A massive area of water off the Louisiana coast that is almost devoid of oxygen and unable to sustain marine life is set to get even bigger.

Louisiana Universities Marine Consortium released a forecast Monday predicting that the world's second-biggest "dead zone," located in the northern Gulf of Mexico at the end of the Mississippi River, is set to reach 22,015 square kilometres this summer.

That would be its largest size since mapping began in 1985. The biggest previous measurement of the zone was 21,999 square kilometres five years ago.

The scientific word for "dead zone" is hypoxia or low oxygen, caused by pollution from many sources such as fertilizer, soil erosion and discharge from sewage treatment plants.

Nutrients flowing down a river into a larger body of water can spur the growth and death of algae, which absorbs available oxygen faster than it is created. In turn, that can cause sea life such as fish, shrimp and crabs to move elsewhere or die, according to the consortium website.

Over the past 50 years, the volume of nutrients flowing down rivers such as the Mississippi into the Gulf has tripled, according to BBC News, and has consequently caused a rise in attacks by sharks, which flee oxygen-deprived waters.

For the prediction, researchers took into account the amount of nitrogen found in the Mississippi in May and the amount of water flowing down the river to the gulf. Actual results will follow a week-long survey of the waters set to begin later this summer.