Toxic Substances Hydrology Program
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.
USGS Information on Hypoxia
More Information on Hypoxia
Information on Hypoxia in the Gulf of Mexico
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.