A River Runs through It: Everyone Agrees That the Only Way to Fix the Gulf of Mexico Dead Zone-The Largest off the United States-Is to Fix the Mississippi, but Not Everyone Agrees How

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To get an idea of how American coastal waters might look just before they succumb to all the degradations they have suffered these past five centuries, it would be worth taking a July trip to Mobile Bay, an Alabama inlet that feeds into the Gulf of Mexico. If the air is still and hot, an event may occur that Gulf Coast residents call a 'jubilee." The bottom-dwelling flounder will be among its first victims, growing agitated as each successive gulp of water brings less and less oxygen across their gills. In a panic, the fish will head shoreward toward the only breathable water they can find--the tiny oxygenated riffle the sea makes as it bumps lazily against the beach. At the shoreline, they will find humans waiting for them armed with "gigs," crude sticks with nails protruding. With an easy stab, each gigger will impale a suffocating fish, sometimes two at a time. Wading out farther, the fishermen will find sluggish pods of blue crab and brown shrimp. As the bay slowly asphyxiates and the free-for-all reaches its climax, the human whoops coming from the darkness will give the impression of a happy time--a celebration of the ocean's seemingly endless gifts.

But make no mistake. The Mobile Bay jubilee, while generally accepted as a naturally occurring phenomenon, is no cause for celebration. It is, in fact, a harbinger of a much larger unnatural jubilee occurring next door in the Gulf of Mexico. At least since the 1970s, an oxygen-depleted "dead zone," orders of magnitude larger than the Mobile event, has been forming and growing in the Gulf to the point where it now averages 5,700 square miles, bigger than the state of Connecticut. Nancy Rabalais, the executive director of the Louisiana Universities Marine Consortium and the dead zone's leading researcher, likens the phenomenon to the equivalent of "stretching a sheet of plastic wrap from the mouth of the Mississippi River west to Galveston, Texas, and sucking out all the air."

That this suffocation is taking place atop one of the most important commercial fishing grounds off the United States is alarming. Yet, as environmental issues go, the Gulf dead zone, indeed all dead zones around the world, remains persistently below the public's perception. Unlike strip-mining or deforestation, the Gulf dead zone is hard to observe. It forms miles from shore in an area only fishermen and oil prospectors frequent. And unlike other ocean problems, such as overfishing and offshore oil drilling, no immediate culprit can be identified at the scene of the crime.

But the more one examines dead zones (or "eutrophication-induced hypoxic areas," as they are scientifically termed), the more one comes to understand they are critical to the future relationship between land and sea. Yes, dead zones are only now becoming a serious global problem. As they spread and worsen, they begin to reveal a terrible truth: That around the world humans are sacrificing seafood for land food.

Let me explain: Dead zones begin when rivers carry nitrogen and phosphorus-based nutrients--primarily agricultural fertilizers--into the ocean. In the case of the Gulf of Mexico, it is the Mississippi River that delivers nitrates, nitrites, and phosphates from the American heartland into the Gulf at a rate of 1.7 million tons per year. Once this stew of nutrients reaches the ocean, algae bloom in prodigious amounts. When those algae die and settle to the bottom, bacteria consume them, sucking life-giving oxygen from the water. Compounding the problem: The freshwater that brings in these nutrients is less dense than the hypoxic saltwater and acts as something of a lid on the crypt below.

As industrial agriculture and animal feedlots have spread around the globe, dead zones have been spreading exponentially along with them. According to a 2008 study published in the journal Science, dead zones now affect 95,000 square miles of water in 400 different systems. They can be as small as the one in Mobile Bay or as large as the nearshore of Europe's Black Sea. …