The work of patrolling Florida's waters for oil begins in the skies. Three times a day, crews take off from the Coast Guard station in Clearwater to search for oil.

This C-130 will cover 2,400 kilometers, focusing on waters near Pensacola. Lieutenant Commander Scott Murphy leads the crew.

"This is the first day we've been out here and we've had blue skies and 10-15 miles [24 km] of visibility," said Lieutenant Commander Murphy. "Other than that it was driving rain the first day."

Crews visually scan for ribbons and sheets of oil. They also use radar to help spot oil just below the water's surface.

Officials compare the observations from Coast Guard flights to data from satellites or surface vessels. The results produce a map of the oil spill and its path.

"That's got to be it," said co-pilot Brian Boland. "See the big circle patches?"

About 50 kilometers off the coast of Pensacola, crews spot something in the water.

The challenge is to pick out oil from other dark spots, such as shadows made by clouds or patches of seaweed.

"When you are going three miles [five kilometers] a minute, it can be hard to clearly define that," said Murphy. "So typically we report those positions, tell them what we see, that it could possibly be seaweed, and they can vector [send] a surface asset [vessel] to confirm."

Back on the ground, the observations are sent to a task force tracking the spill. It's difficult to keep track of the slick, says co-pilot Brian Boland.

"We flew on it for a couple hours, and now it's 24 hours before we go fly again," he said. "And there is no way to know if the current or the wind or the waves or what is going to affect it. If it is going to grow, or push toward shore or come off shore."

Oil has already come ashore at Pensacola Beach. Clean-up crews worked over the July 4th holiday weekend, usually a time when tourists go to the beach. Experts say cleaning a beach is relatively easy.

The job would be tougher in fragile wetlands, like in Key Largo. Wildlife officials routinely patrol these shallows waters, a habitat for many fish and shellfish.

Experts fear the oil could destroy vegetation and endanger the entire food chain. National park ranger Dan Kiger says oil poses a special risk to mangroves and sea grass, for example.

"The sea grass is very important," said Dan Kiger. "It filters the water, it keeps the water clean. Manatees eat the sea grass, turtles eat the sea grass. It acts as sanctuary for the small juvenile fish."

So far, no oil from the Deepwater Horizon leak has been found near the Florida Keys. Experts say the risk is low, in part because weather systems have kept the oil away.

John Hunt is with the Florida Wildlife Conservation Commission. He says the Keys have been lucky, so far.

"I hate to use the work lucky in terms of an oil spill, because someone else is having a lot of issues and we know where the environment is having issues," said John Hunt. "But from a South Florida perspective, even the location of where it happened, we had a bit of luck."

While clean-up continues in Louisiana, Alabama and Mississippi, officials in Florida are watching to guard against oil damage here as well.

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（来源：VOA 编辑：陈丹妮）