ANN ARBOR, Mich.---Extreme flooding of the Mississippi River this spring is expected to result in the largest Gulf of Mexico "dead zone" on record, according to a University of Michigan aquatic ecologist and his colleagues.
The 2011 forecast, released today by the U.S. National Oceanic and Atmospheric Administration (NOAA), calls for a Gulf dead zone of between 8,500 and 9,421 square miles, an area roughly the size of New Hampshire.
The most likely 2011 scenario, according to U-M's Donald Scavia, is a Gulf dead zone of at least 8,500 square miles, surpassing the current record of 8,400 square miles, set in 2002. The average over the past five years is about 6,000 square miles.
"Stream flows were nearly double normal during May, delivering massive amounts of nutrients to the Gulf, and that's what drives the dead zone," said Scavia, Special Counsel to the U-M President for Sustainability, director of the Graham Sustainability Institute, and a professor at the School of Natural Resources and Environment.
Farmland runoff containing fertilizers and livestock waste---some of it from as far away as the Corn Belt---is the main source of the nitrogen and phosphorus that cause the annual Gulf of Mexico oxygen-starved, or hypoxic, zone. Each year in late spring and summer, these nutrients flow down the Mississippi River and into the Gulf, fueling explosive algae blooms there.
When the algae die and sink, bottom-dwelling bacteria decompose the organic matter, consuming oxygen in the process. The result is an oxygen-starved region in bottom and near-bottom waters: the dead zone.
This year, stream-flow rates in the Mississippi and Atchafalaya Rivers were nearly double normal during May 2011, significantly increasing the amount of nitrogen and phosphorus transported by the rivers into the Gulf.
According to U.S. Geological Survey estimates, 164,000 metric tons of nitrogen were transported in May 2011 to the nort
|Contact: Jim Erickson|
University of Michigan