Scientists Try to Gauge Potential Long-Term Environmental Impact

ROBERT LEE HOTZ

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A brown pelican flies over oil soaked containment booms near the Pelican Rookery off of Queen Bess Island, near Grand Isle, La.

Dissolving into patches, sheens, tarballs and microdrops, the oil slick spreading from BP PLC's damaged well in the Gulf of Mexico is creating a unique mosaic of potential hazards that has marine biologists, health experts and wildlife activists scrambling to understand its potential impact.

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It is a spill like no other, taking place a mile or so under water and spreading in layers of more-shallow water and on the surface, unlike more-common spills that occur on the surface alone. The oil and dispersant chemicals used to dissolve it are potent variables in the biochemical equation of life across the Gulf, said several marine biologists, oceanographers and wildlife experts are working to understand how large or long-lasting the region's problems may become.
"This is a three-dimensional spill," said Columbia University oceanographer Ajit Subramaniam. "The physics, the chemistry and the biology action are very different when you have oil released from below."
The well's location some 50 miles off Louisiana's coast, in an area of extensive marine diversity, has heightened scientists' concern about potential damage. Around the spill zone, marine researchers have cataloged 1,728 species of plants and animals, such as crabs, shrimp, marine mammals and sea turtles. Of those, 135 are unique to the area and 74 species are endangered, according to a comprehensive marine survey.

The oil spill is giving marine scientists a rare opportunity to seek answers to some fundamental questions .

Life in the Gulf evolved in a world of oil: In addition to the 4,000 commercial oil platforms operating in the Gulf, there are 1,500 or so natural seafloor seeps that leak about 15 million gallons of oil every year. However, the seepage amounts to nowhere near the amount of oil currently gushing into the environment.
Ideally, the scientists said, eddy currents may continue to sequester much of the oil offshore, where naturally occurring bacteria can safely break down the toxic petroleum compounds.
Under the worst-case scenario, however, the oil spill could fundamentally alter the marine chemistry of the Gulf, making it less hospitable to the life that makes the region a valuable commercial fishery and damage—perhaps irreparably—much of the marine life that gives the area its unique natural character.
"We've thrown a monkey wrench into that ecosystem," said marine oil-spill expert Chris Reddy at the Woods Hole Oceanographic Institution in Massachusetts. "There are uncertainties about the long- and short-term impacts."
Under the best-case scenario, the effects of so much oil may taint Gulf fisheries for only a season. But even brief exposures to the oil could further weaken species already listed as threatened or endangered.
"Depending on where the oil spill moves and when, it has the potential to harm five different species of sea turtles, all of which are listed as threatened or endangered," said marine scientist Elizabeth Griffin Wilson at Oceana, an environmental group opposed to offshore drilling.
"You could end up changing the ecosystem completely," said Columbia University marine biologist Andrew Juhl, who studies marine pollution. "The things that tend to live in polluted areas are not the sorts of things we like."
Meanwhile, the approaching hurricane season is compounding the uncertainty because the spill's effects could be curtailed or worsened by storms, depending on their strength, duration and direction.
"The big jokers in the deck now are hurricanes," said marine ecologist Thomas Shirley at Texas A&M University. Forecasters have predicted as many as 14 major hurricanes in the coming season.
Hurricane winds could whip up waves that would more rapidly dilute and disrupt surface slicks so they could be digested by natural bacteria. However, a hurricane-driven storm surge could drive oily saltwater deep into freshwater marshlands, smothering plants and killing wildlife far from the wellhead.
"If that water is carrying oil as well as salinity, there is a double whammy," Dr. Shirley said.
Until it was partly contained, the well gushed as many as 50,000 barrels a day into the Gulf, according to the newest calculations by government and university experts. All the while, low concentrations of that oil spread on subsea currents in billows of oil drops too small to see, as many as 45 miles from the well site.
By week's end, crews had sprayed about 800,000 gallons of chemicals to disperse the oil on the surface and injected another 360,000 gallons under water to break it up near the seafloor, though the chemicals themselves may harm the environment. In 165 controlled fires, crews also burned an estimated 3.85 million gallons of oil on open water.
About one-third of federal waters in the Gulf remain closed to fishing.
"We are not really dealing with a monolithic spill," Coast Guard Adm. Thad Allen, the said national incident commander, said earlier this week, emphasizing the complexity of the spill. "We're dealing with about a 200-mile radius around the well site with thousands—maybe hundreds of thousands—of smaller patches of oil."
Write to Robert Lee Hotz at sciencejournal@wsj.com