Researchers confirm oil toxic to sea life

08/17/10 Kate Bradshaw
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A double-dose of bad news about oil in the Gulf: Last night, USF researchers returned from a fact-finding mission with evidence of toxic oil on the ocean floor. This comes within 24 hours of a team of Georgia scientists’ finding that, despite what the government says, most of the oil is still out there.

A National Incident Command study asserts just 25% of the BP oil is still lingering out in the gulf. But University of Georgia marine science Professor Samantha Joye said the problem with the study is that it assumes that “dispersed” means “gone.”

“If you use conservative numbers on what we know on how oils biodegrade, how fast things turn over, then you’ve come up with 70-80% of the oil still out there.”

In late May, it was discovered that much of the dispersed oil had formed massive subsurface plumes. Joye’s team had studied one plume southwest of the blowout site, while University of South Florida’s spill research team studied two northeast of the broken well. Joye said she didn’t want to speculate on the current size of the oil plumes out in the gulf.

“I don’t even think it’s fair. When we were out there, I know how big the feature was, when we were there. It’s almost certainly not the same feature, now. It’s changed. It’s certainly changed since then. So, to speculate on the size would just be absolute and utter speculation, and I don’t want to go there.”

She said the plumes are isolated, so it’s not like the entire gulf is inundated with broken-down crude. Still, Joye said, what’s there poses two major problems for the gulf ecosystem. One is oxygen depletion, which can lead to dead zones.

“The bottom line is that as long as there’s oil floating around in the water, which there undoubtedly is oil floating around in the water, that oil and gas represent a potential oxygen sink for the water columns. We have to keep evaluating this system. We have to keep making measurements of both oil and gas concentrations and oxygen respiration rates, and break down rates of the complex mixture, to see how the system’s changing over time.”

She said the areas of low oxygen are not yet technically dead zones, but such a steep increase of hydrocarbon concentrations is a concern because of potential toxicity to sea life. Joye said this is especially true close to the blowout site.

“The concentrations of oil in the water were probably only toxic to organisms within a small sphere around the well-head. Maybe 5k or 10k, 5k is a fair guess. Once you get beyond that, the concentrations are fairly dilute.”

Today, another group of scientists confirmed fears that oil may be toxic to the food chain. Just back from a 10-day research mission in the gulf, a team of University of South Florida researchers says they’ve found dispersed oil settled on the sea floor 40 miles south of Panama City. USF marine science Professor David Hallander led the mission. He said there’s evidence that oil accumulated on the ocean floor is toxic to the microscopic phytoplankton that forms the base of the gulf food web.

“The idea that this could have an impact on the food web and on the biological system is certainly a reality. This is not addressing the question of turtles, or of sharks, or of birds which are at the top of food web, but rather the organisms at the base of the food web.”

He said animals higher in the food chain will probably see indirect effects of this.

“You’re not picking off upper trophic levels like turtles, or pelicans, or sharks, or dolphins, which is at the top of the pyramid. You’re actually attacking some of the foundations of the pyramid. That’s where there’s concern. What happens in the long term?”

Another problem is the location of the oil. It sits at the bottom of De Soto Canyon, which Hallander said is an underwater conduit between the blown-out well and a narrow part of the continental shelf.

“Right now, there’s an interesting climatological condition, which ends up causing upwelling, where you’re bringing deeper waters up onto the continental shelf and upwelling onto the beaches. So, this is a mechanism in which you can actually train water to come up from the deeper edges of the continental margin, and the De Soto Canyon is a very broad, easy access. Also, what’s a bit troubling is that this is a direct contour to the location of the Deepwater Horizon well.”

Over the next two weeks, the team will further analyze their data. This includes looking for dispersants and confirming that the oil they’ve found is indeed from BP’s blown-out well.

Florida Public Radio's Steve Newborn contributed to this report.

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