The Gulf of Mexico will recover from the oil leak, but it may take decades.


SHORELINES HIT BY oil in the past offer clues to what people living along the Gulf Coast in the United States can expect. The picture is not hopeless, although damage is likely be persistent.

“Thoughts that this is going to kill the Gulf of Mexico are just wild overreactions,” said Jeffrey W. Short, a scientist who led some of the most important research after the Exxon Valdez spill and now works for an environmental advocacy group called Oceana. “It’s going to go away, the oil is. It’s not going to last forever.”

But how long will it last?

Only 20 years ago, the conventional wisdom was that oil spills did almost all their damage in the first weeks, as fresh oil loaded with toxic substances hit wildlife and marsh grasses, washed onto beaches and killed fish and turtles in the deep sea.

But disasters like the Valdez in 1989, the Ixtoc 1 in Mexico in 1979, the Amoco Cadiz in France in 1978 and two Cape Cod spills, including the Bouchard 65 barge in 1974 - all studied over decades with the improved techniques of modern chemistry and biology - have allowed scientists to paint a more complex portrait of what happens after a spill.

It is still clear that the bulk of the damage happens quickly, and that nature then begins to recuperate. After a few years, a casual observer visiting a hard-hit location might see nothing amiss. Birds and fish are likely to have rebounded, and the oil will seem to be gone.

But often, as Dr. Short and his team found in Alaska a dozen years after the Exxon Valdez spill, some of it has merely gone underground, hiding in pockets where it can still do low-level damage to wildlife over many years. And the human response to a spill can mitigate - or intensify - its long-term effects. Oddly enough, some of the worst damage to occur from spills in recent decades has come from people trying too hard to clean them up.


DAVID ROCHKIND FOR THE NEW YORK TIMES/ ABOVE RIGHT, KATHERINE TAYLOR FOR THE NEW YORK TIMES


Long after an oil spill is no longer visible, toxic traces remain. At left, scientists search for residue of the 1979 Ixtoc 1 spill in the Gulf of Mexico. Above, marsh grass in Cape Cod is healthy where untouched by a 1974 spill, and stunted where suffused. Top, a floating boom to fend off oil is placed in a channel in Port Mansfield, Texas, in 1979.


Past Spills Offer Clues to Gulf’s Future Health


It is hard for scientists to offer predictions about the present spill, for two reasons.

The ecology of the Gulf of Mexico is specially adapted to break down oil, more so than any other body of water in the world - though how rapidly and completely it can break down an amount this size is essentially unknown.

And because this spill is emerging a kilometer and a half under the surface and many of the toxic components of the oil are dissolving into deep water and spreading far and wide, scientists simply do not know what the effects in the deep ocean are likely to be.

Still, many aspects of the spill resemble spills past, and that gives researchers some confidence in predicting how events will unfold.

Remarkable Persistence

In 1969, a barge hit the rocks off the coast of West Falmouth, Massachusetts, spilling 716,000 liters of fuel oil into Buzzards Bay. Today, the fiddler crabs at nearby Wild Harbor still act drunk, moving erratically, reacting slowly to predators, and perhaps not adequately playing their crucial role in tilling the salt marsh, which helps provide oxygen to the roots of salt marsh grasses.

The odd behavior is consistent with a growing body of research showing how oil spills of many types have remarkably persistent effects, often at levels low enough to escape routine notice.

In Alaska, the Exxon Valdez spill ultimately oiled 1,930 kilometers of shoreline. By the late 1990s, the oil seemed to be largely gone, but liver tests on ducks and sea otters showed that they were still being exposed to hydrocarbons, chemical compounds contained in crude.

Dr. Short, then working for the National Oceanic and Atmospheric Administration, mounted a series of excavations to figure out what had happened, with his team ultimately digging thousands of holes in Alaska’s beaches. Oil was found in about 8 percent of them, usually in places with too little oxygen for microbes to break it down. At the rate the oil is breaking down, Dr. Short estimates that some of it could still be there a century from now.

