| There is still much that is not known about the dead zone, including all of its possible economic and ecological implications. |
Every spring and summer, creatures that cannot swim away are smothered in oxygen-depleted water at the bottom of the northern Gulf of Mexico. Some years, this hypoxic or "dead zone" off the Louisiana-Texas coast has grown as large as the state of Massachusetts.
This hypoxic zone potentially puts at risk gulf fisheries—a $26 billion-a-year industry that provides the nation with more shrimp, oysters, and fish than anywhere outside Alaska.
In the late 90s, six teams of scientists, working together with the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, were asked to determine what causes the dead zone and what could be done about it.
The task force determined that the main cause is excess nutrients, especially nitrogen, washed into the gulf from the Mississippi River, which drains 40 percent of the lower 48 states. On October 11, 2001, federal and state officials announced an ambitious $1-billion-per-year plan to reduce the gulf hypoxic area to one-fourth its largest size by 2015.
Scientists now complain that due to lack of money and political will little of the mostly voluntary plan has been implemented.
"The task force still meets, but there is no new money to support the various activities, especially management," says Nancy Rabalais, professor at the Louisiana Universities Marine Consortium and one of the lead researchers of the gulf hypoxic zone.
To significantly reduce the size and impact of the gulf's dead zone, researchers believe that a nationally coordinated and wholly funded initiative is necessary. While the nation's priorities are elsewhere, however, the land-use planning, pollution prevention, coordination, and educational efforts of state and local coastal and inland resource managers have the potential to become even more important.
With "hypoxic areas developing in estuaries and coastal areas throughout the U.S.," Rabalais warns, addressing or preventing the development of similarly oxygen-deprived areas should be a concern for all coastal managers.
Sizing Up the Source
One of the largest rivers in the country, the Mississippi drains 31 states from Montana to New Mexico to New York, including nearly every state between the Rockies and the Appalachians. Fertilizers, sewage treatment waste water, animal waste, industrial wastes, and atmospheric pollutants all contribute nitrogen and phosphorus to the Mississippi.
Over the years, the Mississippi watershed has had millions of acres of wetlands and bottomland forests—the natural filters of nutrient-rich runoff—drained for farmland and development, or separated from the river by a huge system of levees built to contain floodwaters.
Every summer, the excess nutrients from the runoff feed an explosion of algae growth, which eventually dies and sinks. As the dead material decomposes, oxygen is depleted from bottom waters, which remain relatively undisturbed by the gulf's summertime low winds and calm seas. When hypoxia sets in, sea life can no longer survive.
While it is unknown how long hypoxia has been occurring in the gulf, studies show that the level of oxygen depletion has steadily worsened over the past two centuries, rapidly accelerating since the 1950s. The Gulf of Mexico's dead zone is now one of the largest areas of anthropogenic coastal hypoxic water in the world, says Rabalais.
"I think it's a mistake to try to separate the gulf's hypoxia from the problems of wetlands losses in the Mississippi delta and throughout the Mississippi basin," says John W. Day, distinguished professor in the Department of Oceanography and Coastal Sciences at Louisiana State University. "This needs to be looked at as a basin-wide problem with the solutions distributed throughout the Mississippi basin."
How Serious Is Serious?
What researchers know is that unless the nutrient load entering the northern gulf is reduced, hypoxia will appear each summer over large areas. There is still much that is not known about the dead zone, including all of its possible economic and ecological implications.
Rabalais notes that the limited number of economic studies done show the hypoxic zone causes "no documentable economic impacts," but "that doesn't mean there are no impacts. The data needed to determine the actual impacts doesn't exist. . . What we don't know is how the overall productivity of the system has changed."
Not only do the impacts on the gulf need more study, asserts Day, but also the impacts on the entire Mississippi watershed need to be taken into account.
"The value of the Mississippi basin is hundreds of billions of dollars," Day explains. "This is the agricultural base of the U.S. The Mississippi River provides transport for more than 472 million tons of cargo each year. It's enormously important that we begin to see the relationship between good economic value and good environmental quality."
Day adds, "If we are not paying attention, in a sense, we're being a little bit foolish."
What's the Plan?
Among the actions in the plan set out by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force were restoring wetlands and forest buffers along waterways, establishing a nitrogen-credit system with incentives for the agricultural industry to reduce its application of nitrogen-based fertilizers, controlling urban and suburban nonpoint sources of pollution, and upgrading sewage treatment plants.
While a number of the initiatives in the plan are under way, Day says, national coordination, prioritization, and collaboration are missing.
Day and a partnering scientist in Ohio estimate that "if just two percent of agricultural land in the Mississippi basin was strategically selected and made into wetlands areas, we could probably reduce 50 percent of the nitrogen getting into the Mississippi River." Other benefits might result, as well, such as reduced flooding.
Chris Piehler, senior environmental scientist for the Louisiana Department of Environmental Quality, suggests that state and local efforts to address water quality problems and control pollution could play an increasingly important role in reducing runoff that results in hypoxic areas.
"If we can get everyone to take care of their own water quality problems, the Gulf of Mexico will benefit," Piehler says.
"In whatever regulatory capacity coastal resource managers make decisions, they should take into account the whole watershed and what is happening to it," Rabalais says. "They need to be cognizant and supportive of anything that is shown to be a good concept for the management of nutrients."
She adds, "It's going to take everybody working together" to reduce the gulf's hypoxic zone. "We're going to have to work beyond traditional boundaries."
For more information on the hypoxic area in the Gulf of Mexico , contact Nancy Rabalais at (985) 851-2836, or nrabalais@lumcon.edu; John W. Day at (225) 578-6508, or johnday@lsu.edu; or Chris Piehler at (225) 219-3609, or chris.piehler@la.gov.
