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What if there was an oil spill off Tampa Bay?

A week before the Deepwater Horizon rig exploded 50 miles off the coast of Louisiana, a powerful U.S. senator vowed to allow rigs to drill 45 miles of Florida's coast.

Sen. Byron Dorgan, D-S.D., said he preferred that distance to President Barack Obama's proposed 125-mile limit because "you get more energy out of that and you still have the proper safeguards for a visual line of sight and so on."

As Deepwater Horizon has shown, though, there are bigger problems with offshore drilling than just keeping rigs out of sight of the tourists on the beach.

Oil continued gushing from a mile beneath the surface of the Gulf of Mexico last week — perhaps far faster than earlier estimates said — and tar balls washed ashore as far east as Alabama. So far no oil has reached Florida, but officials say that unless the leaks are shut off, it's only a matter of time — and the damage could take decades to fix.

So as an experiment, the Times wanted to see what areas would be most affected if a spill like Deepwater Horizon occurred 50 miles off the Tampa Bay region's coastline, where the environment and the economy are, as they are in most of Florida, inextricably linked.

There are some similarities between the Florida and Louisiana coasts. Both are thick with marshes and mangrove forests that are important for the growth and development of a wide variety of species, including shrimp and oysters. They would be nearly impossible to clean should oil get into them.

Unlike Louisiana, Florida has white sandy beaches. Although oil is easier to clean off a beach than off a marsh, in previous spills, such as the Ixtoc spill of 1979, it tended to persist for years in "oil reefs" off the Texas coast that broke loose after every storm and washed fresh tar balls onto the beach.

Worse, if an oil spill got into Tampa Bay, getting it out again would be difficult because the bay doesn't flush itself well. There is other bad news for the ecosystem.

Oil on the water's surface can shadow sea grass, preventing it from growing. If oil seeps into the roots, it could prevent them from ever regrowing.

Mangroves are highly susceptible to pollution. Oil can kill them within a few weeks, and recovery can take at least a decade and maybe even half a century. Mangroves are the center of their own delicate ecosystem that supports a vast variety of other living things. Look at the map on this page to locate concentrations of sea grass beds and other sensitive spots in our area.

Drilling 50 miles off Louisiana requires sinking a well 5,000 feet deep. Fifty miles off Florida's coast, the water isn't nearly as deep. That means any spill would reach Florida's shoreline much more quickly, said University of South Florida oceanographer Robert Weisberg. However, notes USF oceanographer Al C. Hine, because of the difference in the geology between Florida and Louisiana, a blowout off Florida would not have occurred in the same way as the Deepwater Horizon explosion.

One thing we could not depict on this map: how the daily sea breeze would bring the possibly toxic fumes from the spilled oil onshore.

"Every morning when the sun comes up, it heats the ground all across Florida," explained retired Florida State University oceanographer Wilton "Tony" Sturges. "This nice warm air rises, bringing an onshore breeze that people like so much … But if there is something just offshore that you wish would go away, you're in trouble."

What if there was an oil spill off Tampa Bay? 05/17/10 [Last modified: Monday, May 17, 2010 3:46pm]

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