The sight of an oil slick spreading across the surface of the Gulf of Mexico is bad enough. But now scientists from the University of South Florida have found signs that a 6-mile-wide plume of invisible oil is snaking beneath the surface, in the deepest recesses of the gulf.
The thickest concentration, they found, was more than 2 miles beneath the surface — a mile deeper than where the Deepwater Horizon well has been spewing oil for the past month — and about 20 miles northeast of the collapsed rig.
The plume of dissolved oil stretched 6 miles down, said David Hollander, a USF chemical oceanographer and lead investigator for the project. This is the second oil plume to be discovered by scientists, and it marks the first time such plumes have been detected after a spill, Hollander said. He compared them to streams of lava flowing out of an undersea volcano.
While the fudgelike goo coating Louisiana's marshes is getting lots of television coverage, the two undersea plumes show damage is also occurring where no one can see it: deep in the gulf, miles from land, where marine life has always been abundant and yet largely unobserved.
The USF research vessel Weatherbird II was dispatched Saturday to take samples in the DeSoto Canyon, a deep valley that cuts through the continental shelf south of the Florida Panhandle. In the canyon, an upwelling of nutrient-rich water means far more fish and other species swim there.
The scientists' big concern, Hollander said, is whether the oil they found is concentrated enough to be toxic to marine life. It could affect the whole food chain, he said.
The canyon area is a popular destination for local fishing boats, said Bob Spaeth, owner of Madeira Beach Seafood, the area's largest seafood house and home dock for many longline boats, because "it is pristine. It has great habitat.''
The fishermen are willing to make the day-and-a-half journey because they know they will catch bluefin tuna, swordfish, king mackerel and grouper, Spaeth said. If toxic levels of oil have contaminated the fish there, Spaeth said, "that's a disaster.''
The fish are not the only potential deep-sea victims of the spill. It could affect everything from the 10-foot-long giant tube worms rooted to the floor of the gulf to the sea turtles, sharks, whales and dolphins that spend their lives far from shore, say the experts.
"I would be worried about every marine species that swam through that plume," said John Williams, executive director of the Southern Shrimp Alliance, based in Tarpon Springs.
Currently federal officials have closed about 22 percent of the gulf to both commercial and recreational fishing. USF College of Marine Sciences Dean William Hogarth promised that if the area where the plume was found wasn't already covered by that ban, it will be by today.
A big question is where the plume will go next. It could continue spreading until it gets onto the continental shelf and is pushed close to shore. Another USF oceanographer, Robert Weisberg, warned congressional representatives this week that if subsurface oil gets lifted onto the shelf it could reach west Florida's wetlands and beaches, which he called "a very serious concern."
There is no ongoing government monitoring program for what's going on in the gulf, Weisberg said. The USF voyage cost $850,000 — funded by the state — and at this point there is no money for a follow-up trip.
The USF ship, scheduled to return today, went out after scientists from several universities working aboard the research vessel Pelican told the New York Times of finding plumes of oil 3 miles wide and 10 miles long beneath the gulf's surface. That plume was spreading southwest of the rig.
Computer models run by Weisberg had predicted the location of the southwestern plume found by the Pelican, Hollander said. Weisberg's model also suggested there could be a similar plume headed northeast, he said, so that's where the USF ship went.
The scientists aboard the ship — some from USF, some from the Florida Fish and Wildlife Research Institute in St. Petersburg — discovered the plume on Tuesday. What's not known is the role that chemical dispersants play in the plume. BP has been spraying the dispersants both on the surface slick and directly on the gushing wellhead in the deep ocean, something never before attempted. The dispersants, being used in unprecedented quantities, are supposed to spread the oil so it will evaporate and degrade more quickly. That could be what has created the plumes, Hollander said.
The concern is that the dispersants are simply holding the oil below the surface, where it is harder to clean. So far, tests by the U.S. Environmental Protection Agency have found no signs that the dispersants are harmful to sea life, but the EPA has ordered BP to look for a less toxic version.
Once the Weatherbird II returns to port, scientists will conduct further tests to determine whether the plume is made of weathered oil droplets or oil linked to dispersants, Hollander said.
The one piece of good news: Tests conducted by the Weatherbird II between the loop current and the Florida coast showed clean water, no weathered oil on the surface and no sign of oil beneath the waves. But that doesn't mean it will stay that way.
Rowan Gould, acting director of the U.S. Fish and Wildlife Service, has predicted the spill "will affect fish and wildlife resources … for years to come, if not decades."
Times staff writers Stephen Nohlgren and Alex Leary contributed to this report.