The fish-killing “dead zone” in the Gulf of Mexico this summer covers 6,952 square miles, midway in size between Connecticut and New Jersey, said researchers on Thursday. It is the eighth-largest dead zone in 33 years of keeping records, despite the diluting effects of Hurricane Barry, which stirred the gulf a few days before the start of the annual survey that measures the extent of the hypoxic waters.
Nutrient runoff from cities and farms — fertilizer, manure, and sewage are examples — in the Mississippi River basin stimulates algal growth during the spring and summer. Oxygen-consuming bacteria eat the algae when they die. The oxygen content of water near the bottom is too low to support most marine life, a condition called hypoxia.
“Past research indicates that hypoxia can take a week to reform in the summer after major wind events such as the recent passage of Hurricane Barry,” said professor Nancy Rabalais of Louisiana State University, the survey leader. “We found that, despite the storm, the zone reformed and was in the process of rapidly expanding.” This year’s survey began four days after Barry passed through the region.
This year’s dead zone was more than three times larger than the goal of 1,900 square miles set by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force. Created in 1997, the task force of federal and state officials aims to coordinate activities intended to reduce the size, severity, and duration of the dead zone.
“We know which projects, practices, and policies would reduce nutrient pollution, but not enough has been done to implement these commonsense measures in communities and on farms,” said the National Wildlife Federation, which criticized the Trump administration as a poor steward. The environmental group Mighty Earth said that “uncontrolled runoff from industrial meat production” — feedlots and grain farms — “is known to be the main source of pollution causing the dead zone.”