Q&A: Hurricanes affect dead zone in Gulf of Mexico

By Times staff
December 30, 2008; St. Petersburg Times


Hurricanes affect dead zone
Did this year’s hurricane season affect the oxygen-depleted "dead zone" in the Gulf of Mexico?
"Most certainly," says Steve DiMarco, a Texas A&M University oceanography professor who for 16 years has studied the Gulf of Mexico, which has a "dead zone" where oxygen-depleted water can kill marine life.
In early July, most of the Texas-Louisiana shelf from Freeport, Texas, to the Mississippi River Delta was hypoxic — meaning the saltwater has lost large amounts of oxygen. Later in July, Hurricane Dolly disrupted the dead zone and re-oxygenated the shallow waters south of Louisiana and the entire shelf off Texas. Oxygen levels started to drop again within days after the storm.
In early August, Hurricane Eduard re-oxygenated the entire Louisiana shelf, but by mid-August the oxygen concentrations dropped to hypoxic levels.
Again, winds from Hurricane Gustav re-oxygenated the dead zone Sept. 1, and oxygen levels began receding after that storm.
And guess what? Hurricane Ike re-oxygenated the shelf when it made landfall Sept. 12 in Texas.
The latest data showed oxygen concentrations nearly all at normal levels, DiMarco said.
"The system should stay oxygenated until next spring, when winter runoff increases, and summer heating makes conditions more favorable for hypoxia (and dead zone formation) to exist," he said.