According to U.S. Geological Survey estimates, the Mississippi and Atchafalaya rivers transported 58,100 metric tons of nitrogen (in the form of nitrite plus nitrate) to the northern Gulf in May 2012, an amount that is 56 percent lower than average May nitrogen loads estimated in the last 33 years.
"These forecasts are the product of decades of research, monitoring and modeling on how decisions we make in the vast drainage basin of the Mississippi and its tributaries translates into the health of the coastal zone of the Gulf of Mexico," said U.S. Geological Survey Director Marcia McNutt. "Comparing the actual hypoxic zone against the predictions will help scientists better understand the multiyear memory of this complex land-sea system, and ultimately better inform options for improving ecosystem productivity."
About a thousand miles northeast of the Gulf of Mexico in Chesapeake Bay, this year's hypoxic zone is expected to measure about 1.5 cubic miles, Scavia said. That's about average compared to measured volumes since 2000 but much smaller than last year's record-setter of 2.75 cubic miles, which was due to spring storms that washed large amounts of nutrients into rivers that feed the Bay.
So far in 2012, rainfall in the Chesapeake Bay watershed has been 50-to-75 percent of normal, Scavia said.
The actual size of the 2012 Gulf hypoxic zone will be announced following a NOAA-supported monitoring survey led by the Louisiana Universities Marine Consortium between July 27 and Aug. 3.
The amount of nitrogen entering the Gulf of Mexico each spring has increased about 300 percent since the 1960s, mainly due to increased agricultural runoff. The Gulf of Mexico/Mississippi River Watershed Nutrient Task Force has targeted 1,
|Contact: Jim Erickson|
University of Michigan