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Coastal Desk

Gulf Dead Zone Largest Ever This Year

The "dead zone" refers to areas of the Gulf that are low in oxygen. It's fueled largely by agricultural runoff carried by the Mississippi River from the Midwest.

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.


“And that leaves an incredibly large area where a shrimper could not catch anything,” says Nancy Rabalais, a Louisiana State University ecologist and study author.


Rabalais says size of the dead zone has to do with two factors: the amount of nitrates in the river, and the amount of water in the river.


She says the dead zone might actually be even bigger, but they ran out of time to study it.


“I only had eight days,” she says, “and at some point I had to turn the ship around and get it back to port.”


Rabalais says nitrates have been steadily increasing since the 50’s as farmers use more fertilizer -- and this year the Mississippi spat an above-average amount of water into the gulf.


Support for the Coastal Desk comes from the Walton Family Foundation, the Coypu Foundation, the Greater New Orleans Foundation, and local listeners.

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