Pollution in Puget Sound may be claiming another victim.
It's not another microscopic crustacean, or some ugly flatfish of little commercial value, like the English sole, that spends its life half-buried in mud.
This time it's that regional icon, that king of Northwest waters, the salmon.
Recent research by a team of government scientists suggests juvenile chinook salmon - smolts - may be picking up the seeds for an early death in the North Pacific as they migrate through contaminated Puget Sound estuaries like Seattle's Elliott Bay and Tacoma's Commencement Bay.
Until recently, scientists assumed pollution in the Sound posed little risk to salmon. Most of the sea creatures shown previously to be harmed by pollution in urban bays spend their lives on the bottom, in sediments laced with toxic chemicals.
Salmon smolts don't live on the Sound's floor. What's more, they spend just a few days or weeks in the estuaries, pausing to acclimate to salt water on their way from rivers to the ocean.
But research at the federal Northwest Fisheries Science Center in Seattle has shown that's enough time for the 4-inch-long fish to accumulate elevated levels of toxic chemicals in their organs and body fluids - levels that persist for months, perhaps longer.
Studies show those elevated levels impair the smolts' immune systems and stunt their growth. The chemicals also may cause cancer or reproductive problems as the fish mature, said Usha Varanasi, director of the center's Environmental Conservation Division.
"All of their systems are more vulnerable, and at more risk because they are in the developmental stage," she said.
Most of the research so far has centered on Seattle's Duwamish Waterway, where the Green River pours into Elliott Bay. While fish from Tacoma's Puyallup Waterway and Everett's Snohomish River estuary have been included in some studies, less is known about the nature and extent of the problem there.
But the possible implications for Puget Sound's salmon stocks warrant concern and further study, Varanasi said.
Others agree. "In Puget Sound, most of the major fish production we have passes through these heavily developed areas," said Hal Michael of the state Department of Fisheries.
Kathy Fletcher, executive director of People for Puget Sound, said the studies should prod citizens and officials to redouble efforts to limit toxins that pour into the Sound from factories, sewage-treatment plants and storm water.
"I just can't speak strongly enough about how significant I think this work is," she said.
SCIENTIST SHOWED EARLY EVIDENCE
The scientists doing the work hail from the same government research outfit once headed by Donald Malins. After Carl Sagan, he may have been the best-known scientist in Western Washington in the early 1980s.
It was Malins, a dapper man with a British accent, whose research - and flair for publicizing it - helped draw attention to the polluted state of Puget Sound nearly a decade ago. With cameras rolling, he would pull English sole up from polluted urban bays, slice them open and expose their tumor-riddled livers.
Malins left in 1987. But the center, a branch of the National Oceanic and Atmospheric Administration (NOAA), has continued to refine and build on the work he began, said Varanasi, his successor. Most of that work has been out of the limelight, as public attention has shifted from Puget Sound to other environmental ills.
The center's salmon work began six years ago, with comparative studies of smolts taken from the Duwamish Waterway, the relatively pristine Nisqually estuary in south Puget Sound, and salmon hatcheries on the rivers upstream from both.
So far, scientists have found:
-- Higher levels of aromatic hydrocarbons - toxic chemicals associated with oil and other fossil fuels - and polychlorinated biphenyls (PCBs) in the stomach contents of smolts taken from urban estuaries. Their stomachs contained amphipods - small shrimp-like animals - associated with bottom sediments, suggesting the chemicals probably are getting into the fish through the food chain.
-- Higher levels of some of those same compounds in the liver and bile of Duwamish salmon - levels that didn't change much in three months after the fish were moved from the polluted estuary to laboratory tanks.
-- Enzyme activity associated with exposure to chemical contaminants in Duwamish smolts that is almost double that found in Nisqually smolts. Varanasi said such increased activity has been linked to reproductive problems in English sole, but such a correlation has not yet been established for salmon.
-- Greater levels of genetic damage that can be the first step toward cancer in the livers of Duwamish fish.
-- Weakened immune-system response among Duwamish smolts. Fish from that estuary, the Nisqually and the hatcheries showed similar immune responses when exposed initially to a foreign compound, Varanasi said. But, when exposed to that compound a second time, the Duwamish fish produced far fewer cells capable of producing antibodies to fight back.
It's somewhat analogous to inoculating humans against measles, only to have them remain susceptible to the disease when exposed again. "The fish from the Duwamish don't seem to `remember,' " Varanasi said.
Scientists injected healthy hatchery fish with the same contaminants found in the Duwamish sediments and got similar results, she added. Damage to the smolts' immune systems could have serious implications for their survival upon first reaching the ocean, where they are exposed to new parasites and diseases.
-- Slower growth over a three-month period in fish taken from the Duwamish Waterway. Smolts that were hatched at the same time but taken directly from the state's Green River hatchery to saltwater laboratory tanks - fish not exposed to the toxic chemicals in the estuary - grew 20 percent more.
"Smaller fish tend to get eaten by bigger fish," Varanasi said.
She can't say conclusively that the health problems scientists have discovered mean more fish are succumbing to predators or disease at sea. Nor can she say for certain that fewer salmon are surviving to return to Puget Sound rivers to spawn because they were exposed to pollutants in the estuaries as juveniles.
Those aren't easy questions to answer. The North Pacific is a melting pot for salmon from all over North America and Asia. Fish from specific watersheds would be difficult to find or study.
IT'S SURVIVAL OF THE FITTEST
And those fish that do return to Puget Sound to spawn are those least likely to display health problems. "The fittest have survived," Varanasi said.
Recreating what might be happening once the fish leave Puget Sound in the laboratory isn't easy. Scientists still are learning how to hold salmon in tanks more than a few months without significant mortality.
Also, Varanasi said, while scientists know the levels of toxic chemicals found in the Duwamish Waterway harm salmon, they still don't know whether the lower concentrations found in other urban bays are causing similar damage.
"Each year we are answering a question," she said, "and coming up with two more questions."