ANCHORAGE - A killer whale that was stranded and died last summer outside Cordova was carrying high levels of industrial poisons in its body, offering yet more evidence that pollutants produced thousands of miles away continue to accumulate at the top of Alaska's marine food chain.
These chemicals may now be another factor pushing a genetically unique family of Prince William Sound whales closer to extinction, according to area whale biologists and environmentalists.
"It's more of the same bad news," said biologist Craig Matkin, of the North Gulf Oceanic Society and the region's leading killer whale researcher.
The contaminants found in the dead whale were PCBs, or polychlorinated biphenyls, and the pesticide DDT, chemicals banned or restricted in the United States for decades but still produced in some Asian and Third World countries.
Transported across the globe on air and ocean currents, the contaminants infiltrated Alaska's food chain and have been documented at elevated levels in a wide range of animals for years - sea otters, seals, walruses, peregrine falcons, northern fur seals and bald eagles. As the chemicals move up the food chain, they concentrate and build in fatty tissues.
As a result, among 77 killer whales tested in the Gulf of Alaska between 1994 and 1999, the highest levels appeared among animals that eat only marine mammals, the type known as transients. Among 10 killer whales sampled in 1999 and 2000, several transients appear to be among the most contaminated marine mammals ever measured.
The whale, part of the group known as AT1, died last July in Hartney Bay. He was a closely studied harbor seal predator nicknamed Eyak. He had concentrated PCPs at about 370 parts per million and DDTs at about 470 parts per million in its tissues, according to chemist Gina Ylitalo, of the National Marine Fisheries Service's contaminants lab in Seattle.
Another transient male from the Gulf of Alaska had the highest levels ever measured in Alaska waters - about 651 parts per million PCBs and about 1,003 parts per million DDTs, according to Matkin's report. That whale, unrelated to the Sound's AT1 group, had a dorsal fin that was bent over, a sign of ailing health among killer whales.
By comparison, the U.S. Food and Drug Administration standard for PCBs in fish for human consumption is 2 parts per million and the limit for DDTs is 5 parts per million.
The results were released this spring as part of an annual report by Matkin and four other authors on the status of the Sound's killer whales for the state-federal Exxon Valdez Oil Spill Trustee Council.
Similar levels found recently in killer whales in the Pacific Northwest prompted leading biologist Peter Ross and four others to write in Marine Pollution Bulletin that "killer whales in British Columbia can now be considered among the most contaminated cetaceans in the world."
Scientists don't know how the substances affect the long-lived, slow-reproducing killer whales. Whether such elevated levels contributed directly to the death of the 5-ton, 24-foot whale isn't known, Matkin cautioned.
But comparable contaminant loads have been linked to reproductive failures in beluga whales of the industrialized St. Lawrence River estuary, die-offs of striped dolphins in the Mediterranean Sea and European harbor seals.
"It's clearly in the range of potential health risks," Matkin said. "It's scary stuff."
Whatever the cause, the death of Eyak furthered the decline of the AT1 group, an extended family of whales that lost 11 of 22 members in the three years after the Exxon Valdez oil spill. These whales, which have never been seen associating with other transients in the region, have not produced any offspring since before the spill.
"The upshot is that they're disappearing so fast that I don't know what we can do for them," Matkin said. "We've been debating about whether to try to get them listed under the Endangered Species Act."