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Scientists Study Gulf Fish for Signs of Oil Damage

December 31, 2010 at 12:00 AM EDT
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NewsHour Correspondent Tom Bearden talks to researchers who are assessing the long-term damage to the Gulf. In Alabama, scientists are examining whether damage done to fish larvae is linked to the oil spill.

JEFFREY BROWN: As we heard, scientists are still assessing the long-term damage to the Gulf.

NewsHour correspondent Tom Bearden recently caught up with researchers doing just that off the coast of Alabama.

TOM BEARDEN: On a bitingly cold December day, biology assistant Professor Anthony Overton braved the wind and the waves miles off the coast of Alabama, collecting microscopic baby fish. Again and again, Overton and his crew heaved a finely-meshed double net array over the side of a 27-foot aluminum boat.

This is one of eight excursions to catch menhaden larvae, the next generation of a species that is a prime source of fish oil for humans and food for predators. What happens to menhaden affects the entire food chain.

Overton and his colleagues are trying to find out if the BP oil spill and the dispersant chemicals that were used to break up the slick have done biological damage to this cornerstone species. Overton says this particular fish is abundant in the Gulf.

ANTHONY OVERTON, East Carolina University: The adults have probably been exposed much of the oil throughout the spill region, and if there’s any oil still left around in the surface waters, then most likely their eggs and larvae, which are spawning right now, would be exposed. So it spans such a large coverage area. If we were to see any effects on a particular species, we’d most likely see it with that species.

TOM BEARDEN: They allowed the nets to sink down to about 90 feet, then winched them back up at two-minute intervals. Overton then sluiced what the net had trapped into plastic sample jars. They did it six times in six different, carefully-recorded locations.

ANTHONY OVERTON: We want to make sure that we sample the entire water column so that we capture larvae throughout the water column. So that’s why it’s designed such that we sort of pull the net up through the water.

TOM BEARDEN: They’re particularly focused on how the tiny fish’s genetic structure might have been affected.

ANTHONY OVERTON: Genes are responsible for everything in terms of protein production, development. They’re responsible for every process that occurs in the body. So any major changes or particularly potential changes in gene expression could cause major impact in terms of the development and possibly the survivability of a fish.

TOM BEARDEN: Back on shore, Overton prepared the day’s catch for shipment back to East Carolina University in Greenville, North Carolina. Over the next several months, faculty and students will carefully sort, classify, and examine the menhaden larvae, cataloging any damage they might find.

Back at ECU, the project has actually been under way since October, when Assistant Professor Ed Stellwag started what amounts to a small fish farm. The research team needed another species of fish larvae that could be exposed to controlled amounts of oil and dispersants in the laboratory to compare with the fish taken from the Gulf.

Stellwag set up an array of fish tanks to spawn zebrafish, a small, well-studied species that produces new larvae every day. The larvae fall to the bottom of the tanks, where marbles prevent the adults from eating them. Stellwag retrieves them with a simple siphon.

ED STELLWAG, East Carolina University: We’re getting about 800 to 1,000 embryos, and when we culture them — and of course we’re going to continue to grow those until we build up a large enough stock. And then we can each day look at them and monitor their progress.

TOM BEARDEN: So are you kind of a midwife for zebrafish?

ED STELLWAG: Yes. At this point, my students and I, yes. These were spawned on Sunday, and what I’m going to show you here is how — because some of them have died.

TOM BEARDEN: What killed some of these?

ED STELLWAG: They’re just naturally developmentally defective.

Nothing in particular.

And what happens, though, is that when they die, they become very susceptible to mold or fungus. If the fungus starts to spread, it can wipe out a lot of them.

The eyes are prominent at this stage, and they’ll continue to be that for a while.

TOM BEARDEN: Stellwag hopes the investigation will provide useful information on how best to deal with the next oil spill.

ED STELLWAG: It’s possible that what we could do is be able to give some information back to the people who are deciding about the way to deal with oil spills, as to what the best approach might be. Should we use dispersants, what effect is that going to have?

TOM BEARDEN: Could it also help understand the effects on humans who live in that environment?

ED STELLWAG: Well, certainly. I mean, we’re animal species, and we’re part of that ecosystem. And we’re going to consume products from that ecosystem, and even after the acute effects have diminished.

You know, there are tarballs which are going to be present, and they’re going to leach out at these products. I think that we certainly could see these effects over the long term.

TOM BEARDEN: The project hopes to publish its first results next summer.