Jul 28, 2012 2:36 PM by AP
NEW ORLEANS (AP) - This year's Gulf of Mexico "dead zone," an area of low oxygen that develops every spring and summer, is the fourth-smallest since measurements of the zones began in 1985, a new report says.
The zone measured 2,889 square miles, said the report released Friday by the Louisiana Universities Marine Consortium.
The dead zone forms because fertilizer and other nutrients run into the Mississippi River, which empties into the Gulf. The nutrients feed huge numbers of microscopic organisms. When they die, their decomposition uses up oxygen. It is a recurring problem affecting sea life off the Louisiana coast, and sometimes the coasts of Mississippi and Texas.
Last year's hypoxic zone was about 6,765 square miles. The record is 8,400.
The consortium said the dead zone is relatively small this year because record drought across the country meant fewer nutrients were washed into the river - not because needed steps have been taken to prevent the runoff.
"The issue of nutrient overload, of both nitrogen and phosphorus, remains a critical issue for the health of water bodies within the Mississippi River Basin and in the northern Gulf of Mexico. Efforts should continue in full force to reduce nutrient loads," the LUMCON report said.
LUMCON Chief Scientist Nancy Rabalais noted that the distribution of low-oxygen waters along Louisiana's continental shelf differed from years past.
"There was a narrow band close to the Mississippi River and large, non-hypoxic area between there and the Atchafalaya River," the report said.