What will happen to the Gulf oil?

NEW YORK (CNNMoney.com) -- There's a best-case scenario for what might ultimately happen to all the oil being spilled into the Gulf of Mexico, and it looks something like this:

Most of the oil doesn't reach shore, but it doesn't sink to the bottom of the ocean basin either. Rather, it gets dissolved in the microbe-rich first few hundred feet of water below the surface, where it it biodegrades within a period of weeks.

This is basically what BP and the government are trying to force by dousing the oil with chemical dispersants -- a risky maneuver. These toxic chemicals have never been used on this scale.

Of course, it could all go horribly wrong.

"This event is completely outside the box of prior experience," said Robert Carney, a professor of oceanography at Louisiana State University. "We really don't know what's going to happen."

What makes this spill so different is the depth and the chemicals. Because of high pressure and low temperatures, oil breaks down and disperses much differently if it's leaked at 5,000 feet than if it's leaked at 100. The heavy use of chemical dispersants, which BP is rumored to be flying in from stockpiles the world over, only adds to the uncertainty.

So far, BP's plan seems to be working. The slick has remained largely at sea -- though some oil has washed ashore on some Louisiana beaches and, possibly, the Florida Keys.

But what it's doing at sea is mysterious. Some of the oil is floating on the surface or breaking into so-called "tar balls" that look like oil pancakes several inches thick in diameter.

Reports over the weekend suggested that some of the oil had formed into plumes under the water, some up to 10 miles long, although Jane Lubchenco, head of the National Oceanic and Atmospheric Administration (NOAA), on Monday called those reports "misleading, premature and, in some cases, inaccurate."

Carney thinks that what's happening with the plumes is that the combination of pressure and chemicals is causing the oil to break into small particles, like a fog.

This fog is not thick enough to rise to the surface, but not heavy enough to sink. So it is remaining suspended in the ocean, maybe 600 to 1,000 feet below the surface.

These so-called plumes, said Carney, would not be a thick glob of crude oil -- they're more like cloudy water. In some cases the oil might not be visible to the naked eye.

But it would rob the water of oxygen and be harmful to marine organisms that came into contact with it.

Fortunately, most marine life does not inhabit those depths. The creatures preferring to stay closer to the surface or in shallower waters where there's light and, consequentially, more food.

The real danger comes if the oil either moves closer to shore or sinks deeper.

In deep water, the lack of oxygen and cold temperatures means the oil will take years to break down -- perhaps even centuries, said Lisa Suatoni, a senior scientist at the Natural Resources Defense Council's ocean program.

But that would be preferable to another possibility: Having the oil reach shore despite the mass amounts of dispersants used.

"Never, ever, ever let oil into salt marshes," Suatoni said, noting that it will soak into the soil and leech out again every time it rains. "It will be there for decades."

Suatoni was cautiously supportive of the plan to disperse the oil so far, although she notes that very little research has been done on what effects the dispersants themselves will have on the environment.

Even NOAA's Lubchenco acknowledges that dispersants aren't a silver bullet. "They are used to move us towards the lesser of two environmental outcomes," she said in a prepared statement.

Attempts to disperse the oil into the water column will invariably lead to wildlife deaths, as the dispersants are known toxins. But Suatoni said animal kills are generally preferable to the loss of habitat, which affects species for generations.

Either way, the different scenarios for what may happen to the oil underscore a basic fact of oil spills.

"Once the oil is out, it's out," said Suatoni. "There are no good outcomes, only different outcomes."