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Public Radio's Environmental News Magazine (follow us on Google News)

Old Oil Still Haunts: Exxon Valdez Revisited

Air Date: Week of

Nearly ten years after one of the worst oil spills in history, new research shows that oil still hidden in beach gravel and sediment may still be affecting the health of the environment.


CURWOOD: It's Living on Earth. I'm Steve Curwood. It was nearly 10 years ago, in March of 1989, that the Exxon Valdez oil tanker smashed into a reef in Alaska's Prince William Sound and spewed more than 10 million gallons of crude oil onto waterways and beaches. Over the last decade, the region's wildlife and economy have seemed to have slowly been recovering. But there have also been mysterious fluctuations in the populations of many animals, And concerns that oil may still be having an impact. Now researchers have found what they say is convincing evidence that old oil hidden in beach gravel in sediment in the Prince William Sound area affected the health of wildlife years after the spill. Jody Seitz has our story.

(Blasting sounds; voices in background)

SEITZ: This is the sound of high-powered air knives blasting crude oil and asphalt off beaches in Prince William Sound 8 years after it was deposited by the Exxon Valdez oil spill. Experts had long argued that the oil remaining in beach sediments was no longer harmful to wildlife. But residents of the nearby community of Chaneka Bay, who live by hunting and fishing, were never convinced, And they finally won this long-delayed cleanup. Now, the combined results of both laboratory and field studies have shown their instincts were right. Scientists have discovered that weathered oil gives off compounds which are toxic to fish.

HEINTZ: As the oil weathers, basically what you get are these heavier and less mobile compounds remaining in the oil that's deposited. And as it turns out, those compounds are the ones that unit per unit are the most toxic compounds.

SEITZ: That's Ron Heintz. He and other scientists with the National Marine Fisheries Service Ocbay Lab found that the old spilled oil is more toxic than anyone ever imagined. Weathered oil in the environment never got much attention in the past. But Heintz and other government researchers started to get suspicious in the early 1990s. Most of Prince William Sound's wild pink salmon spawn in the intertidal areas of streams, many of which had been contaminated by crude oil in 1989. Scientists weren't surprised to see dead salmon eggs in these areas in 1989 or even 1990, but they found many more dead salmon eggs than usual all the way through 1993, long after most of the light aromatic compounds had dissipated. They began to wonder whether the problem was being caused by the heavier compounds, which persist as the oil slowly decomposes.

(Running water)

HEINTZ: Okay, so this is our latest iteration of the pink salmon exposure system. Thirty incubators operating right here, And there's about 8,000 eggs in each incubator.

SEITZ: At the remote little Port Walter Research Facility in a pristine area of southeast Alaska, Heintz and his colleagues begin exposing salmon eggs to controlled amounts of weathered north slope crude oil.

HEINTZ: Water percolates up through this column of oil gravel and flows out the top of this chamber, falls down into this second chamber, where it percolates up through another column of clean gravel that's seeded with developing pink salmon eggs. So the pink salmon are exposed to the water that's been contaminated by percolating through the oil gravel.

SEITZ: The researchers discovered early on that the eggs didn't have to touch oiled gravel to be affected. Some eggs were killed merely by oil circulating in the water at concentrations as low as 17 parts per billion. At higher doses other eggs showed sublethal effects, such as abnormal development of gonadal tissues, the cells that eventually become eggs and sperm. As they continued their experiments, the researchers found that the longer the oil weathered, the more deadly it became. Oil which had weathered 1 year killed salmon eggs at concentrations as low as 1 part per billion. Dr. Stanley Rice, program manager at the Auke Bay lab, explains that traces of oil in the water are attracted to the fatty yolk of fish eggs. When they encounter an egg, the heavier compounds can enter easily, And once inside the egg can't get rid of them.

RICE: When a tiny particle of oil comes along and bumps into the egg, it's absorbed, And it's trapped. If we get exposed to a piece of oil, we'll metabolize it and get rid of it. But the fish egg, it's in the lipid and it just sequesters it, And eventually the dose builds up within the egg. And then you get these long-term effects.

SEITZ: Often, the effects of the oil couldn't be detected until the fish were older. The fry that survived exposure as eggs grew more slowly and fewer of them returned from the ocean as adults. Those that did return were smaller than normal. Similar effects were found in herring eggs exposed to weathered oil in the lab. Adult herring also showed suppressed immune systems and vulnerability to a virus, the same virus which caused the Prince William Sound herring population to crash in 1993. The Auke Bay studies on weathered oil could add a significant new item to the already long list of concerns about oil spills in Prince William Sound and elsewhere. In the past the concerns centered mostly on the lighter molecules in crude oil, some of which are highly toxic, but which also dissipate quickly. Dr. Rice says the new findings show a far more complex picture.

RICE: We are right in the forefront of thinking it was the light ends that were the bad guys, And they certainly are in the first weeks and months of the spill. But later on the persistence takes hold. Being more toxic is not a big deal if you don't hang around. But when you hang around literally not for days, months, but years, there's a lot of time for that toxicity to be a factor.

SEITZ: And there's a lot of weathered oil hanging around. Oil is the most common contaminant in aquatic environments. The new study of the toxicity of old weathered oil will face tough scrutiny, And will probably need to be reproduced elsewhere before it's widely accepted.

MAKI: If indeed those levels are valid, we have some very serious concerns about what it implies in the real world.

SEITZ: Dr. Alan Maki is environmental advisor to the Exxon corporation. He has also served on the US Environmental Protection Agency's Science Advisory Board and conducted his own research on pink salmon after the Valdez spill. He says it's difficult to believe that 1 part per billion of weathered oil could cause the damage reported by the Auke Bay researchers.

MAKI: The number is directly in conflict with a large number of published papers, research programs done by other agencies. Similar studies indicate that effects don't occur at that low level, And we have serious problems in understanding how those effects could really be reported at what are basically background levels.

SEITZ: Other researchers who've advised Exxon are also skeptical. Dr. Ernie Brannon, director of the Aquaculture Institute at the University of Idaho, says the lab experiments don't represent what actually happens in the streams. Dr. Brannon also questions the field research would set off the alarms about the higher salmon mortality in the first place. He suggests the eggs were sampled too soon after spawning, And that handling, not oil, killed the eggs. The scientists at Auke Bay believe the egg sampling was done properly. They say they found results no one had ever found before, because they did long-term experiments that had not been done before. No one knows where or how much oil remains in the beaches of Prince William Sound, And there's a lot of uncertainty about its effects on wildlife populations. Researchers have continued to see the mark of contamination in several species that inhabit the oiled areas. The Sound's herring and salmon populations crashed in 1993, but researchers have still never linked those crashes to the oil spill, And they don't think the Ocbay findings mean Alaskans are in danger of losing their salmon runs from oil pollution. But it probably does erode the populations, says Brian Bue of the Alaska Department of Fish and Game.

BUE: Salmon are a very resilient species. There's an effect but it's not catastrophic.

SEITZ: For its part, the state of Alaska seems to be taking the new findings seriously. Recently, industry had proposed relaxing the state regulations for oil discharges in water. But Ocbay research suggests weathered oil could have a toxic effect at levels less than a tenth of the current standard. So while it takes a closer look at the research, Alaska has decided at least not to lower its water quality standards. For Living on Earth, I'm Jody Seitz in Anchorage.



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