A season of heavy flooding in the Mississippi River valley has poured fertilizer into the Gulf, sending nitrogen levels 35 percent higher than the 32-year average. The runoff water is perfect for algae blooms, which consume oxygen and cause marine life to abandon the northern Gulf or die. The dead zone is now on track to cover between 8,500 and 9,400 square miles, more than the 8,400 square miles recorded in 2002. The extra runoff is also slowing recovery from last summer's Deepwater Horizon disaster, which released upwards of 200 million gallons of oil into the ocean.
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