"It was a real eye-opener for all of us," said Hal Weeks, a marine ecologist with the Oregon Department of Fish and Wildlife. "I don't think anybody expected this sort of thing."
Dead Dungeness crabs off Cape Perpetua, just south of Yachats, "were like jellybeans in a jar. You just can't count them, there were so many."
Oxygen
levels in places along the central Oregon Coast have sunk to the lowest levels
ever recorded on the West Coast of the United States, said Francis Chan, a
marine ecologist at Oregon State University and the Partnership for
Interdisciplinary Studies of Coastal Oceans, an alliance of research
institutions. Scientists suspect swings in the Earth's climate tied to global warming may be shifting wind conditions to bring about such grim results.
Seawater turns deadly for marine life when concentrations of the dissolved oxygen they breathe fall below about 1.4 milliliters per liter. On Monday, Chan measured a concentration of .05, or almost 30 times below the lethal level, about 90 feet below the surface.
It is very close to a complete absence of oxygen, a situation rarely known in the world's oceans, said Jane Lubchenco, a professor of marine biology at Oregon State. New bacteria that take over when oxygen disappears are known to release poisonous hydrogen sulfide gas.
"We never suspected that could happen here," Lubchenco said.
This is the fifth consecutive summer that a layer of low-oxygen water has blanketed the ocean floor along the Oregon Coast, and it has rapidly turned into the most severe episode so far. The layer this year is thicker, lower in oxygen and far larger, covering at least four times more area than in previous years, Lubchenco said. It stretches at least from Lincoln City to near Florence, and the conditions appear to be worsening.
Oregon
owes its rich marine environment to water welling up from the deep ocean, rich
in nutrients but low in oxygen. The difference this year is that winds from the
south have been too unreliable to cycle surface water with more oxygen into the
depths, Chan said. Instead, winds from the north are driving the oxygen-poor
waters into shallow reaches closer to shore. As tiny marine organisms sink below
the surface, their decay sucks more oxygen from the water. Scientists who have
watched the eerie phenomenon repeat itself now wonder whether climate changes
linked to global warming are causing changes in the jet stream, which drives
Oregon winds. Though they had tracked the oxygen concentrations, they did not know what was happening to sea life until Tuesday, when a video camera aboard a remote-controlled submarine operated by the Oregon Department of Fish and Wildlife gave them a look. Rocky stretches of ocean floor off Cape Perpetua that normally teem with crab, rockfish, anemones and more had turned into ghostly graveyards. Dead crabs rocked with the water, fat pink worms that usually live in the seafloor instead lay dead on the surface and starfish had begun rotting away.
It
is unclear what it means for fishermen and crabbers, he said. There have been
reports of some anglers being skunked in usually reliable fishing spots. Chan
said he had heard from a salmon fishermen who caught a flounder, a bottom fish,
far above the bottom, where it may have been avoiding the suffocating layer. But
the last few crab seasons have brought record catches despite the appearance of
dead zones, said Al Pazar, a fisherman from Florence and member of the Oregon
Dungeness Crab Commission. "The short answer is, 'yes, I'm concerned,' " he
said. "The long answer is, 'we'll have to watch this and see what happens.' "