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Hypoxia and Eutrophication

Gulf of Mexico Hypoxic Zone
We research the relationship between nutrient pollution and ecosystem effects. The nutrient pollution from the Mississippi rivera fuels the Gulf of Mexico Hypoxic Zone. Image by NOAA's Environmental Visualization Lab.

Hypoxia occurs when the amount of dissolved oxygen in water becomes too low to support most aquatic life (typically below 2 mg/l). Hypoxic waters can become dead zones – animals that can escape do and those that cannot often die. Over the long term, animal populations and commercial and recreational shellfish and fisheries decline.

Every year, over half of the U.S. estuaries experience natural or human-induced hypoxic conditions at some time. Evidence suggests that the frequency and duration of hypoxic events is increasing. Although nutrient (i.e. nitrogen and phosphorus) discharges to estuaries from processes such as weathering of bedrock are natural, inputs from agricultural runoff, the burning of fossil fuels and waste water treatment discharges have increased inputs to many times natural levels. Recognizing the threat to America's coastal ecosystems and economies, Congress reauthorized the Harmful Algal Bloom and Hypoxia Research and Control Act (HABHRCA).

We study and fund research on causes and impacts of hypoxia and harmful algal blooms, implementing HABHRCA on behalf of NOAA. We develop management strategies to reduce nutrient inputs into coastal waters, mitigate hypoxia and protect coastal ecosystems.

For example, in the Gulf of Mexico, NCCOS-sponsored research has been used to set goals and prioritize actions for reducing the size of the hypoxic zone by the Gulf of Mexico/Mississippi River Watershed Nutrient Task Force. Our work is done in collaboration with state and federal government, academia and industry partners.