Naked Science Forum
Life Sciences => The Environment => Topic started by: paul.fr on 24/03/2009 17:51:57
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Two decades after the worst oil spill in U.S. history, huge quantities of oil still coat Alaska's shores with a toxic glaze, experts say.
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More than 21,000 gallons of crude oil remain of the 11 million gallons of crude oil that bled from the stranded tanker Exxon Valdez on the night of March 23, 1989.
The oil—which has been detected as far as 450 miles (724 kilometers) away from the spill site in Prince William Sound—continues to harm wildlife and the livelihoods of local people, according to conservation groups. (See an Alaska map.)
Dennis Takahashi-Kelso, who was on the ground at the Exxon Valdez disaster as Alaska's commissioner of environmental conservation, remembers wading through knee-deep pools of bubbling, thick oil. The smell of the pure oil was intense and pungent, he said.
When he returned to the same beaches years later, he found "surprisingly fresh" oil just below the sand.
(Related: "Alaska Oil Spill Fuels Concerns Over Arctic Wildlife, Future Drilling".)
"The damage that [the spill] created is something beyond anyone's imagination," said Michel Boufadel, Temple University's Civil and Environmental Engineering chair, who has just completed research on why the oil persists.
Oil-Munching Bacteria
An 11,000-person crew removed oil from the beaches until 1994, when government officials decided to end the clean up effort. At that time, what was left of the the oil was naturally disintegrating at a high rate, and experts predicted it would be gone within a few years. But they were wrong.
Oil naturally "disappears" through two processes: As the tide rises over an oil patch, the water sloughs off bits of oil, which then disperse into the ocean as tiny, less harmful droplets that can biodegrade easily.
Biodegradation occurs when bacteria or other microorganisms break down oil as part of their life cycle.
But Prince William Sound is what ecologists call a closed system—it's not exposed to big, pounding waves, so the oil has time to seep into the sand, according to Margaret Williams, who oversees conservation in the Bering Sea for the nonprofit World Wildlife Fund (WWF).
In these stagnant areas, oil-munching bacteria don't receive the nutrient-rich water flow they need to thrive, said Temple University's Boufadel.
"The assumption that oil is going to disappear is surprising—we have to put an effort into understanding oil spills and how they interact with the environment much better," Boufadel said.
Boufadel's research on the leftover oil was funded by the Exxon Valdez Oil Spill Trustee Council, a state and federal partnership to restore the damaged ecosystem.
Shangri-La of the North
Twenty years of oil exposure has injured this stretch of Alaska's coast, which WWF's Williams calls the Shangri-la of the north.
In its first toxic sweep, the oil spill killed about 250,000 seabirds, 4,000 sea otters, 250 bald eagles, and more than 20 orca whales, according to WWF.
Today, one of the orca pods that lost family members has not recovered.
Sea otters and harlequin ducks continue to die by digging into the sand for food and releasing buried oil.
At the bottom of the food chain, pink salmon eggs and small invertebrates such as mussels and clams are not yet back to their original population levels.
And local fishers, who lost more than U.S. $286 million after the herring fishery collapsed in 1989, are still waiting for the fishery to rebound.
Stake in the Heart
Solutions exist to clean up the oil, Temple University's Boufadel said: For instance, increasing water flow to the most isolated patches could help the oil-hungry microbes do their job.
But the focus now should be on how to prevent spills in the future, said Takahashi-Kelso, now executive vice president at the Ocean Conservancy.
"Twenty years out, the real value of what we've learned is what decisions we make and how wise we are in managing risk," he said.
For instance, the disaster inspired the 1990 Oil Pollution Act, which, among other measures, requires that by 2020 all oil tankers like the Exxon Valdez have double hulls—a layer of protection that may prevent oil spills.
But the U.S. government's recent plan to sell offshore oil-drilling leases is risky, especially when the region is already threatened by climate change, WWF's Williams said. (See how climate change is changing the Arctic.)
For instance, oil drilling could hurt Bristol Bay, "the little engine" of the Bering Sea that produces up to half of the United States' wild seafood, Williams said.
"To add new carbon dioxide emissions by developing petroleum resources," she said, "is driving another stake in the heart of America's Arctic."
http://news.nationalgeographic.com/news/2009/03/090323-exxon-anniversary.html?source=rss