In Oregon, a close-up look into a coastal dead zone
OFF CAPE PERPETUA, ORE.
A half-dozen scientists huddle in a cramped lab aboard the research vessel Elakha, bracing themselves against the rolling swells. As they stare at a pair of TV monitors, images of an aquatic graveyard glide across the screens.
Some 150 feet below, a robotic submersible – looking more like a portable generator with thrusters than a svelte submarine – motors just above the bottom, capturing macabre images of Oregon's newly minted and poorly understood "dead zone."
The zone is a bottom-hugging layer of water with oxygen levels so low that it can't support the variety of marine life that typically lives in these near-shore coastal waters. The bottom is littered with dead crabs, worms, and starfish. White anemones, brilliant in the submersible's spotlights, look as if they are taking their last gasp. In two runs lasting roughly an hour each, not one fish – dead or alive – appears on screen.
Unlike the dead zone that sets up each year in the Gulf of Mexico, Oregon's version can't be traced to the effects of nutrient-laden river run-off. Here, as in a handful of other coastal regions worldwide, the culprit may be global warming.
To be sure, the jury is still out on that connection, says Jane Lubchenco, a marine zoologist at Oregon State University who is heading up this day-long expedition. But, she adds, what she and her colleagues see is consistent with projections of global warming's effects on coastal winds in the spring and summer, which drive upwelling of nutrient-laden water.
These effects – identified as early as 1990 by researcher Andrew Bakun, then with the National Oceanic and Atmospheric Administration's fisheries lab in Monterey, Calif. – turbocharge the upwelling. This overloads the waters with nutrients and spawns large algae blooms. The algae sink, die, and decompose, in a process that sucks oxygen out of the water and the topmost layer of sediment on the bottom, where many worms and shellfish live.
First discovered in 2002, Oregon's low-oxygen, or hypoxic, zone is longer, thicker, and more oxygen-deprived this year than at any time in the past four years. "This hypoxia is noteworthy because it's telling us that the ocean is changing," Dr. Lubchenco says. "We don't understand completely why or what it means. But we're listening; we're paying attention."
In the process, the investigation is raising so many questions about the near-shore ecosystems that it is exposing a gap in America's oceanographic research: essentially from a depth of 150 feet up to the tidal zones along the shore.
It's a region rich in biology and important physical processes. But much of it is too shallow for large research ships to explore, often too turbulent for regular research dives, and – as today's cruise shows – it's no picnic for scientists on smaller boats.
With a length of 54 feet and berths for four, the Elakha is modern, but she's essentially a day-cruiser.
Scientists aren't out long enough to find their sea legs. Everyone spends nine hours bending, leaning, and shifting weight to retain their balance.
"We'll sleep well tonight," quips Francis Chan, a biogeochemist at Oregon State who is gathering water samples from the bottom to monitor their oxygen content.
Scientists discovered the hypoxic zone during a project aimed at seeing what was living in the rocky offshore reefs just north of Florence, Ore., says Hal Weeks, a project leader in the Oregon Department of Fish and Wildlife's marine resources program. The area is remote, so it isn't heavily fished. This made it ideal for serving as a model of what a healthy Oregon reef community ought to look like.
Indeed, cruises in 2000 and 2001 with the department's robotic underwater videographer revealed a reef replete with sea anemones, star fish, sea cucumbers, as well as rock fish and other deep-water species.
A year later in 2002, following reports of deep-water fish showing up in tide pools, gathering in unusual numbers in shallow water, and dead crabs comprising up to 75 percent of a crab net's haul, scientists took another look.
"Sculpin on the bottom were belly-up; you could almost see the Xs in their eyes," Lubchenco recalls.
Even on this cruise, the scientists note a dramatic change between the images of two weeks ago and those from today – fewer live starfish, stressed anemones, and rocks covered with thick white mats of what could be new colonies of bacteria that thrive in low-oxygen environments. Water samples Dr. Chan took during this cruise show the water's oxygen content at record low levels compared with the past four years.
Not everyone is convinced that what Lubchenco's group sees portends long-term changes.
Barbara Hickey, a University of Washington oceanographer who is looking into hypoxic conditions off in Washington state, suggests that "it's very premature to say this is new or getting worse." It may look that way in the context of the past six years, she acknowledges, but looking at these conditions off Washington, they've appeared on and off before in oceanographic records from the 1960s and '70s. The same may hold true for Oregon, she suggests.
Still, she cautions, "if it is getting worse, then it could be very important."
Yet Lubchenco adds that she and a colleague have been studying the affected patch of Oregon's coast for some 30 years. Never before has she seen the shoreline evidence – deep-water fish in the intertidal zone or large numbers of dead crabs washed ashore – that people are finding today.
Several questions loom large. For one, the team isn't sure it's found the dead zone's full extent. They know it's moved farther north than in the past, but they haven't been able test the waters farther south than this day's cruise because it would take them beyond their vessel's one-day range.
If a severe hypoxic zone becomes an annual event, its effect on the coastal ecology could be profound. For example, it could prove an insurmountable barrier to larvae that currents carry along the coast to "seed" other near-shore habitats.
Meanwhile, researchers at the University of California at Berkeley and the National Center for Atmospheric Research in Boulder, Colo., are developing a sophisticated computer model that should be able to tease out whether global warming – or some type of natural atmospheric variability – is playing a role in the dead zone's formation.
It's pretty clear El Niño is not implicated, says Thomas Powell, a UC-Berkeley oceanographer. But, he continues, there may be other large-scale changes in average atmospheric conditions that typically occur every 30 years.
One such shift occurred in 1975 in the North Pacific "and it showed up in about 40 different indicators, which had an abrupt change about that time," he says. And it shows up in climate models.
It could be, he continues, that "basic circulation patterns in the North Pacific could have substantially changed, and it's just taken awhile for the system to react and settle down in this different state. I think that's been dismissed a little too early" in the hunt for causes of Oregon's dead zone "and more work needs to be done." The computer model to test these ideas should be ready for its first runs in about six months, he says.