The dead zone is an area in the Gulf of Mexico where the oxygen is so low that fish and shrimp can’t live.
Scientists say this year’s dead zone is 8,776 square miles now -- about the size of New Jersey. Over the last five years it’s averaged 5,543 square miles.
It’s caused largely by agricultural runoff from the Midwest, and brought downstream by the Mississippi River. That runoff is high in nitrates, from fertilizer, which causes algae to bloom. When the algae dies, it sucks oxygen out of the water.