Hypoxia

Definitions

Hypoxia – “Hypoxia occurs … when oxygen concentrations fall below the level necessary to sustain most animal life. Hypoxia results when oxygen consumption, primarily through decomposing organic material, exceeds oxygen production through photosynthesis and replenishment from the atmosphere.” - Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, 2004

Hypoxia – "Hypoxia is the condition in which dissolved oxygen is below the level necessary to sustain most animal life- generally defined by dissolved oxygen levels below 2mg/l [miligrams/liter] (or ppm [parts per million]).” - Committee on Environment and Natural Resources, 2000

Hypoxia – “Hypoxia means low oxygen and is primarily a problem for estuaries and coastal waters. Hypoxic waters have dissolved oxygen concentrations of less than 2-3 ppm. Hypoxia can be caused by a variety of factors, including excess nutrients, primarily nitrogen and phosphorus, and waterbody stratification due to saline or temperature gradients. These excess nutrients, eutrophication, promote algal growth. As dead algae decompose, oxygen is consumed in the process, resulting in low levels of oxygen in the water.” - Mississippi River Basin Watershed Nutrient Task Force, 2010

Hypoxia – “A condition in which natural waters have a low concentration of dissolved oxygen (about 2 milligrams per liter compared with a normal level of 8 to 10 milligrams per liter). Most game and commercial species of fish avoid waters that are hypoxic.” - Stevenson and Wyman, 1991

Text in brackets (“[text]”) are additions by the editor.

Related Definitions

Nutrients

Eutrophication

Anoxic

Anaerobic

USGS Information on Hypoxia

• Hypoxia in the Gulf of Mexico
• Nutrients National Synthesis Project, National Water-Quality Assessment (NAWQA) Program
• Nutrient Enrichment and Criteria, NAWQA Program
• USGS CoreCast: Nutrient Sources and Gulf of Mexico Hypoxia
• USGS CoreCast: Too Much of a Good Thing--Increasing Nitrogen Deposition in Lakes
• Differences in Phosphorus and Nitrogen Delivery to the Gulf of Mexico from the Mississippi River Basin, NAWQA Program
• Restoring Life to the Dead Zone--Addressing Gulf Hypoxia, A National Problem: USGS Fact Sheet 016-00
• Search the Toxic Substances Hydrology Program's Bibliography for "hypoxia"

Related Headlines

• Nitrogen Isotope Study Answers Questions about the Transport of Nutrients in Streams
• New Report on Science for Hypoxia in Gulf of Mexico
• USGS Info Guides Gulf of Mexico Hypoxic Zone Action Plan
• USGS Leads a National Study on Hypoxia in the Gulf of Mexico, Flux and Sources of Nutrients in the Mississippi-Atchafalaya River Basin

More Information on Hypoxia

• Hypoxia Fact Sheet (pdf), Ecological Society of America
• Mississippi River Basin Challenges - Hypoxia, U.S. Environmental Protection Agency
• Oxygen Depletion in Coastal Waters, National Oceanic and Atmospheric Administration
• Harmful Algal Bloom Research and Control Act of 1998
• Eutrophication, Encyclopedia of Earth

Information on Hypoxia in the Gulf of Mexico

• Mississippi River/Gulf of Mexico Watershed Nutrient Task Force
• Science Assessment of the Causes and Consequences of Gulf of Mexico Hypoxia, National Ocean Service, National Oceanic and Atmospheric Administration
• Hypoxia Watch System for the Gulf of Mexico, National Oceanic and Atmospheric Administration
• Gulf of Mexico Ecosystems and Hypoxia Assessment, Center for Sponsored Coastal Ocean Research, National Oceanic and Atmospheric Administration
• Northern Gulf of Mexico Ecosystem Description, Hypoxia in the Gulf of Mexico (by Nancy N. Rabalais, Louisiana Universities Marine Consortium), National Oceanic and Atmospheric Administration
• Hypoxia In The Gulf Of Mexico and Nutrients in the Midwest, Illinois State Water Survey

References

Committee on Environment and Natural Resources, 2000, Integrated assesment of hypoxia in the Northern Gulf of Mexico: National Science and Technology Council, 58 p.

Mississippi River Basin Watershed Nutrient Task Force, 2010, Hypoxia 101: U.S. Environmental Protection Agency, access date May 28, 2010.

Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, 2004, A science strategy to support management decisions related to hypoxia in the Northern Gulf of Mexico and excess nutrients in the Mississippi River Basin: U.S. Geological Survey Circular 1270, 50 p.

Stevenson, L.H., and Wyman, B., 1991, Hypoxia, in Dictionary of Environmental Science: New York, New York, Facts on File, Inc., p. 125.

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