Home Archived July 28, 2016

National Wetlands Research Center

All USGS NWRC only

Restoring Life to the Dead Zone: Addressing Gulf Hypoxia, a National Problem

USGS Fact Sheet 016-00

Image if interior watersheds of the Mississippi River Basin
Interior watersheds of the Mississippi River Basin, the source of materials causing the 6,000- to 7,000-square-mile "dead zone," or hypoxia in the Gulf of Mexico.
June 2000

(PDF Version, 835 KB) (The PDF version of this document requires the latest version of Adobe Reader or similar software. Download the latest version of Adobe Reader, free of charge.)


The hypoxic zone in the Gulf of Mexico, the so-called "dead zone" lacking enough oxygen to support most marine life, is one of the largest environmental issues of the decade. Practical solutions, based on sound science, are needed.


The hypoxic zone is an area of approximately 6,000-7,000 square miles of water with oxygen levels below 2 parts per million. Trawlers are unable to catch any shrimp or bottom-dwelling fish at this low level of oxygen, and dead organisms have been found there.


The zone occurs between the inner and mid-continental shelf of the northern Gulf of Mexico, from the Mississippi River birdfoot delta westward, to the upper Texas coast.


There has been awareness of the problem since the 1970's, but scientists are unsure whether or not this is a recent problem that has been worsened by nutrient application.


The zone is caused by increased nutrients from the Mississippi River, especially nitrogen and phosphorus from fertilizers, animal wastes, and domestic sewage; seasonal river discharges worsen the nutrient enrichment. Average nitrate-nitrogen concentration in the river's mainstem has doubled since 1950, with commercial fertilizers being the largest source. Nutrients encourage algal blooms, alter the food chain, and eventually deplete the area of oxygen.

Image of distribution of water hypoxia
Distribution of water hypoxia from July 21-25, 1998. Data from Hypoxia Monitoring Studies of N.N. Rabalais, R.E. Turner, and W.J. Wiseman, Jr.


The Gulf's hypoxic zone rivals the largest hypoxic areas in the world such as those in the Baltic Sea and Black Sea. Change in distribution of shrimp and fish pose a potential threat to the Gulf of Mexico's $4 billion a year seafood economy. Furthermore, though the Gulf bears the effects of the nutrients, the source of the nutrients is a national problem, involving the entire interior watersheds of the Mississippi River Basin and especially States from the Upper Mississippi Valley—Minnesota, Wisconsin, Iowa, Illinois, and Missouri—and the lower Mississippi Valley—Tennessee, Arkansas, Mississippi, and Louisiana.


The FY1999 Department of the Interior budget for USGS contains a request for the National Wetlands Research Center to conduct a $200,000 pilot project to demonstrate how to use wetlands to reduce nutrients.

Image of shrimper

Attacking the Problem


About 25% of the nitrogen load in the Mississippi River originates in the Lower Mississippi River Valley, downstream of the Mississippi-Ohio River confluence. While most work related to the hypoxia issue involves either nitrogen reduction in the upper reaches of the Mississippi Basin or in understanding the relation of nutrient loading and the hypoxia zone offshore, the USGS National Wetlands Research Center has chosen to take another approach—using inland and coastal wetlands to attack the hypoxia problem.

Image of crabResearch Activities

With NAWQA researchers, Center scientists will

  • Assess the role of coastal and inland wetlands in reducing nutrients that are transported into coastal waters.
  • Develop a model of interactions between wetland and other habitats and water quality.


Image of shrimping boatInformation from the research is particularly needed by the U.S. Fish and Wildlife Service, National Oceanic and Atmospheric Administration's National Marine Fisheries Service, National Park Service, U.S. Environmental Protection Agency, U.S. Department of Agriculture's Natural Resources Conservation Service, and the States of Arkansas, Texas, Louisiana, and Mississippi.


With additional funding, the Center can

  • Assess the impacts of nutrient enrichment on wetland and estuarine-dependent biological resources, in cooperation with the States of Mississippi, Texas, and Louisiana, the National Marine Fisheries Service, and the U.S. Fish and Wildlife Service.
  • Assess the effects of agricultural Best Management Practices in reducing nutrient inflows at the watershed level in the Lower Mississippi River Valley.
For more information, contact:

U.S. Geological Survey
National Wetlands Research Center
700 Cajun Blvd.
Lafayette, LA 70506

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.nwrc.usgs.gov/factshts/016-00/016-00.htm
Web Site Technical Issues: nwrcweb@usgs.gov
Web Site Content Questions: nwrcinfo@usgs.gov
Page Last Modified: Monday, 28-Sep-2015 14:01:57 EDT