Dead Zone Pollutant Grows Despite Decades of Work

Image: NASA Science Earth

HERMANN, Mo. ? The Missouri River stretches more than a quarter-mile from shore to shore here, its muddy water the color of coffee with a shot of cream.

The river carved this valley hundreds of thousands of years ago, and in the 1830s, it deposited the German settlers who founded this city. Today, visitors who sip local wine in hillside gazebos can gaze down at the water and imagine being on the Rhine.

For two centuries, Hermann has been known for the Missouri River ? and now the river is making Hermann known for an unexpected reason: It is a hot spot for nitrate.

Washing off farms and yards, nitrate is largely responsible for the Gulf of Mexico?s infamous ?dead zone.? Nitrate and other nutrients from the vast Mississippi River basin funnel into the Gulf, sucking oxygen out of the water and killing almost everything in their path.

The pollution is one of America?s most widespread, costly and challenging environmental problems, according to the U.S. Environmental Protection Agency.? Sewage treatment plants along the rivers already have spent billions of dollars, and some farmers now use computers to apply fertilizer with pinpoint precision.

But after three decades of extensive efforts to clean it up, nitrate along the rivers is getting worse. In Hermann, the levels in the Missouri River have increased 75 percent since 1980, according to U.S. Geological Survey research published last year.

The pollutant continues to pour into the rivers, and ultimately the Gulf, at a growing pace. And no one ? at least yet ? has figured out exactly why.

1,247 miles downstream
Hermann is an ideal place to start unraveling the mystery. There are no big factories here, no major sewage treatment plants, and not even much of the intensive row-crop agriculture sometimes blamed for heavy runoff. Rather, this small city looks like something out of a German fairy tale. Churches, shops and red-brick houses line tidy streets. Vineyards dot the rolling hills. Tourists arrive via Amtrak train to hear oom-pah bands at Oktoberfest and dine on bratwurst with sauerkraut.

How could Hermann be responsible for increasing the pollution that creates a dead zone 1,247 miles downstream?

The answer is Hermann is merely a microcosm of an immense problem involving 31 states and more than 76 million people.

Hermann sits roughly in the center of the vast Mississippi River basin, which drains 1.24 million square miles stretching from the Rockies to the Appalachians.

The Missouri River, as it rushes past Hermann?s churches and shops, carries the residue of life upstream. Rain washes excess nitrogen and phosphorus, along with other pollutants, from farmers? fields, cities, factories, cars and suburban lawns into ditches, streams and tributaries, and finally to the river itself. The ?Big Muddy? joins the mighty Mississippi just north of St. Louis, then makes a sharp right turn and rushes past the soaring St. Louis Arch on its way to the sea off Louisiana.

When the nutrient-rich water empties into the Gulf far downstream, it triggers a biological phenomenon with deadly results. The nutrients serve as an all-you-can-eat buffet for hungry algae. The phytoplankton population booms and then dies, sinking to the bottom, where bacteria decompose the organisms and use up precious oxygen in the process. The resulting low-oxygen environment ? also called hypoxia ? is so toxic that all animals must flee or die.?

Hypoxia drives away shrimp, crabs and fish and kills creatures such as worms at the bottom of food chains.

?There is die-off, a loss of ecosystem diversity,? said Nancy Rabalais, a marine ecologist and director of the Louisiana Universities Marine Consortium in Chauvin, La. ?If you have continuous year-after-year hypoxia, some animals won?t be able to recruit back into the area.?

Source: http://rss.sciam.com/click.phdo?i=19848cc57ac27579ad97dbd26ca237de

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