Extent Of Damage Under Ocean's Surface Unknown
GUY RAZ, host:
Joining us for more on the spill and its potential impact is Jim Cowan. He is a professor of oceanography and coastal sciences at Louisiana State University.
Jim Cowan, welcome to the program.
Dr. JAMES COWAN (Professor, Department of Oceanography and Coastal Sciences, Louisiana State University): Thank you.
RAZ: Describe what happens to oil on its journey as it sort of begins to rise to the top of the ocean.
Dr. COWAN: Well, first of all, when it's (unintelligible) pressure, obviously it's compressed, and so it's a little bit more dense. So it floats relatively slowly at first. And then as it rises in the water column, it expands and actually begins to rise to the surface more quickly. But even though we're about 1,000-foot journey, it does have a lot of time to start weathering and breaking down. That mostly occurs when it reaches the surface.
RAZ: What do you think it looks like deep inside the ocean where the leak has spread?
Dr. COWAN: Well, what I suspect is happening is that a relatively small fraction of the oil is actually reaching the surface mainly because of the decision, which I think is a misguided one to use dispersants at the wellhead.
You know, I understand that most of the focus has been on the coast, but the fact that the dispersants are being used at the wellhead means that the oil is breaking up; to some degree, it's emulsifying as it rises. And it's settling out at different layers in the sea. And some of the heavier fractions are probably staying on the seafloor. So, certainly, there's potential for it to impact not just the coast, but communities and fishes and invertebrates on the continental shelf.
RAZ: Could it literally strangle sea life below? I mean, (unintelligible) of...
Dr. COWAN: Yeah, I mean, particularly some of the things like soft corals and sponges that are actually - you know, sponges are filter feeders and corals have very small polyps, and the polyps can easily get smothered by the oil and die.
And one of the really important factors that we don't know very much about at all is the toxicity of the oil dispersant mixture. The dispersants are breakdown when they're at the surface and the toxicity of them is known relatively well. But the toxicity of those dispersants in combination with the oil is essentially unknown at depth.
RAZ: We do not know how...
Dr. COWAN: We do not know.
RAZ: We do not know how these dispersants might also damage ecosystems (unintelligible).
Dr. COWAN: Right. I mean, there are some preliminary evidence that the dispersants themselves may be more toxic than the oil at depth.
RAZ: I've read the sort of parts of the underwater ecosystem has been described as kind of standing forests of trees made up of coral. Can you describe what it looks like down there?
Dr. COWAN: What I would more describe it as a series of closely spaced flattop mountains that rise up from the seabed tens to hundreds of meters. And the sides and tops of these things are covered with a very, very diverse community of sponges and sea fans and soft corals and some hard corals. And so, it essentially doesn't look dissimilar from a normal coral reef, except that the features themselves are geologic rather than are built by the animals. But if you can picture what a coral reef looks like in your mind, then you can kind of get a sense of what these shelf-edge banks look like.
RAZ: It's hard for many of us to kind of imagine and to sort of get a sense of how huge this catastrophe is. Obviously, in 1989 with the Exxon Valdez, we could see seagulls, we could see animals on the coast covered in oil. We know that some clam and mussel beds are still contaminated in Prince William Sound in Alaska. What do we know about the lasting impact of this?
Dr. COWAN: Well, keep in mind that one thing that we do have working for us in the Gulf that is different than the Alaskan area is that the warm waters of the Gulf caused the biological breakdown of oil to occur more rapidly. So, it could take years, but maybe not as many years as the Exxon Valdez because things happen much more slowly in colder climates.
RAZ: I suppose what's most disturbing about all of this is that the best scientists in the world, including you, simply don't know, they just don't know what will happen.
Dr. COWAN: No, we don't. This is - it is unprecedented. The depth of the spill is unprecedented. And the complexity - there's probably not a more complex place in the Gulf of Mexico with respect to currents than right at the mouth of Mississippi. This stuff could actually go anywhere.
RAZ: That's Jim Cowan. He's a professor in the Department of Oceanography and Coastal Sciences at Louisiana State University. I spoke with him from Baton Rouge, Louisiana.
Professor Cowan, thank you so much.
Dr. COWAN: Thank you.
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