Scientists are predicting that the "dead zone" at the mouth of the Mississippi River in the Gulf of Mexico could be the largest ever this year, due in part to severe flooding and record-level plantings of corn and soy bean crops.
The dead zone is an area in the Gulf of Mexico where seasonal oxygen
levels drop too low to support most life in bottom and near-bottom
waters. This low oxygen, or hypoxic, area is primarily caused by high
nutrient levels, which stimulates an overgrowth of algae that sinks and
decomposes. The decomposition process in turn depletes dissolved oxygen
in the water. The dead zone is of particular concern because it
threatens valuable commercial and recreational Gulf fisheries.
National Oceanic and Atmospheric Administration-supported scientists from the Louisiana Universities Marine Consortium and Louisiana State University are predicting the area could measure a record 8,800 square miles, or roughly the size of New Jersey.
In 2007, the dead zone was 7,903 square miles. The largest dead zone on record was in 2002, when it measured 8,481 square miles. The official measurement of this year’s dead zone is slated to be released in late July. Researchers began taking regular measurements of the dead zone in 1985.
"The prediction of a large dead zone this summer is due to a combination of large influx of nitrogen and exceptionally high flows from the Mississippi and Atchafalaya rivers," said LSU scientist R. Eugene Turner.
Research indicates that the nearly tripling of nitrogen levels into the Gulf over the past 50 years from human activities has led to a dramatic increase in the size of the dead zone.
"The strong link between nutrients and the dead zone indicates that excess nutrients from the Mississippi River watershed during the spring are the primary human-influenced factor behind the expansion of the dead zone," said Rob Magnien, director of NOAA’s Center for Sponsored Coastal Ocean Research. "This analysis will greatly inform the development of federal, state and local efforts to reduce the dead zone’s size."
Record corn harvests throughout the Midwest are clearly adding to the problem, according to Eugene Turner, a scientist with LSU, and leader of the research team.
U.S. farmers are planting "an awful lot of corn and soybeans," he told reporters, adding that both crops leach nitrogen easily into soil and groundwater.
An estimated 87 million acres of corn were planted this year. Demand for the crop has been driven up by increased ethanol production for use as a transportation fuel.
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