Yale Environment 360, August 24, 2012
U.S. scientists say the nation’s worst drought in five decades has had at least one positive effect: the smallest so-called “dead zone” seen in the Gulf of Mexico in years. In a 1,200-mile research cruise conducted in the waters of the gulf this month, scientists from Texas A&M University found only 1,580 square miles of oxygen-depleted, or hypoxic, water in the gulf, compared with 3,400 square miles last August. The hypoxic zone is created when algal blooms, caused by large amounts of fertilizer and nutrients washing into the gulf, remove oxygen from the water and suffocate marine life. According to the researchers, hypoxia was found only in the waters near the Mississippi River delta — which accounts for nearly 90 percent of all freshwater runoff in the gulf — and no hypoxia was observed off the Texas coast. “What has happened is that the drought has caused very little fresh-water runoff and nutrient load into the gulf, and that means a smaller region for marine life to be impacted,” said Steve DiMarco, an oceanography professor at Texas A&M.