The WeatherBird II is not a pretty ship. A boxy, businesslike, 194-ton vessel, it prowls the waters off St Petersburg, Fla. where it competes for attention with the cruise ships and sport yachts and other glamour boats. But the WeatherBird II was the buzz of the Gulf on Friday, after its alarming findings about the extent of the BP oil spill that’s spreading invisibly below the surface.

The ship is the principal research vessel of the University of South Florida’s College of Marine science, and it set off into the Gulf last Saturday on an $850,000 expedition to begin measuring just what kind of damage the spill has already done to the marine environment and what it might portend for the future.

By some estimates, up to a quarter of a million bbl. of oil are floating on the surface of the Gulf with an untold amount hovering at various points in the deep. Typically, spilled oil behaves the way all oil does, which is to say that it rises on water.

But the 830,000 gal. of dispersants that have so far been sprayed throughout the Gulf and injected directly into the billowing wellhead have caused much of the oil to dissolve into beads that hover at mid-depths.

The WeatherBird II is not a pretty ship. A boxy, businesslike, 194-ton vessel, it prowls the waters off St Petersburg, Fla. where it competes for attention with the cruise ships and sport yachts and other glamour boats. But the WeatherBird II was the buzz of the Gulf on Friday, after its alarming findings about the extent of the BP oil spill that’s spreading invisibly below the surface.

The ship is the principal research vessel of the University of South Florida’s College of Marine science, and it set off into the Gulf last Saturday on an $850,000 expedition to begin measuring just what kind of damage the spill has already done to the marine environment and what it might portend for the future.

By some estimates, up to a quarter of a million bbl. of oil are floating on the surface of the Gulf with an untold amount hovering at various points in the deep. Typically, spilled oil behaves the way all oil does, which is to say that it rises on water.

But the 830,000 gal. of dispersants that have so far been sprayed throughout the Gulf and injected directly into the billowing wellhead have caused much of the oil to dissolve into beads that hover at mid-depths.

The WeatherBird II expedition, led by SFU chemical oceanographer David Hollander wanted specifically to explore the DeSoto Canyon, a deep erosional valley south of the Florida panhandle and about 20 miles (32 km) northeast of the Deepwater Horizon wreck site.

The DeSoto is to the Gulf what a rainforest is to a land-based ecosystem: a densely fertile area where life forms fairly explode. It’s the upwellings of nutrient-rich water that make the area so hospitable to fish, coral and other living things.

On the surface, the waters of the region look clean, but just below the surface and down to about 3,300 ft. (1 km), Hollander and his team found a six-mi. (9.6 km) wide, 22-mi. (35.4 km) long oil bloom, broken into millions of bits and beads and moving with the current. It had not reached the canyon yet, but it was heading that way.

The dispersants responsible for the condition of the oil are made up of a stew of chemicals, about one-third of which are proprietary — which means that even BP does not know exactly what it’s spraying.

But it’s the surfactants — a lipoprotein used in soaps that reduces the surface tension of liquids — that are the most active ingredient, reducing the surface tension of a liquid and breaking the oil from a slick into droplets.

The finer the breakdown is, the easier it becomes for both big creatures like bluefin tuna or swordfish and tiny creatures like krill or shrimp to ingest the oil and the surfactants themselves.

"It’s not at the surface so it doesn’t look so bad,” Kevin Kleinow, professor of veternary medicine at Louisiana State University told the Associated Press, "but you have a situation where it’s more available to fish.”

So far, it’s impossible to predict exactly where the toxic cloud is heading. If shallow currents take hold of it, they could keep the chemicals near the surface, hastening the breakdown that occurs when they’re exposed to sunlight.

But if the chemicals hitch a ride on deeper currents, they could sweep down into the canyon, turn south along the west coast of Florida, and then reach the Keys.

It’s not even out of the question for them to catch the Loop Current and swing up the Atlantic coast of the U.S. The effect on ocean life could be devastating and it will by no means be limited to the fish themselves

"There are two elements to it,” Hollander told the AP. "The plume reaching waters on the continental shelf could have a toxic effect on fish larvae, and we may also see a long-term response as it cascades up the food web.”

The new plume is actually the second such aquatic cloud discovered. The first, however, was flowing toward deep water when last mapped and is not seen as anywhere near the threat the new one is.

Worse, as the oil continues to pour from the well and dispersants continue to be sprayed on the surface, no one can say how many more toxic blooms are out there already — or how many have yet to form.

TIME