Action plan to halve Gulf of Mexico ‘dead zone’

The US Environmental Protection Agency, together with federal and regional bodies has developed an action plan to reduce the size of the ‘dead zone’, a large, oxygen-starved area of the Gulf of Mexico which threatens the nation's most productive and valuable fishing grounds.

The ‘dead zone’, so-called because some organisms die while others flee the area, is affected by hypoxia (lack of oxygen), and affects an area that over the last five years has averaged almost 5,500 square miles (14,000 sq km), off Louisiana’s coast, home to approximately 40% of US fisheries and is the largest such area in the western Atlantic Ocean. Scientific evidence indicates that excess nitrogen from the Mississippi and Atchafalaya River drainage basins drives the onset and duration of hypoxia in the Gulf of Mexico during the summer months.

On 18 January, the EPA, nine other federal agencies, nine states along the Mississippi River, and two tribes announced a plan to work together to cut the ‘dead zone’ by about half its average size over the next 15 years. An action plan to combat the problem, which has increased significantly in the last 50 years, and has lead to the loss of shrimp, crabs, zooplankton, and other important fish, was made obligatory by Congress in 1998.

Sources of the excess nitrogen include discharges from sewage treatment and industrial wastewater treatment plants and stormwater runoff from city streets and farms. Nutrients from automobile exhaust and fossil fuelled power plants also enter Gulf through air deposition to the land area drained by the Mississippi River and its tributaries. Much of the nitrogen entering the Gulf comes from drainage from agricultural and urban lands far removed from the Gulf, including Iowa, Illinois, Indiana, southern Minnesota, and Ohio. About 90% of the nitrates entering the Gulf come from runoff and 56% enter the Mississippi River above the Ohio River.

It is estimated that a reduction of at least 20% in the amount of nutrients entering the Gulf is necessary to have a significant positive effect on marine life, but a 40% reduction in total nitrogen entering the Gulf is believed essential to return nitrogen levels to 1955-70 levels when hypoxia was less of a problem.

The agreed Hypoxia Action Plan includes setting reduction targets for nitrogen discharges to surface waters, establishing a baseline of existing efforts for nutrient management, identifying opportunities to restore flood plain wetlands (including restoration of river inflows) along and adjacent to the Mississippi River, and detailing needs for additional assistance to meet their goals. Under the Action Plan, states, tribes and relevant federal agencies, working as river-basin committees, would have flexibility to develop the most effective and practical strategies to reduce discharges of excess nutrients to their waters. The strategies are expected to rely heavily on voluntary and incentive-based approaches for dealing with agricultural and urban runoff, restoring wetlands, and creating vegetative or forested buffers along rivers and streams within priority watersheds. The plan also calls for new resources to fund these activities.

“This landmark agreement will help protect the Gulf of Mexico,” said EPA Assistant Administrator for Water J. Charles Fox. “We are especially pleased that all nine states along the Mississippi River have committed to work with the federal government to resolve a national water quality problem.”

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