NEW ORLEANS - High rivers and high levels of nitrogen and phosphorus from farm and urban runoff mean a larger than average oxygen-starved “dead zone” is likely this year in the Gulf of Mexico, researchers said Wednesday.

But the predicted area for an area with too little oxygen for marine life is nowhere near a record, the National Oceanic and Atmospheric Administration said in a news release.

“Each year, the forecasts are reported to be bigger or smaller than some long-term average, when in fact the long-term average is not acceptable,” Don Scavia, professor emeritus at the University of Michigan School for Environment and Sustainability and one of the scientists who works on the forecast, said in a news release.

“We can’t control the weather; keeping nutrients out of streams and rivers should be our focus,” Nancy Rabalais of the Louisiana Universities Marine Consortium, who has been mapping the dead zone since 1985, said in an email.

The area forms every summer off Louisiana and stretches into Texas waters, starting at the sea floor and extending upward. It’s created as calm weather lets fresh river water form a layer above the denser salt water in the Gulf of Mexico. Fertilizer and other nutrients in the fresh water feed algae, which die and then decompose on the sea floor, using up oxygen.

This year’s low-oxygen area is expected to cover about 6,700 square miles (17,350 square kilometres), NOAA said in a news release. That's about the size of the southern African nation of Eswatini.

The average is nearly 5,400 square miles (14,000 square kilometres). The record from 2017 is nearly 8,800 square miles (22,800 square kilometres).

If there's a tropical storm during the two weeks before the summer measurement cruise, it would stir up the water and reduce the area covered by about 30%, the forecast noted.

Hurricane Barry reduced last year's hypoxic zone, but it was still the eighth-largest on record.

Scavia noted that federal-state plans to reduce the size of the dead zone by reducing runoff pollution have been in place for nearly two decades. "Clearly, something different needs to be done in the watershed to actually reduce the nutrient loads and reduce the size of the dead zone,” he said.

News from © The Associated Press, 2020