Hurricane Dolly caused plenty of misfortune, as downpours and flooding forced hundreds of people from their homes in Texas and New Mexico. But if there's any kind of positive side to a natural disaster, it could be that Dolly might have decreased the size of the Gulf of Mexico's dead zone. The dead zone starts near the Mississippi River delta and extends toward the Texas coast. Nutrients like nitrogen and phosphorus wash into the river via runoff and are carried to the gulf, where their decomposition uses up oxygen. Also, the river's freshwater and the gulf's saltwater don't mix well and tend to form layers, which can keep oxygen from getting to the bottom of the gulf. That creates the dead zone—an area of low-oxygen water where most marine creatures can't live. Because the Mississippi River's nitrogen content was especially high this year—37 percent higher than last year—some experts predicted that we'd see an enormous dead zone in 2008, perhaps as big as 8,800 square miles. But along came Dolly, churning up the sea in its path. Because the hurricane mixed up the waters,
Nancy Rabalais of the
Louisiana Universities Marine Consortium says that the dead zone will be a little bit smaller than those predictions, only about 8,000 square miles. Don't uncork the champagne—that size is still close to the record set in 2001. And runoff from the massive Iowa floods in June could send more nutrients toward the gulf, canceling out any benefits from Dolly. Image: NASA/Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center
