CONTINENTAL CREEP: Hypoxic seawater from the deep ocean is moving into shallower near-shore environments off the Oregon coast, threatening or killing marine species that make their home there.
Image: iStockphoto
-
The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
Read More »
A plague of oxygen-deprived waters from the deep ocean is creeping up over the continental shelves off the Pacific Northwest and forcing marine species there to relocate or die. Since 2002 tongues of hypoxic, or low-oxygen, waters from deeper areas offshore have slipped into shallower near-shore environments off the Oregon coast, although not close enough to be oxygenated by the waves. The problem stems from oxygen reduction in deep water, a phenomenon that some scientists are observing in oceans worldwide, and that may be related to climate change.
The hypoxic seawater is distinct from the well-known "dead zones" that form at the mouths of the Mississippi and other rivers around the world. Those areas result from agricultural runoff, which lead to algae blooms that consume oxygen. Rather, the Pacific Northwest problem is broader and more mysterious.
Shelf waters off the Pacific Northwest extend anywhere from 30 to 80 kilometers offshore and lie beneath the California Current, one of the richest marine ecosystems in the world. Francis Chan, a senior research professor at Oregon State University, has been monitoring the area's low-oxygen events, which normally peak in the late summer months. "Oxygen is just about the most crucial necessity for anything biological," he says.*
Chan is one of a number of scientists alarmed at the dramatically reduced oxygen levels showing up in these waters. In fact, the Oregon Department of Fish and Wildlife put submersible vehicles off Oregon's coast during a hypoxic event that went anoxic (oxygenless) in 2006, he says, monitoring conditions and recording numerous carcasses of sea stars, sea cucumbers, marine worms and fish.**
Lothar Stramma, a physical oceanographer at the Christian Albrechts University of Kiel in Germany and his associates describe the hypoxic problem as global in a paper accepted for publication in Deep-Sea Research , stating that tropical low-oxygen zones have expanded horizontally and vertically around the world, and that subsurface oxygen has decreased adjacent to most continental shelves. Low-oxygen zones where large ocean species cannot live have increased by close to 5.2 million square kilometers since the 1960s, the team found. Where this expansion intersects with the coastal shelf, oxygen-deprived waters are slipping up and over shelf floors, killing off creatures such as crabs, mussels and scallops. Such bottom-dwellers normally have a lot to eat in such rich ecosystems, but these species are sensitive to oxygen loss. Similarly, the anoxic ocean at the end of the Permian period (around 250 million years ago) was associated with elevated carbon dioxide and massive terrestrial and oceanic extinctions.
Lisa Levin of the Scripps Institution of Oceanography in La Jolla, Calif., says that as oxygen-starved layers move upward, large animals such as marlin, tuna and sailfish will be forced into ever-shallower waters. "That may be good for fishermen, but it also makes it a lot easier for fishermen to fish these species out of the ocean," says Levin, who worked with Stramma on Deep-Sea Research .
Biodiversity will be the big loser as these low-oxygen zones knock out some species and promote others. Among the big winners is the Humboldt squid, which can tolerate low oxygen; it has expanded its range in the northeastern Pacific in the past 10 years, from the Gulf of California all the way to southeastern Alaska. Biologists worry about the hunting pressure the squid will put on other species.
Increases in jellyfish blooms also are likely to be part of the process. Levin encountered such blooms recently in low-oxygen environments off India's coast, where "the jellyfish were as thick as soup," she says. Larval fish are especially susceptible to low-oxygen ocean zones. "Larvae are really a ball of cells with a mouth and a gut. There is only so much they can do. They're not as mobile as fish," she says. Reproducing female crustaceans and fish may be adversely affected, as well.
Levin says that the Pacific's deeper currents keep its waters less oxygenated than those of the Atlantic. "It's what we call 'old water,' since deeper Pacific waters haven't been at the surface in a long time," Levin says. Stramma thinks that some of the Pacific's oxygen problems could also result from El Niño. But climate models predict reductions in dissolved oxygen in all oceans as average global air and sea temperatures rise, and this may be the main driver of what is happening there, she says.
Chan says that lighter warm water creates a cap over the colder depths, making it less likely that deeper waters—where everything from "plankton to whale poop" sucks up oxygen—will rise to mix with the oxygenated surface. Plus, warmer water simply holds less oxygen. According to Chan, most hypoxia-intolerant species engulfed in low-oxygen waters quickly move away. "But for those whose stress response is to hunker down and wait," he adds, "they will die."
*Erratum (2/24/10): This sentence was changed after publication. It originally stated that Francis Chan is a professor at the University of Oregon.
**Erratum (2/24/10): This sentence was changed after publication. It originally stated that NOAA put submersibles off the Oregon coast; it was completely rewritten both to correct the error and for clarity.
See what we're tweeting about
14 Comments
Add CommentThis might sound a bit naive, but if we wanted to do something about this, couldn't we extend an air pipe into the depths and simply pump air into the deep water? I don't know how much energy this would take, but it seems that the oxygenation potential would be large.
