Dreaded ocean 'dead zone' returns along coastal stretch.

Byline: Winston Ross The Register-Guard

FLORENCE - For an unprecedented sixth straight year, a low-oxygen "dead zone" is taking shape along a miles-wide swath of ocean real estate between Florence and Newport, choking off any marine life that isn't fast enough to escape it.

And, because last year's dead zone grew so large and killed so many sea creatures, the return of "hypoxic" or low-oxygen conditions this year could mean that ocean life on the Oregon Coast is affected for decades.

"The system is showing early signs of rebounding, but a full recovery may be a long way off," said Jane Lubchenco, an Oregon State University professor of marine biology and a leading researcher on the topic. "This marine ecosystem may take as long to recover as the terrestrial ecosystem did from the eruption of Mount St. Helens."

Researchers took to the sea last year with an underwater camera to survey the results of the dead zone, and found the ocean floor littered with thousands of dead crabs and other animals in a vast underwater graveyard.

This year, the dead zone is forming over an area that starts about a mile off the coast, extending another 10 to 15 miles out to sea, in an area roughly from Florence to Newport.

When researchers first discovered that low-oxygen water was killing fish and shellfish off the Oregon coast in 2002, they considered it an anomaly - without explanation but also without any indication that it would persist. There are other parts of the world, such as the Gulf of Mexico, where hypoxia is a recurring event, but it had never been recorded here before 2002.

The consistent return of this dead zone means that something big may be happening in Oregon's near-shore ocean, something that could permanently alter the marine ecosystem and the communities that rely on its resources.

Video footage taken of the reefs affected by last year's hypoxia - which was by far the most dire of any preceding events - showed a dramatic loss of species diversity, Oregon State University researchers say. Most sea stars, sea cucumbers and other bottom-dwellers have yet to rebound.

"Some rockfish have moved into the area, but the bottom-dwellers that provide the habitat and food for rockfish and a diverse array of other species are slow to return," Lubchenco said.

No one knows if hypoxia will persist here. And past dead zones have only arrived for a few summer months. The state's most valuable fishery, Dungeness crab, takes place largely from December until early Spring, and has yet to show any signs of being affected.

Fish that are caught in the summer months aren't necessarily a great indicator either, said Francis Chan, an OSU marine ecologist, because fishermen are adept at avoiding areas where there's nothing to catch. But fishermen dread reports of dead zones, fearing it will make consumers expect seafood markets to be affected and scare off sportfishing customers.

Only more time and more research can answer what hypoxia's long-term effects will be, Chan said, and whether the dead zones can be linked to global warming. In each of the more recent years, the recurring dead zone has strengthened the possibility that climate change is at play. But there's no empirical evidence to draw a decisive conclusion, leaving scientists only to speculate.

What is certain is that the low-oxygen zone is back, thanks to the same "upwelling" conditions caused by current-driven winds that blow nutrient and oxygen-rich water off the continental shelf and replace it with hypoxic water from farther out to sea. In recent weeks, prevailing south winds had reversed early indications that a dead zone was on its way, because it's the summer's typical north winds that cause the upwelling. But the north wind returned about a week ago, bringing cool air to the coast and suffocating water closer to shore.

In the next few weeks, scientists will be able to determine just how bad things are going to get. If the north wind continues to blow, it's bad news for nearshore ocean life. Last year's summer winds were more intense than normal, for example, and the resulting upwelling was twice as strong.

Last year's low-oxygen levels were "off the charts and they continued through the end of October," Chan said. "We have seen nothing to suggest that conditions this summer will be any different."

Winston Ross can be reached at [phone] or rgcoast@ oregonfast.net.