The dead zone in the Gulf of Mexico, that area of lifeless water where the Mississippi River meets the ocean, has been growing steadily over the past two decades. According to the Louisiana Universities Marine Consortium, this portion of the Gulf could top out at over 8,500 square miles this summer, up from last summer's high of 6,662 square miles.
A dead zone is an area of water that is experiencing 'hypoxia,' or in other words, is completely devoid of oxygen and unable to sustain life. Also known as eutrophication, this phenomenon is caused by the decomposition of algae, which robs the surrounding waters of oxygen.
While this process is natural and would otherwise be a harmless part of aquatic ecosystem functions, the problem is exacerbated by ever-increasing levels of fertilizers that find their way to the Mississippi from watersheds as far north as the river's source in Minnesota, to its mouth in Louisiana. As the river flows from north to south, the concentration of nutrients increases until it spills out into the Gulf at record levels each year.
Agriculture is the leading source of nonpoint water pollution in the United States. (Nonpoint simply means the source is from a larger, harder to pinpoint area than, say, a factory that's near a body of water.) The increase in intensive commercial farming practices has brought the use of fertilizers containing phosphorus and nitrogen to a level that is sending algal blooms on a growth spurt, which has many extremely worried about the fate of marine life in the Gulf, not to mention the viability of the fishing industry. According to the United States Global Change Research Program, the amount of nitrogen delivered by the Mississippi River basin has tripled over the last four decades!
To make matters worse, recent studies suggest that global warming could be compounding the problem through a change in warm weather wind patterns that alter ocean circulation patterns.
The possible solutions, then, appear to be twofold.
1.) Increase CRP and riparian forest areas along streams in the Mississippi basin. Let's keep runoff from entering streams that feed into the river. Better yet, transition to organic farming practices that boost soil fertility with little supplemental fertilizer.
2.) Simultaneously with the first solution, continue to work toward climate change mitigation.