Shark attacks linked to the 'dead zone'

HOUSTON, Texas — The "dead zone" in the Gulf of Mexico this past summer covered approximately 5,800 square miles, forcing many aquatic species to flee or perish and others to attack.

"Fish and swimming crabs escape," said Nancy Rabalais, a scientist who has been studying the zone for years. "Anything else dies."

In a unique twist this year, this large area of water devoid of oxygen could also be contributing to shark attacks along the Texas Gulf Coast. As of early August, three people had been bitten. That might not seem like a high number, but only 18 shark attacks have been recorded in this area since 1980.

In recent years, increasing numbers of sharks have been seen inshore along the Texas-Louisiana border, said Terry Stelly, an ecosystem biologist with the Texas Parks and Wildlife Department.

He theorized that these predators might be looking for higher dissolved oxygen content.

Rabalais agreed.

"The higher number of sharks in shallow waters may very likely be due to the low oxygen being close to the shore at the time of the attacks," she said. "The available habitat for the sharks is definitely less when the low oxygen is so widespread."

During the past 30 years, the dead zone has been an annual phenomenon, spreading westward from the mouth of the Mississippi River, as algae bloom and die, burning up oxygen in the near-shore waters. Scientists believe that fertilizers and animal wastes draining into the river throughout its watershed are primarily to blame for this environmental destruction. But farmlands of the upper Midwest are viewed as the primary contributors.

Even though the source of the problem has been identified, little has been done to stop this nutrient overload, which continues to destroy not only the Gulf of Mexico, but the nation's most famous river. 

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