Every spring for many years now, a dead zone has formed in the Gulf of Mexico just south of the Mississippi River Delta. This patch of water contains less than 2 milligrams of oxygen per liter, which is too little to sustain most aquatic life. For the past 5 years, this dead zone reached its maximum size—on average, 5,500 square miles, or roughly the size of Connecticut—around midsummer and disappeared in the fall.
Last month, 10 federal agencies entered an agreement with nine states and two Indian tribes to work together to stem the pollution that creates this parcel of oxygen-starved water. Their goal is to halve the Gulf's dead zone by 2015.
Throughout the Midwest, nutrients—principally nitrogen and phosphorus—rain out of the air or run off farms and other lands and end up in streams. Eventually, these remnants of fertilizers and other sources of pollution flow down the Mississippi and spew into the Gulf. There, the nutrients spur algae blooms