Valdez spill leaves lasting oil impacts.

On March 24, 1989, the Exxon Valdez supertanker ran aground in Alaska's Prince William Sound. Ruptured holds released a fifth of the vessel's oil -- some 10.8 million gallons of Prudhoe Bay crude. Over three years, Exxon, the state, and the federal government coordinated a $2.5 billion cleanup- sometimes involving 10,000 workers.

At an oil-spill symposium in Anchorage, Alaska, last week, scientists reported that both the pollution and its cleanup took a heavy toll on south central Alaska's marine ecosystems. And though many plants and animals are recovering, notable exceptions exist. The meeting marked the first general release of government-funded research on effects of the Valdez spill, observes Bruce A. Wright of the National Marine Fisheries Service in Auke Bay, Alaska, a coordinator of spill-damage assessment research.

Federal law requires that state and federal agencies name "trustees" to establish public claims against firms that damage natural resources. Trustees managing the case against Exxon prohibited their researchers from discussing spill effects prior to court approval, on Oct. 1, 1991, of a $900 million settlement from the Irving, Texas-based Exxon Co. USA. Planning for this meeting began just after that, Wright says.

No one knows exactly how much Exxon Valdez oil ended where. The National Oceanic and Atmospheric Administration (NOAA) is attempting to "reconstruct" the oil's trajectory and estimate its removal by plugging both weather data and observations from spill sites into sophisticated computer models.

Preliminary analyses indicate that 20 percent of the oil evaporated -- 8 percent on day one alone, according to Douglas A. Wolfe, chief scientist of NOAA's ocean assessments division in Rockville, Md. He says another 50 percent probably degraded on beaches, in the water, and within tidal sediments; an estimated 12 percent now lies in deep (nonbeach) sediments, and some 3 percent remains on intertidal shores, usually as tarry deposits.

Mechanical water skimmers removed some 8 percent of the oil. Wolfe estimates that cleanup crews recovered 6 percent more from sand and sediment or dispersed this oil into the water, where less than 1 percent remains.

"Skimming was operation heartbreak... [because] not a lot of oil was picked up," recalls Coast Guard Vice Admiral Clyde E. Robbins, who served as the cleanup's initial, federal on-scene coordinator. Cleaning heavily oiled shorelines proved a more visible success, he says. Hot-water washing and treatment scoured blackened rocks bright again. Displaying before-and-after shots of one Smith Island beach he visited (see photos), Robbins said, "I swear, I never expected it to come clean like that."

The frequently used high-pressure, hot-water washing also "annihilates a lot of marine life that otherwise survive the spill," observes Alan J. Mearns of NOAA's ecological recovery monitoring program in Seattle. Rockweed, a brown alga, proved its most prominent victim. Formerly constituting up to 90 percent of the intertidal plant mass in some areas of Prince William Sound, it virtually disappeared in many areas subjected to hot water, scientists reported. And especially in higher tidal zones, rockweed's recovery remains slow.

But it was oil that devastated the bird population. Oil killed perhaps half a million- more than 10 times as many as in any other U.S. spill, says D. Michael Fry of the University of California, Davis. Notable casualties included perhaps 11 percent of the 8,000 bald eagles in Prince William Sound. However, say scientists with the U.S. Fish and Wildlife Service, that population may already have recovered.

The same has not proved true of harlequin ducks. Fry said half of those living in the oiled regions were killed outright, and most that survived have failed to breed. Dennis Heinemann of Walcott and Associates in Alexandria, Va., reported that up to one-third of the areas adult common murres - diving seabirds that resemble mini-penguins - died directly from the spill. Even more troubling, he noted, breeding in colonies affected by the oil has virtually ceased.

Other researchers described signs of "functional sterility" in pink salmon and herring from heavily oiled areas. While these fish continue to spawn, certain age classes have produced dramatically increased numbers of dead eggs or severely realformed hatchlings - such as live young with curved spines or no jaws.

A pilot study by Evelyn D. Biggs of Alaska's Department of Fish and Game in Cordova, for example, suggests that year-old herring who lived in oiled near-shore waters in 1989 produced just half the viable young last year of similar herring from unoiled waters. So dramatic an effect this long after a spill "has never been documented before," she says and might indicate damage to cells producing sperm and eggs. If true, says Biggs, these fish would be "reproductively impaired for the rest of their lives."

Organizers of last week's meeting had invited Exxon to present research - and to share in planning the symposium. The company chose instead to unveil its data in April at an American Society for Testing and Materials (ASTM) meeting in Atlanta. ASTM offers a more "independent" forum, says Dennis Stanczuk of Exxon in Anchorage. Moreover, he contends, the Anchorage meeting's "stated purpose was to help make decisions on how [damage] settlement funds will be allocated." As Exxon is not part of that process, he says, "it would be inappropriate to take part."

L.J. Evans of Alaska's Department of Environmental Conservation in Anchorage disagrees. An organizer of last weeks meeting, she says the symposium was never intended to affect spending of the $900 million settlement.

Exxon has invited trustee-funded researchers to report at ASTM, however, "and we will," Wright says. -J. Raloff