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Overview of Hypoxia and Nutrient Pollution

Why is this issue important?

Hypoxia is a major concern for many of our nation's waterways. Hypoxia occurs when the amount of dissolved oxygen in water becomes too low to support most aquatic life (typically below 2 mg/l).  Most organisms avoid waters that are hypoxic because it can cause physiological stress and impact their growth, reproduction, and survival. If organisms cannot escape, hypoxia can be fatal, reducing overall populations and, in some cases, negatively affecting commercial and recreational harvests of fish and shellfish. While hypoxia can occur naturally, the frequency and intensity of occurrence in coastal areas is increasing, largely due nutrient pollution (such as nitrogen and phosphorus) from human activities. Over half of the U.S. estuaries now experience natural or human-induced hypoxic conditions at some time each year and evidence suggests that the frequency and duration of hypoxic events have increased over the last few decades.

The importance and national scale of hypoxia in U.S. waters is evidenced by the recently documented exponential increase in number of coastal systems experiencing hypoxia worldwide and in the US (Diaz & Rosenberg 2008, Science).  Congress has responded with the reauthorization in 2004 of the Harmful Algal Bloom and Hypoxia Research and Control Act (HABHRCA). A series of national reports describe the need and identify priorities for research and management related to nutrient inputs and hypoxia in U.S. coastal waters (e.g. Reports by the Committee on the Environment and Natural Resources and the National Academy of Science)

How are we addressing this issue?

The goal of CSCOR hypoxia programs is to provide timely and high-quality scientific results that can be used by natural resource managers in an effort to restore and protect coastal ecosystems. CSCOR-sponsored scientists and their partners in government, academia and industry are seeking ways to better understand the causes of hypoxia, especially nutrient over-enrichment, and its impacts on living resources.

In addition to improving the scientific understanding of hypoxia, CSCOR is also actively engaged with partners in state and federal government, academia and industry to apply this understanding towards the development of management strategies that will reduce nutrient inputs into coastal waters, mitigating hypoxia and protecting coastal ecosystems. This is best exemplified in the Gulf of Mexico, where CSCOR-sponsored research has been directly applied to the setting of goals and actions for reducing size of the hypoxic zone by the Gulf of Mexico/Mississippi River Watershed Nutrient Task Force.