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Efforts to shrink Gulf’s ‘dead zone’ face serious setbacks from oil spill

A satellite image shows cleanup vessels near the oil slick in the Gulf of Mexico.
A satellite image shows cleanup vessels near the oil slick in the Gulf of Mexico.

The massive environmental disaster unfolding in the Gulf of Mexico — oil gushing uncontrolled from a damaged well — threatens to compound a different problem that originates 1,200 miles north of the Gulf in Minnesota.

The Gulf’s so-called dead zone, caused by nitrogen runoff along the banks of the Mississippi River, already was suffocating oysters, clams and other sea creatures during the summer months.

Now, the growing oil slick could exacerbate that problem by further depleting oxygen that is vital to a myriad of marine life forms, said John Gulliver, a civil and environmental engineer who conducts research at the University of Minnesota’s St. Anthony Falls Laboratory in Minneapolis.

Timing will be a key. And time does not appear to be on the side of those working to avert the union of the two man-made assaults on life in the Gulf’s waters.

An explosion at the Deepwater Horizon floating rig on April 20 killed 11 workers, and damaged pipes are bleeding more than 200,000 gallons of oil a day into the Gulf’s waters.

It will be at least a week and possibly as long as three months before the well’s spurting oil deep below the Gulf’s surface is contained, Tony Hayward, chief executive of the oil giant BP, said Monday on NBC’s Today Show. The difference depends on whether temporary fixes work in the short term to stem the flow until BP can drill a relief well to control the oil on the Gulf’s floor. 

Hayward’s worst-case-scenario — that it would take up to three months to control the gusher — could extend this crisis into summer, when it would compound the effects of the dead zone.

Flowing from the heartland
In the Gulf’s dead zone, oxygen is severely depleted during warm summer months, literally suffocating life in an area roughly the size of Massachusetts.

The problem originates in Minnesota where the Mississippi River begins to drain the nation’s agricultural heartland. The river picks up nitrogen and phosphorus used to fertilize fields — and urban lawns too. Concentrations of the chemicals grow as the river flows past Iowa, Illinois and points south.

Once the chemicals reach the Gulf, they stimulate an unnatural super bloom of algae. The algae die and sink to the bottom where bacteria decompose them. And the bacteria suck up oxygen, leaving the water in a state known as hypoxia — which means there is inadequate oxygen to support living cells.

How Stuff Works offers a video of the process here.

Other subtle factors contribute to the oxygen depletion, such as the layering of fresh and salt water as the Mississippi enters the Gulf.

There is nothing subtle about the results: Lobsters, oysters and other slow-moving creatures are trapped and die. Even fish that flee for their lives suffer side effects such as shrunken reproductive organs and problems in spawning.

Fire boat response crews battled the blazing remnants of the off shore oil rig Deepwater Horizon in this photo taken on April 21.
REUTERS/U.S. Coast Guard
Fire boat response crews battled the blazing remnants of the off shore oil rig Deepwater Horizon in this photo taken on April 21.

Years before the explosion on the Deepwater Horizon rig, the dead zone was pitting the Gulf’s $2.8 billion a year fishing industry against the economic and political interests of mighty agriculture in the Upper Midwest.

A serious setback 
Minnesota organizations from the Department of Natural Resources to the Science Museum of Minnesota have contributed over the years to efforts to coax northerners along the Mississippi to take responsibility for their own runoff. They called upon farmers, in particular, to pitch into efforts to shrink the dead zone.

In 2008, a consortium of government agencies called the Mississippi River Gulf of Mexico Watershed Nutrient Task Force set out goals for significantly reducing the zone. Its average size over the past five years was 6,000 square miles. The interagency task force proposed to shrink it to 2,000 square miles by 2015.

Last year, the zone was smaller than expected. But it was more severe, extending closer to the surface than in previous years, according to the National Oceanic and Atmospheric Administration.

Now the efforts to shrink it face a serious setback.

Oil gushing into the Gulf could further starve the water for oxygen, said Gulliver, the environmental engineer in Minneapolis.

John Gulliver
John Gulliver

Oil is a source of carbon, which, like nitrogen, can give rise to more oxygen-using organisms in the water. The carbon effect may not be as significant, but it would add to a problem that already is lethal for sea life in the Gulf, Gulliver said.

Further, the oil slick on the Gulf’s surface can slow down the process by which oxygen is transferred from the atmosphere to the water, he said.

The upshot is that the beleaguered Gulf region faces a double whammy of disasters this summer. The dead zone diminishes in winter because the algae need warm temperatures and ample sunshine to flourish, Gulliver said.

“So the timing may not be right now,” he said. But the danger mounts as the days wear on.

Lucky on land but not at sea
Gulf coast residents counted themselves lucky Monday as winds drove the swelling oil slick away from shore, sparing the contamination of beaches, shipping ports and fragile coastal marshes.

Not so lucky were sea creatures, from endangered turtles to schools of newly hatched fish, that are caught in the slick estimated by Reuters to measure at least 130 miles by 70 miles.

Even if the well is brought under control next week, the critical question for life at sea is how long it will take to clean up the millions of gallons of crude oil that already are in the water.