Reply | Report Abuse | Link to thisIs this just another bit of BS perpetrated by the discredited Global Warming gang?
Reply | Report Abuse | Link to this"Is this just another bit of BS perpetrated by the discredited Global Warming gang?"
Reply | Report Abuse | Link to thisHow would you be able to judge the difference between BS and non-BS, anyway?
Jürgen Hubert – Your unfortunate insult is actually a superb question. There is so now much information available to anyone, but so much of it is riddled with BS. Is there any source of information that is unimpeachable? Regardless of anyone’s intellectual acumen of subject area expertise, who can really tell?
Reply | Report Abuse | Link to thisdennyduffell – A couple of general observations: the atmosphere is mostly nitrogen, and any enrichment of oceanic oxygen levels would require depletion of atmospheric oxygen. I can’t do the math, but this sounds like a bad formula.
Reply | Report Abuse | Link to thisI’ve been wondering: to the extent that humanity’s oxidation of carbon fuels has increased atmospheric (and/or oceanic) CO2, there should be a commensurate depletion of oxygen. Perhaps an exchange of oceanic oxygen has maintained atmospheric oxygen levels. Unfortunately, there are no simple answers that would allow us to control extremely complex global systems, even if we did know what we’re doing.
Its a valid question, but the answer is you look to people's credentials and their past history. I tend to believe someone who's well educated in a field and does research in that field vs some random guy on the Internet who doesn't apparently want to hear what he doesn't want to hear. Its not always that easy, but if you consider that science clearly WORKS its evident that on the whole credentials mean something, and peer review means something, etc.
Reply | Report Abuse | Link to thistharter - Yours is the most reliable method of assessment. Thanks
Reply | Report Abuse | Link to thisdennyduffel is closer to a potential solution than most realize. I envision a fleet of flying electric generators (see skywindpower for how those are configured) exploiting the boundless and consistent energy available in high altitude winds. Excess electricity is used for hydrolysis, the resulting Hydrogen cryogenically stored for fuel, and the oxygen pumped to hypoxic depths. Scandinavian researchers are already investigating methods to do that effectively. Bubbles just come back up, and perhaps the best approach is to oxygenate water at the surface and pump that down. Eventually, the excess electricity high altitude winds provide could be used to take carbon dioxide and synthesize butane, methane, octane even, and pump that back into the ground in depleted oil fields, thus working on the Carbon Dioxide problem as well . . .
Reply | Report Abuse | Link to thisIncidentally, and adding to the above comment, this problem of hypoxic bottom waters is not limited to the oceans, but is appearing in major lakes as well. Lake Biwa in Japan is the source of water for 14 million people, who are responsible for a couple of percentage points of GWP, and similar dead zones have been documented by Dr. Michio Kumagai and associates in this lake. A decrease in vertical mixing in winter, when surface oxygen-rich waters do not chill enough to descend and thus bring up the deep low-oxygen water below. It is a phenomenom not limited to Lake Biwa . . . Any data on the Great Lakes, or, say, Lake Constance (5 million people) in Europe?
Reply | Report Abuse | Link to thisIncidentally, and adding to the above comment, this problem of hypoxic bottom waters is not limited to the oceans, but is appearing in major lakes as well. Lake Biwa in Japan is the source of water for 14 million people, who are responsible for a couple of percentage points of GWP, and similar dead zones have been documented by Dr. Michio Kumagai and associates in this lake. A decrease in vertical mixing in winter, when surface oxygen-rich waters do not chill enough to descend and thus bring up the deep low-oxygen water below. It is a phenomenom not limited to Lake Biwa . . . Any data on the Great Lakes, or, say, Lake Constance (5 million people) in Europe?
Reply | Report Abuse | Link to thisbrevan - Unfortunately, there are no simple answers that would allow us to control extremely complex global systems, even if we did know what we’re doing. The energy that has already been removed from the system cannot be predictably restored.
Reply | Report Abuse | Link to thisI suspect the most challenging aspect of your vision, believe it or not, would be to produce a reliable fleet of flying electric generators of sufficient capacity to reoxygenate the oceans. While the concept may even be technically demonstrable at small scales, I envision a fleet of flying turbines crashing to the surface in extreme weather.
No one has said that the flying electric generators would have to stay aloft in extreme weather. That's what the hydrogen harvested from the electrolysis is for: back-up thermal power plants whose waste product would be water (incidentally ideal for arid places like the Middle East, California and some people's imaginations). Nor would the FEGs (flying Electric Generators) have to be the entire answer to the Oxygenation problem. It should be enough that they enable us to shift away from fossil fuels. The oxygen byproduct is a bonus, as would be the use of low voltage currents to stimulate new growth in coral reefs, for example.
Reply | Report Abuse | Link to thisbrevan – Fine, fine. If you believe that you can provide a solution to reengineer the global environment, I certainly won’t stop you. It’s only taken 150 years for us and, to some undetermined extent, natural processes, to unintentionally affect the current global environment, with all our activities. Good luck with that.
Reply | Report Abuse | Link to thisend-Permian mass extinction... anyone?
Reply | Report Abuse | Link to this