Agricultural Runoff in the Mississippi River Basin and The Dead Zone
Overuse and improper filtration of fertilizer in agricultural areas within the Mississippi River basin is causing hypoxia in Gulf of Mexico south of the Mississippi River delta. Excess levels of nitrogen and phosphorus cause heavy algal blooms. When these microorganisms decompose, oxygen is depleted from the water negatively impacts sea life off the coast of Louisiana. This dead zone has doubled in size over the last twenty years and has harmed the commercial shellfish and shrimping industry in the areas.
In addition to overuse of fertilizers, the destruction of the Louisiana wetlands reduces the amount of pollutants filtered before the Mississippi River discharges into the Gulf of Mexico.
Recently the Department of Agriculture has begun a program to award farmers who reduce the amount of runoff. Farmers are now using methods such as on site runoff detention and wetland filtration in order to reduce the impact of fertilizers on water quality.
Sources:
http://www.lacoast.gov/WATERMARKS/2004-09/5deadzone/index.htm