NEWPORT, Ore., Aug. 17 — On the north shore of Yaquina Bay rests the rusty fishing fleet of this small Pacific port, scores of boats whose captains seek salmon or rockfish, shrimp or crab.
Directly across the bay, on the south shore, sits the Hatfield Marine Science Center, a small campus of Oregon State University that provides a seaside outpost for scientists who study the water and the life within it.
The natural divide has seemed particularly fitting this summer, with the two groups, who rarely share the same view anyway, drawn farther apart by a recent discovery. In a large section of shallow ocean water near the shore, scientists at the university measured record-low levels of oxygen this month, so low that most marine life cannot be sustained there. Countless crabs and other crustaceans have died, and fish have simply disappeared from some spots.
Scientists call such an area a “dead zone,” and some suggest that this one could portend broader, troubling environmental changes linked to global warming.
There is little dispute that the dead zone exists; the disagreement centers on whether it matters much. In a state where fishermen are already accustomed to strict regulation, fights with environmentalists and attention from academics, many of them are having none of the notion that there is a larger problem.
“They say it’s global warming and it’s Bush’s fault, and it just goes on and on and on,” said Bill Wechter, 53, a crabber who said he had been working here since 1978, had 500 traps stretching north from Newport and had suffered no losses. “Everybody’s guessing.”
This is the fifth straight year in which a dead zone has appeared here, but scientists say that this one is by far the biggest, covering as much as 1,200 square miles, and that the oxygen levels have been startlingly low in places.
Those low levels are caused by persistent northerly winds that push nutrient-rich water into shallow areas — a process known as upwelling — without being offset by southerly winds that typically flush out the water and effectively keep it from becoming overfertilized. Dead zones are common around the world, with the Gulf of Mexico, Lake Erie, Narragansett Bay and Long Island Sound experiencing them on occasion. But most often they are caused by local pollution problems, including runoff containing fertilizer or sewage.
Adding the recent observations off Newport to findings that date from 2002, when a summertime dead zone was first documented here, some scientists say changes in wind patterns could indicate a growing disparity between rising land temperatures and cool ocean temperatures. Such a condition has long been predicted in some regional models on the effects of global warming, said John A. Barth, an Oregon State oceanographer who is among a group of scientists of various disciplines studying the Oregon coast.
But the fishermen say they know the ocean best: they spend their lives working it rather than writing research papers about it. Changes in ocean conditions simply require adjustment, they say, whether that means shortening lines or fishing closer in or farther out.
By and large, they are not worried. They cite the state’s record 2005 crab harvest, 33.7 million pounds, and another strong harvest, 27.5 million pounds, in the season just ended.
“There’s all kinds of cycles in the ocean,” said Jim Emory, a 41-year-old fisherman whose boat is named Monde Uni. “It is what it is. It’s an opportunity.”
Some scientists, too, are being cautious. Jane Lubchenco, a zoologist who specializes in marine ecology at Oregon State and who has long been outspoken about global warming threats, is among those who say that while the findings here are fascinating, more data, collected over a longer period of time, are needed.
“We can’t say with absolute certainty that this has never happened before,” said Ms. Lubchenco, former president of the American Association for the Advancement of Science, who has worked at Oregon State since 1978.
The other day Ms. Lubchenco and other scientists boarded the Elakha, a 54-foot boat used to research close to shore. Sea lions lurched past buoys marking testing equipment. Cormorants flew inches above the surface.
Tests that day showed oxygen levels in the northern part of the dead zone improving, perhaps reflecting a slowdown in the upwelling. [Tests in the central and southern parts this week, on the other hand, continued to show very low readings.]
Francis Chan, a marine ecologist at Oregon State who has been measuring the oxygen levels off the coast since 2002, said a scientist here was sometimes viewed as having a political agenda and lacking a real understanding of the ocean. Yet Mr. Chan, who takes samples digitally but also collects water with the glass Winkler bottles that scientists have used for decades, points to charts that he said he had compiled from oxygen readings recorded over the last half-century.
“People say, ‘Oh, there’s always been dead zones,’ ” Mr. Chan said, “but when I look at the entire data we have, I just don’t see these numbers in the historical record.”
Mitch Vance, the shellfish project leader for the Oregon Department of Fish and Wildlife, is one of those who believe far more data are needed.
As for the often divergent views among the people who share Yaquina Bay and the ocean it meets, Mr. Vance said, “It depends on how many fishermen and scientists you get in a room; that’s how many opinions you’re going to have.”