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Scientists Work for a Better Understanding of the Causes and Cures of Hypoxia in the Gulf of Mexico


NOAA’s National Centers for Coastal Ocean Science  is sponsoring the multi-year, interdisciplinary Northern Gulf of Mexico Coastal Ecosystem Research Project, with the ultimate goal of enabling improved predictions of future effects of nutrient loading, eutrophication, hypoxia, and climate change on the Gulf of Mexico ecosystem.


The incidence of severe oxygen depletion, either hypoxia (<2 mg of oxygen per liter), or anoxia (0 mg/l), is a growing concern for U.S. estuarine and coastal waters. Increased primary production in the offshore Mississippi River plume and strong water column stratification lead to hypoxia. Prolonged oxygen depletion can cause mass mortalities of aquatic life, with disastrous consequences to coastal commercial fisheries.

Since NCCOS’s inception, its sponsored investigators have documented a hypoxic zone (the dead zone) on the Louisiana continental shelf with seasonally depleted oxygen levels. Computer models and scientific research have established a strong link between nutrient loading from the Mississippi and Atchafalaya River system and this hypoxia.

Graph of Comparive Size of Hypoxia Area:1995-2001From 1990 – 1996, NOAA sponsored the Nutrient Enhanced Coastal Ocean Productivity (NECOP) study, with the goal of understanding the effect of anthropogenic nutrient loading on the shelf waters of Louisiana and Texas.

Forty academic and federal scientists from fourteen institutes joined in the interdisciplinary NECOP investigation, which helped document the extent of nutrient input and hypoxia in the northern Gulf of Mexico and establish a direct link between increasing river-borne dissolved nutrients, hypoxia in the bottom waters and the associated ecological changes.

Despite increased awareness of the causes of hypoxia, the largest hypoxic zone ever – approximately the size of the State of Massachusetts – was recorded in July of 2001.

Recent Direction

In 2000, an integrated assessment of hypoxia in the Northern Gulf of Mexico concluded that the complex nature of nutrient cycling and transport within the system requires an adaptive management scheme.Long-term monitoring, research, and assessment will provide managers with continual feedback, allowing management actions to adjust to interpretations of new scientific information.

Mississippi River Basin with Gulf of Mexico HypoxiaTo address these recommendations, NCCOS initiated the Northern Gulf of Mexico Coastal Ecosystem Research Project in 2000. They published the first Announcement of Opportunity to submit research proposals in March 2000 from which three projects were initiated.

The primary focus of this first year of funding was monitoring the spatial and temporal changes in the distribution of the hypoxic zone. Studies were also initiated to extend modeling efforts to predict changes in oxygen budgets and severity of hypoxia under altered hydrologic scenarios and to better define the relationships among nutrient fluxes, nutrient ratios, phytoplankton species composition, and carbon production and flux. Carbon (i.e. organic material) flux fuels the growth of the hypoxic zone.

In January 2001, a second Announcement of Opportunity to submit research proposals was published, resulting in the initiation of three projects investigating the effects of the hypoxic zone on fisheries.

The next An Announcement of Opportunity was to solicit proposals for research projects to initiate modeling studies for the region, and support for observational studies necessary to support the modeling studies.

The overall goal of the project is to obtain the ability to input different possible physical forcing and nutrient loading scenarios into a predictive model for the region in order to predict the effects on the oxygen concentrations and the biological system, including the effects on economically and ecologically important species.

NCCOS’s intent is to provide timely and high-quality scientific results that can be used in an adaptive management program to restore and protect the Louisiana continental shelf ecosystem.

For more information on current NCCOS funded research in Northern Gulf of Mexico, visit our website at

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