The Dead Zone

What It Is

It’s a dreadful name for a dreadful phenomenon caused by the pollution the Mississippi River carries into the Gulf of Mexico. The dead zone describes the area of the Gulf at the mouth of the Mississippi River whose waters can no longer support marine life because it is starved of oxygen. While the size of the dead zone changes seasonally, the floods of 2008 produced one of the largest dead zones yet. It covered more than 8,000 square miles—an area roughly comparable to the size of New Jersey or twice the surface area of all the inland lakes in Minnesota.

The River releases tens of thousands of pounds of fertilizer and animal manure, which are loaded with the nutrients nitrogen and phosphorus, into the Gulf. These nutrients "over-fertilize" the water, creating massive algal blooms that use up much of the dissolved oxygen in the water off the Louisiana and Texas coast.

Why It Is Important

No oxygen (or insufficient oxygen) means no life. The oxygen-depleted waters force fish and wildlife to migrate out of dead zones, while bottom–dwellers like Gulf shrimp often cannot escape the dead zones and die. Scientists call this oxygen-depleted condition hypoxia, and it is getting worse in the Gulf.

Reducing the amount of pollution, especially nitrates, that is carried into the Gulf via the Mississippi River is essential to restore healthy conditions in the Gulf and the river system. Agricultural pollution from the extensive Corn Belt is damaging the entire watershed. We can clean up and protect the River and shrink the dead zone by reducing chemical inputs on farms, shifting to more sustainable farming practices and improving "green infrastructure" to capture and filter runoff in wetlands, forested flood plains and other natural systems. Restoring natural floodplains, meanders and other features that slow the volume and intensity of floods will also help capture sediments and nutrients, reducing the tons that reach the Gulf.

What You Can Do

At home, River Citizens can help by conserving water, eliminating "cosmetic" uses of lawn and garden fertilizers, properly disposing of pet waste and supporting farmers who maximize their use of soil and nutrient conservation practices. For more information on what you can do, go to the  River Action Items section. To learn more about hypoxia and the Gulf of Mexico:

• Visit the Gulf of Mexico Dead Zone site, developed by the Science Museum of Minnesota, or
• Watch the HowStuffWorks video on hypoxia in the Gulf of Mexico.