Scientists forecast an "average size" dead zone in the Gulf of Mexico in 2018

Scientists forecast an "average size" dead zone in the Gulf of Mexico in 2018
Scientists deploy a water sensor to test oxygen levels in the Gulf of Mexico (LUMCON)

(WVUE) - Government scientists forecast a dead zone of approximately 5,780 square miles this summer in the Gulf of Mexico, a size similar to the 33-year average.

A report from the National Oceanic and Atmospheric Administration predicts the area of low oxygen will be considerably smaller than last year's record 8,776 square miles.

The Gulf's annual low oxygen, or hypoxic zone, is caused by excess nutrients flowing primarily from the Mississippi River into the Gulf from urban runoff and agricultural sources.

Scientists say the excess nutrients stimulate an overgrowth of algae, which then sinks and decomposes in the water. The resulting low oxygen levels near the bottom are insufficient to support most marine life in the area, which scientists have dubbed a "dead zone."

"The Gulf's recurring summer hypoxic zone continues to put important habitats and valuable fisheries at risk," said Steve Thur, Ph.D., director of NOAA's National Centers for Coastal Ocean Science in a statement.

"Although there has been some progress in reducing nutrients, the overall levels remain high and continue to strain the region's coastal economies."

Even though NOAA is predicting an average dead zone this summer, the dead zone remains three times larger than the long-term target set by the Interagency Mississippi River and Gulf of Mexico Hypoxia Task Force, a group charged with reducing the Gulf dead zone.

Higher river discharges in late spring carry a larger nutrient load into the Gulf.

While the Mississippi River was unusually high over the winter and early spring months, NOAA points out the discharge from the Mississippi and Atchafalaya rivers was only about four percent above the long term average during the month of May.

Nitrate loads were about 13 percent below the long-term average, and the phosphorus loads were about 10 percent above the long-term average, according to this year's study.

"While recent trend results show nutrient loads decreasing in some areas of the Mississippi-Atchafalaya watershed, on balance there has been little change in loading to the Gulf in recent decades," said Don Cline, associate director for the USGS Water Mission Area.

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