Spring floods increase chance of large Gulf of Mexico 'dead zone' ANN ARBOR, Mich., June 19 (UPI) -- Spring floods across the Midwest are expected to result in a very large and potentially record-setting 2013 Gulf of Mexico "dead zone," researchers say. Farmland runoff containing fertilizers and livestock waste, some of it from as far away as the Corn Belt, is the main source of the nitrogen and phosphorus that cause the annual Gulf of Mexico hypoxic zone, an oxygen-depleted area researchers said could reach 8,500 square miles this year. Such an extent would place it among the 10 largest on record, a release from the University of Michigan said Wednesday. In 2008, the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, a coalition of federal, state and tribal agencies, set the goal of reducing average extent of the gulf hypoxic zone to 1,950 square miles by 2015. Since 1995 the gulf dead zone has averaged 5,960 square miles, an area roughly the size of Connecticut, researchers said. "The size of the gulf dead zone goes up and down depending on that particular year's weather patterns," U-M aquatic ecologist Donald Scavia said. But the bottom line is that we will never reach the action plan's goal of 1,950 square miles until more serious actions are taken to reduce the loss of Midwest fertilizers to the Mississippi River system, regardless of the weather.