Gulf of Mexico
The Gulf of Mexico is the ninth largest body of water in the world, and the Northern Gulf of Mexico is bordered by five U.S. states. The Mississippi River captures runoff from 41 percent of the land area of the contiguous United States (parts or all of 31 states) and flows to the Gulf of Mexico. Human activities have greatly altered the Mississippi River and its watershed. As a result, substantial amounts of sediment, nitrogen, phosphorus, and chemical pollutants are delivered annually to the Gulf of Mexico.
USGS estimates that agricultural sources contribute greater than 70 percent of the nitrogen and phosphorus delivered to the Gulf of Mexico from the United States. In contrast, urban sources account for approximately 9 to 12 percent. These findings illustrate how significant agricultural lands are as sources compared to urban areas in the Mississippi River Basin.
Nitrogen and phosphorus inputs that far exceed pre-industrial levels have resulted in the seasonal growth of large amounts of algae, which eventually die, sink to the bottom, and are decomposed. During this decomposition process, life-giving oxygen is depleted from bottom waters, thereby causing a "hypoxic zone" in the Northern Gulf of Mexico. This hypoxic zone causes serious problems for aquatic organisms, and thus threatens the economic and ecological health of one of the nation’s largest and most productive fin and shell fisheries. For more information about hypoxia and the effects of nitrogen and phosphorus pollution, visit Hypoxia, Anoxia & Harmful Algal Blooms and Effects of Nitrogen and Phosphorus Pollution.
The 2008 Gulf Hypoxia Action Plan, released by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, continues to be implemented. The Action Plan describes a national strategy to improve water quality in the Mississippi River Basin and to reduce, mitigate, and control hypoxia in the Northern Gulf of Mexico. Learn more about the 2008 Action Plan.
- Alexander, R.B., R.A. Smith, G.E. Schwarz, E.W. Boyer, J.V. Nolan, and J.W. Brakebill. 2009. "Differences in Phosphorus and Nitrogen Delivery to the Gulf of Mexico from the Mississippi River Basin" U.S. Geological Survey. Accessed October 2010.
- Gulf of Mexico Alliance. 2009. "The Gulf of Mexico Ecosystem, Watershed, and Economy." Northern Gulf Institute. Accessed October 2010.
- Mississippi River/Gulf of Mexico Watershed Nutrient Task Force. "2008 Action Plan." U.S. Environmental Protection Agency. Accessed October 2010.
- NOAA. 2000. "Hypoxia in the Gulf of Mexico: Progress Towards the Completion of an Integrated Assessment." National Oceanic and Atmospheric Administration. Accessed October 2010.
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