Researchers say this year’s "dead zone" in the Gulf of Mexico is the largest on record.
This week, NOAA announced that this year's dead zone is the biggest one ever measured.
It covers 8,776 square miles — an area the size of New Jersey.
Previous estimates were that the dead zone would be about 6700 square miles – federal researchers said the larger than expected zone was caused by unusually heavy rains in the Midwest, which flushed a lot of nutrients into the Gulf.
The Gulf dead zone forms each spring and summer off the Louisiana and Texas coast when oxygen levels drop too low to support most life in bottom and near-bottom waters.
The zone is caused by nitrates and nitrogen from fertilizer and urban runoff flowing down the Mississippi River.
The amount of nitrogen entering the Gulf of Mexico each spring has increased by about 300 percent since the 1960s, mainly due to increased agricultural runoff.
The largest hypoxic zone measured before this year occurred in 2002 and encompassed more than 8,400 square miles.