One year after the BP spill: Where's the oil?

Oil Spill 1 Year Later
Oil washes ashore with the waves onto New Harbor Island, La., May 6, 2010.

For months, Americans watched a disaster unfold. Underwater cameras captured oil gushing into the Gulf of Mexico after BP's well blew out one year ago Wednesday.

At first, the public had no idea how bad the leak was. The initial estimate was about 42,000 gallons a day. But one month later, the government put the leak at nearly 800,000 gallons a day. By mid-June, the estimate was more than 2-and-a-half million gallons.

We now know that over 86 days, about 207 million gallons leaked from the well. The question is - what became of it all? CBS News correspondent Mark Strassmann went back to the Gulf for answers.

GRAND ISLE, La. - If you know where to look, twilight's the best time to find oil in Plaqumines Parish, La.

Louisiana State University researcher Ben Dubansky , from the lab of Fernando Galvez at the Department of Biological Sciences, uses an ultra-violet light to show the oil. "All this is weathered oil," he says.

Disaster in the Gulf: One Year Later

On Baritaria Bay's northern tip, the dried oil was everywhere - clumped in soft marshland. Dubansky says, "I could take you to 100 sites like this."

Hoping to shame BP into continuing its cleanup, on Tuesday Louisiana officials spotlighted more oil.

Oil Slideshow: 100 days, 100 pictures

Last summer, the images of oil were everywhere - the threat was easy to spot. Last June, on our way back to shore, 10 miles into the Gulf, we found a vast floating field of black crude, thick like cake mix, rising and falling with the tide. I scooped out some of it with a fishing net. The oil was so heavy, even with both arms; I had a hard time lifting it.

(Scroll down to watch Strassmann's report from last year.)

But now what's left of the spill is harder to find. And scientists strongly disagree about the lasting impact of the spill.

Of that roughly 200 million gallon river of oil, government scientists estimate that 29 percent of it dispersed, 25 percent of it was recovered or burned off, 23 percent of it evaporated or dissolved. That leaves 23 percent - roughly 46 million gallons - that reached shore or stayed in the water.

Oil spill: looking back on 100 days of crude

Ed Overton, an environmental scientist at LSU says, "I don't think we're going to see any massive impacts as we go forward."

He believes the Gulf is recovering faster than expected, from its wildlife to its complex eco-system. Sun-baked oil left on land will degrade in the next few years, he says. But in deep waters, any remaining oil has fallen below detectable levels.

"All we're doing now, is postulating and making an educated guess," Overton says. "Of course it's still a guess."

But University of Georgia marine scientist Samantha Joye is much more pessimistic. Last December, Joye led a deep-dive expedition near the runaway well. "It looks like a graveyard," she says. She's now studying 450 core samples - many of them thick sludge smothering the sea floor.

"The people that live on the Gulf Coast know that there is a problem," Joye says. "It's fallen off the radar and people aren't thinking about it because they've been told that everything's fine when most certainly isn't fine."

How bad is it? No one knows for sure because there's never been a spill this massive in an ecosystem so complex. However everyone agrees on one point: Spill anxiety will last for years to come.

Watch Strassmann's report from last June below

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    Mark Strassmann

    Mark Strassmann has been a CBS News correspondent since January 2001 and is based in the Atlanta bureau.