Environment

The Gulf of Mexico’s ‘Dead Zone’

The oxygen-poor “dead zone” in the Gulf of Mexico may be the biggest on record this year, nearly doubling in size to cover an area of ocean as large as Vermont, scientists at Louisiana State University estimate.

The dead zone develops when nitrogen-rich runoff from the Midwestern farm belt pours into rivers and out into the Gulf. That runoff is loaded with fertilizer, as well as nutrients from animal and human waste, and it fuels the growth of algae that die, sink, and decompose, depleting oxygen levels offshore. That drives away marine life in the zone — or kills species that can’t escape.