Dead zone is not a record setter thanks to hurricane

Tuesday, July 29, 2008 at 3:00 p.m.

HOUMA — This year’s dead zone — the area of low-to-no oxygen that settles off Louisiana’s coast every summer — was smaller than expected because Hurricane Dolly churned the Gulf’s waters and curbed the phenomenon, according to Louisiana scientists.
But that doesn’t mean this year’s dead zone is small. The size is close to the one in 2001, which was the largest ever recorded, said LUMCON Director Nancy Rabalais.
This year’s dead zone covers about 8,000 square miles, similar to last year’s size and slightly less than the 8,006-square miles recorded in 2001.
It is the second largest measured since mapping began in 1985. Scientists had previously predicted this year’s dead zone could be a record-breaking 8,800 square miles.
The 12-member research team — scientists and graduate students from the Louisiana Universities Marine Consortium, or LUMCON, Louisiana State University and the University of Iowa — finished the annual mapping survey Monday.
"If it were not for Hurricane Dolly, the size of the dead zone would have been substantially larger," Rabalais said.
But "an amazingly large area" of low oxygen persists despite the hurricane’s churning action, she added, which returned oxygen to the dead zone’s edges, Rabalais said.
The dead zone emerges each summer and lasts through early fall.
It is caused when nutrients from fertilizer and other human activities are washed down the Mississippi River and into the Gulf. The nutrients fertilize algae, which suck up oxygen as it decomposes, leaving fish and other marine life without the oxygen they need to survive. The organisms that can flee survive, and the ones that can’t suffocate.
Increased farming of corn and other crops for alternative fuels, such as ethanol, have worsened the dead zone, scientists say.
This year’s dead zone got a boost from spring flooding in the Mississippi River. In addition, June floods in the Midwest aggravated an already worsening situation offshore, Rabalais said.
"Low-oxygen conditions were present off Terrebonne and Barataria bays since March and continued to increase through the spring and summer," Rabalais said.
But tropical storms and hurricanes have the potential to mix waters, bringing oxygen back to dead-zone bottoms and curbing the phenomenon — which is exactly what Hurricane Dolly did as it crossed the Gulf of Mexico last week en route to Brownsville, Texas, Rabalais said.