Gulf oil spill: An ‘ecological disaster’?

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The enormous oil slick could compound Louisiana’s perennial problem with a low-oxygen “dead zone� that spreads across the seafloor over an area the size of New Jersey, killing fish and shellfish that cannot swim or scuttle away.

“Everybody is really worried about potential ecological disasters,� said Nancy Rabalais, executive director of the Louisiana Universities Marine Consortium in Cocodrie, La., and a top researcher in the field. “The oil is going to move somewhere. It’s not as likely to move offshore.�

Louisiana’s dead zone, the world’s second largest (after the Baltic Sea), arrives every year after fertilizer washing down the Mississippi River feds enormous blooms of algae that die, sink to the bottom and begin to decay. The decomposition sucks oxygen out of the seawater, leaving little or none for fish and other marine life.

Monitoring stations run by the marine consortium have already detected some low-oxygen zones, said Rabalais, from her office on Terrebonne Bay, adding that the year’s zone could be exacerbated by surface oil blocking lifegiving oxygen from enriching the water. “The oil sheen, the layering on the surface of the water, could prevent the diffusion of oxygen into the water,’ she said. ‘It could aggravate the low-oxygen zone that we’re already seeing develop in the gulf.�

For Rabalais, the oil creeping toward the Louisiana coastline dredges up dark memories of when
she was a young research assistant studying bottom-dwelling sea life in the offshore oil fields. She was living in Port Aransas, Texas, when the 1979 blowout of Mexico’s exploratory oil well, named Ixtoc, sent
waves of crude to gum up the U.S. Gulf Coast.

“It put a noxious gooey oil on the beaches, got into every crack and crevice and penetrated the animal burrows, killing mud shrimp and everything else,� said Rabalais. “It’s probably still there. It takes oil
a long time to weather and degrade, especially when it gets into the rocks and jetties.� For now, she said, coastal residents are watching for signs of an arriving slick.

“Everybody is really worried about potential ecological disasters,� said Rabalais. “The oil is going to move somewhere. It’s not as likely to move offshore.�

Researchers continue to find hidden, toxic pools of oil left over from the 1989 Exxon Valdez tanker spill off Alaska’s coastline, killing pink salmon eggs and retarding the population growth of sea otters, harlequin ducks and other wildlife. Although oil does decompose, studies show that oily pockets tucked beneath boulders or buried below gravel and mussel beds in Prince William Sound escape sunlight, oxygen and waves that would break them down. The area of rich sea life around the infamous tanker spill is one of the best studied in the world thanks to the flow of research dollars from Exxon and the federal
government.

Related:
Photos: Oil spill spreads in the Gulf of Mexico
Efforts to fight Gulf of Mexico oil spill are ramped up
Interactive: Burning spilled oil

-- Ken Weiss