Floodwaters causing new Gulf of Mexico dead zone off Texas

FILE - A bird stands on an oyster shell strip atop an existing reef in the Gulf of Mexico off the Texas coast. (AP Photo/Pat Sullivan)
FILE - A bird stands on an oyster shell strip atop an existing reef in the Gulf of Mexico off the Texas coast. (AP Photo/Pat Sullivan)

HOUSTON (AP) — The heavy rains that caused major flooding along several Texas rivers over the past several weeks are fueling the creation of a new “dead zone” in the Gulf of Mexico and soon could lead to significant problems for marine life and commercial fishing, a Texas A&M University oceanographer said Thursday.

“Dead zones” are formed when freshwater empties into the salty waters of the Gulf, causing oxygen levels to drop and depriving marine life of oxygen.

“When this happens, the coastal waters become stratified, meaning that the lighter freshwater will stay at the surface and cap the saltier, and heavier, ocean water beneath,” Steve DiMarco, a Texas A&M scientist who’s researched the phenomenon for more than a decade, said.

“That is exactly what is going on right now and in the weeks to come, and when this happens, it almost always means many marine organisms, particularly those that live near and at the ocean bottom, can’t get enough oxygen and they can get sick and die.”

Scientists for years have monitored a dead zone off the coast of Louisiana caused by waters of the Mississippi River and the Atchafalaya River, which branches off from the Mississippi.

DiMarco said, similarly, that the Brazos, Trinity, Colorado and other rain-swollen Texas rivers now are carrying record amounts of freshwater south to the Gulf.

“There are no reports of fish kill yet,” he said. “We’re still fairly early in the process here.”

But he said buoys in the Gulf used for oil spill responses also register salinity “and they’re registering very low right now.”

A similar situation in 2007 left dead fish on jetties near Freeport, where the Brazos River enters the Gulf.

The oxygen deprivation phenomenon, known as hypoxia, also is a product of timing.

“If this flooding happens in February, we don’t care because fronts come through Texas all the time in winter,” DiMarco said. “And the wind energy is enough to break down the capping of the freshwater.

“Right now, the conditions are good for it. It’s summer time. There’s low wind. There’s high stratification because of all that freshwater coming out. There’s lots of heat. All those things are conducive to producing low oxygen in the bottom of the water.”

Copyright 2015 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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