And certain beaches in Prince William Sound have far more oil than anyone thought possible a dozen years after the Exxon Valdez tanker struck Bligh Reef, according to a rigorous survey conducted last summer.

Much of that oiled sediment underlies flat productive shore of the western Sound, homeland to mussels and clams and other intertidal life, said federal chemist Jeff Short of Auke Bay Laboratory in Juneau.

"It's more than it looks," he said.

Other studies done as part of a continuing scientific review of the oil spill have documented problems among certain species that forage on the nearby sea floor.

The findings were presented Tuesday by scientists during the opening session of the state-federal Exxon Valdez Oil Spill Trustee Council's annual workshop. They suggest that lingering oil is leaching into the food chain, where it hurts local populations of sea otters and harlequin ducks.

"We did indeed find quite a lot more oil than we expected to see," Short said. "Most of the subsurface oil was in the fresh oil category, and by fresh oil I mean chemically, compositionally; it hasn't really changed very much since late in the summer of 1989."

Exposure to this oil may no longer threaten overall animal populations. But sea otters and harlequin ducks have been ingesting hydrocarbons and apparently suffering damage, according to reports by biologists Brenda Ballachey of the U.S. Geological Survey and Dan Esler of Simon Fraser University in British Columbia.

This damage includes liver problems in otters, including abnormal tissues found last summer during endoscopies and biopsies conducted in the field, Ballachey said. Otter and duck numbers in oiled areas have continued to decline, while populations in nonoiled bays fare much better.

The tanker hit the charted reef in March 1989, dumping 11 million gallons that spread throughout much of the Sound and beyond. That this oil still has the power to harm wildlife, even if on a limited scale, is one of the most disturbing and startling findings to come from a decade of research and monitoring, several scientists said.

"The oil was quite a bit more persistent and quite a bit more toxic than we thought in 1989," Short told the audience during a question-and-answer period.

An Exxon Mobil official and a Maine chemist dismissed the idea that the spill still causes significant damage to life in the Sound.

"What science has learned in Alaska and elsewhere is that while oil spills can have acute short-term effects, the environment has remarkable powers of recovery," said company vice president Frank Sprow in a statement e-mailed from company headquarters in Irving, Texas.

Bowdoin College biochemist David Page, who has conducted studies for Exxon, said he was skeptical of Short's findings.

"For at least the last seven years, natural factors in PWS have been the major factor in governing ecological changes," he added in an e-mail.

The meeting continued Wednesday at the Egan Convention Center in Anchorage with discussions about how a long-term research program to monitor the Gulf of Alaska could tie in with other research from Southeast Alaska and the Bering Sea.

As about 100 scientists and others gathered in a basement hall on Tuesday, seven biologists gave reports on lingering oil and the status of fisheries, birds and marine mammals in the spill zone. Included was a presentation on the beach survey, conducted by Auke Bay Lab with $572,000 from the Trustee Council and help from the Bureau of Economic Geography at the University of Texas.

Over 90 days last summer, a field crew visited 91 sites along about five miles of beaches, covering about 20 percent of the area classified as heavily or moderately oiled between 1989 and 1993, Short said. They dug 6,775 pits at random locations, then dug dozens of additional pits every time they found oil to calculate how far it spread.

To gather enough data to make a meaningful estimate of how much oil remained and how fast it was weathering and leaching away, Short and the other investigators hoped to find oil at least 1 percent of the time.

Instead they discovered oil at 53 of 91 sites, in 568 different pits - about eight times more often than they expected. Although most of the pits were "lightly oiled," about 20 contained oil that looked as fresh as that just a few weeks after the 1989 spill - "highly odiferous, lightly weathered, and very fluid," they wrote in a preliminary report.

In the end, Short and his team estimated that about 10,000 gallons of Exxon Valdez crude remains buried under 26 to 28 acres spread along about 4.3 miles of shoreline scattered throughout the area, according to preliminary figures released on Monday. It appeared to be declining at 26 percent per year.