washing ashore."
While microorganisms are expected to degrade most of the oil at the surface, "we know nothing of how they do so in the deep-sea," he said, noting that there are "far fewer microorganisms in the deep-sea compared with the surface." The dispersant use could also lead to contamination of the seafloor, he said.
Jane Lubchenco, the head of the National Oceanographic and Atmospheric Administration, told reporters in the White House at a separate briefing Wednesday that the agency has no evidence of oil being at the sea floor despite ongoing monitoring by research vessels.
"It's primarily between 3,300 and 4,300 feet [below the surface] as a very diffuse cloud that is in concentrations that diminish as you go away from the wellhead," she said.
Endangered species and a type of fish whose numbers have already been declining may have been affected, said Prof. Ronald Kendall of Texas Tech University.
He warned about "subtle indirect effects of dispersed oil on the environment" for the young of a species known as Kemp's Ridley sea turtles. The impact of the mix on seaweed could have "serious negative impacts" for the turtles, which may use the plants for rest and food, he said.
"We may not see oiled, dead Kemp's Ridleys, but their population abundance could be imperiled by subtle indirect effects of dispersed oil on the environment," Kendall said.
The mixture could also be toxic to endangered sperm whales and could disrupt the summer Gulf birthing period, he said. Bluefin Tuna, which has seen big declines in recent decades, may have been impacted in its larval phase during its March to May spawning period, he added.
Lubchenco said that there was "potential concern" for Bluefin Tuna at the microscopic juvenile stages that would grow into fish "many years from now."
U.S. officials allowed BP to use dispersants in Gulf of Mexico waters soon after the Deepwater Horizon oil rig disaster with the reasoning that doing so was better than leaving the oil alone.
"Environmental tradeoffs are associated with the widespread use of large quantities of dispersant," Anastas said at the hearing. "However, dispersants are generally less toxic than oil; they reduce risks to shorelines, and degrade quickly over several days to weeks, according to modeling results."
The dispersant being used for the current spill, which goes by the brand Corexit 9500, is a combustible liquid that contains chemicals that allow it to both dissolve in water and dissolve oil. Its manufacturer, Nalco, warns in its product description that it should be kept away from the eyes and skin and poses an "acute" human health hazard.
On May 26, U.S. officials ordered BP to reduce the dispersant's use by more than 75 percent, citing the unknown effects on the environment using such a large quantity and began conducting a study comparing the toxicity of various types of dispersants.
Anastas said that efforts to find less toxic dispersants had not been successful.
"The dispersant used in response to the Gulf oil spill, Corexit 9500A, is generally no more or less toxic than the other available and tested alternatives," Anastas said.
BP had been using the chemical with government approval since the start of the spill until July 15 when a new cap was installed on the well that blocked leaking oil.
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|Publication:||International Business Times - US ed.|
|Date:||Aug 5, 2010|
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