GRANTS PASS, Ore. - There are signs a recurring "dead zone" of low-oxygen water that is causing bottom fish and crabs to wash up dead on Oregon beaches is larger than in previous years and might be spreading north to Washington's Olympic Peninsula.
For the fifth year in a row, unusual wind patterns off the coast of Oregon have produced a large "dead zone," an area so low in oxygen that fish and crabs suffocate.
The dead zone, which appears in late spring and lasts a matter of weeks, has quadrupled in size since it first appeared in 2002 and this year covers about 1,235 square miles, an area about as large as Rhode Island, researchers said.
Low oxygen levels have been documented along 70 miles of coast, but dead fish and crabs have appeared on beaches along the Olympic Peninsula.
Komo 4 News reported last week that it could take hundreds of research trips off the state's coast to determine whether fish kills are the result of an oxygen-depleted dead zone.
This dead zone is unlike those found in the Gulf of Mexico and elsewhere - including Hood Canal - which result from fertilizer, sewage or runoff from hog or poultry operations carried by rivers. The Oregon zone appears when the wind generates strong currents carrying nutrient-rich but oxygen-poor water from the deep sea to the surface near shore, a process called upwelling.
The nutrients encourage the growth of plankton, which eventually die and fall to the ocean floor. Bacteria there consume the plankton, using up oxygen.
Jane Lubchenco, a marine biologist at Oregon State University, said the phenomenon did not appear to be linked to recurring El Nino or La Nina currents or to long-term cycles of ocean movements. That made Lubchenco wonder if climate change might be a factor, she said, adding, "There is no other cause, as far as we can determine."
The zone dissipates when winds shift.
The dead zones have been marked by intense bursts of upwelling that were followed by calm periods, when the water contains lower nutrient levels, said Jack Barth, professor of oceanography at Oregon State and, with Lubchenco, a principal investigator for the Partnership for Interdisciplinary Studies of Coastal Oceans.
This year, the upwelling started strongly in April, stalled in May and picked up again in late June. Following the upwellings, scientists found the oxygen levels lower.
It is not clear what effect the dead zone may have on future fish or crab catches, Lubchenco said. So far, she said, the dead zone has not formed until the Dungeness crab season has been nearly over.
Hal Weeks, a marine ecologist who leads the Marine Habitat Project for the Oregon Department of Fish and Wildlife, said the formation of the low-oxygen, or hypoxic, areas had so far caused "localized disruptions" in fishing but no overall decline in catches and no interference with recreational fishing.
Interesting anomaly?
In 2002 when the dead zone first appeared, Lubchenco said, she and other researchers dismissed it as an interesting anomaly. "But now, five years in a row, we are beginning to think there has been some sort of fundamental change in ocean conditions off the West Coast," she said, possibly because of changes in the jet stream caused by global warming.
"We know it's not pollution. It's not a toxic algal bloom. The simple fact is there's not enough oxygen," said Francis Chan, a research professor of zoology at Oregon State who has been measuring ocean oxygen levels.
Oxygen levels are generally lower in deeper water, said Lubchenco, but what is unusual about this condition is that it is moving into relatively shallow water, about 50 feet deep, and moving toward shore, where the richest marine ecosystems are.
Deep water fish, such as ling cod, wolf eels and rockfish, are showing up in Oregon tide pools, apparently driven toward shore by the advancing dead zone, said Lubchenco.
Komo 4 News reported that about 1,000 dead fish that washed up north of Ocean Shores were mid-column fish such as anchovies.
"If we continue like we are now, we could see some ecological shifts," Barth said. "It all depends on what happens with the warming and the greenhouse gases."
Comments