Seastars feasting on Dungeness crabs that succumbed to low oxygen conditions during 2004. Dungeness crabs are not a normal part of the diet of tidepool seastars. (Photo: Jane Lubchenco)
There are about 200 oxygen depleted regions, or dead zones, in the world’s oceans. They occur when nutrients from run-off – fertilizers and manure to name a few – make it into major water bodies and cause oxygen depletion. But a dead zone off the coast of the Pacific Northwest has scientists looking at a different culprit – climate change. Host Steve Curwood turns to Professor Jack Barth of Oregon State University to learn more about what might be behind the Northwest dead zone.
CURWOOD: We like to picture the ocean as teeming with life – fish and crabs and strange glowing eels, that sort of thing. But in many parts of the world the ocean is dying. There are currently about 200 dead zones, almost all of them caused by fertilizer or sewage run-off. But one dead zone off the coast of the Pacific Northwest has been expanding over the past few years, for causes that are harder to fix. Joining me now is Professor Jack Barth of the College of Oceanic and Atmospheric Sciences at Oregon State University. Professor Barth, welcome to Living on Earth.
BARTH: Thank you, Steve.
CURWOOD: So the news is, the dead zone off of the Pacific Northwest might well be connected to climate change. How and why would that be?
BARTH: Well, we’ve seen low oxygen or hypoxia in these areas where there is significant green life die-off, so-called dead zones. We’ve seen that over the past five or six years, and we think that’s unusual on the backdrop of about a fifty year’s worth of data. So we’re looking towards the cause, and we think there’s a hint in the winds and how they’re changing and how that affects these dead zones.
BARTH: Well, this one’s unusual because it’s on an open coastline. It should be flushed regularly. There are no rivers putting nutrients in – that’s the cause of most of the hypoxia zones around the world. Well it’s all connected to the winds. The winds blow on the coast, they bring up these deepwaters from offshore, right in next to the coast. That fuels these phytoplankton blooms that then decompose and pull the oxygen out of the water. So we can go back to the winds, are the winds changing. And we know that with climate change there can be changes in the wind. Particularly they can increase in strength, so this whole scenario where we’re producing lots of plankton that can decompose, that might be worse as we go into a climate change scenario.
CURWOOD: Why isn’t this, you know, just something that’s cyclical, that every ten or twenty, or maybe every fifty years this happens, the way you get other oscillations in the ocean, like the whole El Niño/La Niña phenomenon?
BARTH: Yeah, we were quite interested in that. There’s a big ten year change out here in the Pacific, and when we first saw this we said, ah ha that’s just one of these ten year swings. But having gone back over that fifty year record, this recent five or six years really is unusual. So I can tell you that it’s not part of a decadal, or a ten year oscillation. Whether it’s fifty or a hundred years, we don’t know.
BARTH: Well, first thing you notice, there’s lots of something called marine snow, this white, flocky material coming down from the surface. That’s the plankton falling down that’s gonna be decomposed and lead to the hypoxia. Next thing you notice is there aren’t any fish in the area. So in all of our surveys in ’06, we did not see any fish in this zone. Then you notice the piles and piles of dungeonous crab carcasses on the sea floor. Amongst them are sea worms that have come out from the bottom and are just flapping in the currents. Some of these majestic anemones, white, about two feet tall, starting to slump over from lack of oxygen. There usually are lots of sea star species. We saw some of those actually collapsing from lack of oxygen – so basically this wholesale area of nothing alive and lots of death.
CURWOOD: Going over a couple of articles written about your research, there was a story of some fisherman having crabs kind of jumping out of the water there? What’s that all about?
BARTH: Yeah, what happens is those that can get away do. And what I saw myself is, my son and I go recreational crabbing, and we were in the bay near the dead zone and catching phenomenal sized crabs, sort of dinner plate sized in fifteen minutes or less. And those were the crabs that were running into shore, running into shallow water where there is oxygen. I’ve also heard reports of small octopi coming up the lines of the fisherman, trying to get out of that dead zone near the bottom of the water.
CURWOOD: And this isn’t happening just off the Pacific Northwest. This is elsewhere on the planet.
CURWOOD: So what an irony this is. The wind blows in too much food for the fish, and actually if people are in the area, the fish, in fleeing the dead zone as that too much food decays, also they get this huge bounty. So we’re getting this inverse signal from nature that a lot of nutrient and, over the short term, a lot of seafood.
BARTH: Yeah, that’s exactly right. If you think about this whole process as fueling a healthy ecosystem, there was a balance there and now somehow we’ve pushed that a little too far, and as these dead zones develop the creatures are fleeing to the edges looking for oxygen refuges and concentrating, and we’re really not sure what the ripple effect will be – will they be more subject to being preyed upon in those areas?
CURWOOD: Professor Jack Barth teaches at the College of Oceanic and Atmospheric Sciences at Oregon State University. Thanks so much, Jack.
BARTH: You’re welcome, Steve.
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