Perhaps the greatest single hazard from the Deepwater Horizon disaster in the gulf is the long-term erosion of delicate coastal wetlands it could cause. At another spill site on the Massachusetts coast, not far from the West Falmouth spill, the legacy of oil contamination is evident in the difference between two marshes on either side of a pebbly shoreline road.

On one side, where the marshes were suffused in 1974 when the grounded Bouchard 65 barge dumped 42,000 to 140,000 liters of fuel oil into the sea, the grasses are stunted and sparse. They cling tentatively to the edge of the sandy beach. But the grasses on the other side, untouched by oil, rise tall and thick.

Louisiana’s coastline contains some of the most productive marshes in the world, delivering an abundance of shrimp and oysters and providing critical habitat and breeding ground for birds and fish.

Bad Choices in France

Oil spills produce a powerful impulse to clean up the oil . But that impulse can itself be a source of destruction.

No case illustrates that point more starkly than the 1978 spill of the Amoco Cadiz tanker. Caught in a gale, it was propelled against rocks near the shore of northwestern France, spilling 254 million liters of crude oil that washed over 300 kilometers of the coast of Brittany.

The immediate damage was bad enough: at least 20,000 seabirds found dead, thousands of tons of oysters lost and fish ridden with ulcers and tumors. But then the French authorities made it worse.

Using bulldozers and tractors, they scraped close to 50 centimeters of oiled sediment from the top in the most polluted marshes and also straightened and deepened some natural tidal channels, to improve flushing.

Over time, these proved to have been disastrous judgments.

In areas that were not bulldozed, nature ultimately broke down most of the oil and the vegetation came back. The bulldozed marshes are still missing as much as 40 percent of their vegetation.

Much the same dynamic played out in Alaska after the Exxon Valdez spill. In some areas, Exxon power-washed oiled beaches with high-pressure, hotwater sprayers. Scientists ultimately determined that it was a disaster for the tidal ecology, with clams and other organisms showing greatly delayed recovery on the laundered beaches .

The lesson, scientists say, is not that people should never try to clean up an oil spill. But the calculation of how much to do is tricky .

In Louisiana, battles have erupted between the Army Corps of Engineers and local residents, led by Governor Bobby Jindal, over proposals to build sand and rock barriers to block the oil from coming into the marshes. The corps has been cautious on approval permits , warning that changed waterflow patterns could hurt marsh ecology.

No matter how that battle plays out, a tough and potentially contentious issue in Louisiana in coming months may be the question of whether the marshes should be burned.

If the top layer of grasses and the clinging oil are burned off, the roots should survive and allow healthier grasses to sprout back. But scientists say that can be done only if there is no chance of new oil coming in, since burning might expose the roots buried in the sediment, making them vulnerable to absorbing the oil.

Natural Resilience

The Ixtoc blowout of 1979-80 is the closest analogy to the BP spill . Ixtoc soiled hundreds of kilometers of Gulf of Mexico beaches, all the way to Texas.

“As a young scientist, I thought, ‘Oh, no, this is wiping out our beaches,’ ” said Wes Tunnell, a researcher at the Harte Research Institute for Gulf of Mexico Studies in Texas.

But then he watched in amazement as the recuperative powers of the gulf kicked in.

Because oil constantly seeps into the gulf from natural fissures, the water is teeming with microbes adapted to break oil down . The warm water speeds up this process and also helps some species recover faster .

No one can be sure that the recovery from the BP spill will be a replay of Ixtoc.

“Thirty years ago, that 140 million gallons of oil went somewhere,” Dr. Tunnell said. “The gulf recovered and became very productive again. My concern is: Is it as resilient today as it was 30 years ago?”


In Sea Temperature, a Glimpse of Hope

The gulf’s warmer waters may contribute to the natural recovery of the ecosystem.

Oil-eating microbes will break oil down faster in the warmer waters of the Gulf of Mexico ...
Source: NOAA


... than in the colder waters of the Gulf of Alaska, which were polluted by the Exxon Valdez spill in 1989.