There is reason to hope for relief there too, the New York Times said today: “Engineers said the type of oil pouring out is lighter than the heavy crude spilled by the Exxon Valdez (accident in Alaska in 1989), evaporates more quickly and is easier to burn.”

The oil in the Gulf “also appears to respond to the use of dispersants, which break up globs of oil and help them sink,” the Times said.

Still, the oil is “capable of significant damage, particularly when it is churned up with water and forms a sort of mousse that floats and can travel long distances,” it said.

Come mid-summer, what’s left of that slick is almost sure to overlap with the dead zone — which can shift to and fro in the Gulf, Gulliver said.

No one knows the full measure of the damage such a grim union could cause. When it comes to environmental problems, one plus one doesn’t always add up to two. The sum can be much larger as combinations of factors give rise to new problems.

Taking samples near the spill
Meanwhile, NOAA closed more than 6,800 square miles of federal fishing areas, from the mouth of the Mississippi to Florida’s Pensacola Bay, the Associated Press reported on Monday.

NOAA Administrator Jane Lubchenco says government scientists are taking samples from the waters near the spill to determine whether there is any danger.

State and local agencies joined the effort to measure the full toll so far on marine life.

“None of us have ever had experience at this level before,” Bob Love, coastal and nongame resources administrator with the Louisiana Department of Wildlife and Fisheries told the AP. “The longer it goes, the more fish and wildlife impacts there will be.”

Sharon Schmickle covers science, international affairs and other subjects for MinnPost.

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Comments (5)

  1. Submitted by Sheila Ehrich on 05/04/2010 - 01:17 pm.


    I have always respected your science writing. First of all you are very knowledgeable, and secondly you search out a vast array of expert sources to go to to fill in the specifics that may not be a part of your knowledge base. Lastly, you write very clearly, explaining what the average reader may not understand in language that is understandable and not that of a Ph.D. scientist or jargon.

    However, the one thing I have never been able to understand is how on one had you can shill for the very corporations, i.e. Cargill, Monsanto, Pioneer, etc., that make corporate farming a requirement if you want to make money and therefore make the use of nitrogen and phosphorus fertilizers seemingly mandetory, and on the other hand criticize farmers by saying, “the dead zone (is) pitting the Gulf’s $2.8 billion a year fishing industry against the economic and political interests of mighty agriculture in the Upper Midwest” and, “(The DNR and others have) called upon farmers, in particular, to pitch into efforts to shrink the dead zone”

    (Yes, I recognized that Cargill, et al are part of the “economic and political interests of mighty agriculture”, but I’m not sure that a sizeable number of your average non-farm citizens would understand that unless it was spelled out for them. “Ag” seems to equate with “Farmers”)

    As someone who was formerly an SWCD Supervisor for Faribault County and on a number of committees which were trying, back in the ’90s, to clean up the Minnesota River as well as the Blue Earth River Basin, I know there are farmers who would be willing to reduce their inputs. For one thing they are a huge part of the expense side of growing crops. But they don’t feel they have an option if they want to continue to produce the number of bushels necessary to make a profit as well as make a living.

    Furthermore, the ups and downs of CREP (Conservation Reserve Enhancement Program) have pretty much made it impossible for farmers to set aside those acres that would assist them in mitigating fertilizer runoff.

    You need to includes some of the farmers’ side of the story in what you report when you report on a topic such as the Dead Zone.

    Also, Minnesota recently passed a law banning phosphorous in lawn fertilizers. Is anyone getting numbers on how this has reduced Minnesota’s phosphorous input into the Mississippi? Have other states along the Mississippi done the same? This would add a bigger picture to your story.

  2. Submitted by Nathan Blumenthal on 05/04/2010 - 01:30 pm.

    Excellent article but I’m wondering what all this means in combination with the dispersants that are being used to ‘dispose’ of the oil. There’s a pretty scary article @

    It would be great if you could find out what the all chemicals in the dispersants are. One has to wonder; will it be safe to eat seafood from that region (provided of course that there’s anything left alive)?

  3. Submitted by rolf westgard on 05/04/2010 - 01:55 pm.

    Thank you, Sharon, for explaining that we had a serious hypoxia issue in the Mississippi Delta region long before the current oil spill. That issues results in part from ignorant legislatures passing biofuel mandates and subsidies with the encouragement of agribusiness. We now devote 30 million prime crop acres to produce the corn which makes the moonshine we put in our gasoline tanks. This requires a lot of nitrogen based fertilizer and conversion of conservation lands.

    We wring our hands over the issue, but rebel at the idea of a substantial gasoline tax and funds for major public transport. If we are looking for someone to blame for those agri-based dead zones, we can simply look in the mirror.

  4. Submitted by Richard Schulze on 05/04/2010 - 07:38 pm.

    As I read all the environmental criticism of this spill (and don’t get me wrong, much of it is deserved), I am struck by what I see around me: folks are reading this online, powered by electricity most likely from a fossil-fuel plant, sitting on plastic, eating and drinking from plastic (or Styrofoam, or waxed paper cups), holding plastic bottles, listening to IPods, wearing synthetic fibers, and driving fossil-fuel vehicles. In this context, a lot of criticism rings hollow.

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