'Dead zone' startles scientists

'Dead zone' startles scientists

Ocean scientists took their first look Tuesday into the oxygen-starved "dead zone" spreading off the Oregon Coast and were shocked by what they saw: a lifeless wasteland of thousands of dead crabs, starfish and no live fish at all.

"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."

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Scientists suspect swings in the Earth's climate tied to global warming may be shifting wind conditions to bring about such grim results.

...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.

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.

Neuschwander was exhibiting the classic symptoms of domoic-acid poisoning, a condition that sends dazed marine mammals washing ashore in California as regularly as the spring tides.

They pick up the neurotoxin by eating anchovies, sardines and other sea life that consume algae that produce the acid. Although such algae have been around for eons, they have bloomed with extraordinary intensity along the Pacific coast for the past eight years.

Aquatic and marine dead zones can be caused by the process of eutrophication, triggered by an excess of plant nutrients (nitrogen and phosphorus) from fertilizers, sewage, combustion emissions from vehicles, power generators, and factories. In a cascade of effects, the nutrients trigger a bloom of phytoplankton at the bottom of the marine food chain, allowing zooplankton to proliferate. As phytoplankton and zooplankton die and sink below the photic zone where photosynthesis can occur, a bloom of natural bacterial degradation exhausts the water's dissolved oxygen.

Dead zones can also be produced by the natural event of river flooding. Large amounts of fresh water empty into the ocean forming a thick layer of fresh water atop the denser salt water, effectively forming a barrier between the ocean water and oxygen in the atmosphere. (Osterman, 2004)