Gulf of Mexico’s ‘Dead Zone’ Grows as Spill Impact Is Studied

The Gulf of Mexico faces a renewed and enlarged threat to marine life: a low-oxygen “dead zone” about the size of Massachusetts, caused by chemical runoff into the Mississippi River that flows into the sea.

The dead zone, which occurs in Gulf waters in summer and is unrelated to BP Plc’s oil spill, covers an area twice as large as last year, according to a National Oceanic and Atmospheric Administration study released this week. The low-oxygen area this year is the fifth-largest since measurements began in 1985.