Deepwater Mystery: Oil Loose In The Gulf
Streaming video of oil pouring from the seafloor and images of dead, crude-soaked birds serve as visual bookends to the natural calamity unfolding in the Gulf of Mexico.

But independent scientists and government officials say another disaster is playing out in slow motion - and out of public view - in the mysterious depths between the gusher and the coast, a world inhabited by sperm whales, gigantic jellyfish and diminutive plankton.

More than a month after the BP PLC spill began, the disaster's dimensions have come into sharper focus with government estimates that more than 18 million gallons of oil - and possibly 39 million gallons - has already poured from the leaking well, eclipsing the 11 million gallons released during the Exxon Valdez spill.

"Every fish and invertebrate contacting the oil is probably dying. I have no doubt about that," said Prosanta Chakrabarty, a

Louisiana State University fish biologist.

The deep Gulf is an area where light can't penetrate and researchers rarely venture.

Yet what happens there can ripple across the food chain. Every night the denizens of the deep make forays to shallower depths to eat - and be eaten by - other fish, according to marine scientists who describe it as the largest migration on earth.

In turn, several species closest to the surface - including red snapper, shrimp and menhaden - help drive the Gulf Coast fishing industry. Others such as marlin, cobia and yellowfin tuna sit atop the food chain and are chased by the Gulf's charter fishing fleet.

Many of those species are now in their annual spawning seasons. Eggs exposed to oil would quickly perish. Those that survived to hatch could starve if the plankton at the base of the food chain suffer. Larger fish are more resilient, but not immune to the toxic effects of oil.

The Gulf's largest spill was in 1979, when the Ixtoc I platform off Mexico's Yucatan peninsula blew up and released 140 million gallons of oil. But that was in relatively shallow waters - about 160 feet deep - and much of the oil stayed on the surface where it broke down and became less toxic by the time it reached the Texas coast.

Since BP's Deepwater Horizon exploded and sank more than five weeks ago, scientists said they have found at least two sprawling underwater plumes of what appears to be oil, each hundreds of feet deep and stretching for miles.

A plume reported last week by a team from the University of South Florida, was headed toward the continental shelf off the

Alabama coastline, waters thick with fish and other marine life.

On Sunday, BP's CEO Tony Hayward disputed the existence of the plumes, saying testing by the company showed no evidence that oil was being suspended in large masses underwater. Hayward said oil's natural tendency is to rise to the surface, and any oil found underwater was in the process of working its way up.

However, the researchers said oil in the plumes had dissolved into the water, possibly a result of chemical dispersants used to break up the spill. That makes it more dangerous to fish larvae and creatures that are filter feeders.

Responding to Hayward's assertion, one researcher noted that scientists from several different universities have come to similar conclusions about the plumes after doing separate testing.

No major fish kills have yet been reported, but federal officials said the impacts could take years to unfold.

"This is just a giant experiment going on and we're trying to understand scientifically what this means," said Roger Helm, a senior official with the U.S. Fish and Wildlife Service.

In 2009, LSU's Chakrabarty discovered two new species of bottom-dwelling pancake batfish about 30 miles off the Louisiana coastline - right in line with the pathway of the spill caused when the Deepwater Horizon burned and sank April 24.