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Gulf "dead zone" predicted to be largest ever recorded

Image from Louisiana University Marine Consortium Image from Louisiana University Marine Consortium

Cocodrie, La. - Each summer, massive areas of the usually fertile Gulf of Mexico fishing grounds become uninhabitable to most sea life. FOX 8 spoke with a scientist who says this year the "dead zone" may be the largest since monitoring began in 1985.

The Mississippi River is known as America's great byway, carrying goods from the heartland to the world and back. But much more lurks in the muddy waters rolling through this beautiful crescent.

Nancy Rabalais is the director of Louisiana University Marine Consortium. She said, "It's an annual cycle with nutrients and fresh water delivered from the Mississippi River. The fresh water creates a two-layer system offshore and the nutrients stimulate the growth of the single celled phytoplankton."

The fertilizers that help grow food also feed single-cell organisms that thrive in the summer heat. Rabalais said, "At least 50 percent of the nitrogen comes from row crops such as corn and soybean."

In many ways the nutrient-filled Mississippi River is the reason for Louisiana's rich fishing grounds. But scientists say the water can hold too much of a good thing.

"The plankton bloom at such a high rate because of so many nutrients that a lot of it can't be used by the food web so it sinks to the bottom. On the bottom bacteria decomposes it and uses up the oxygen and because of that two-layer system. Oxygen from the surface waters can't get to the bottom to replenish what's being consumed by the bacteria. So we end up with a large area of low oxygen across the Louisiana shelf," Rabalais explains.

Farmland lines the Mississippi and its tributaries. Rabalais said, "If Louisiana had to actually pay to clean up the water before it got into the Gulf of Mexico, they would definitely be pointing the finger at Arkansas, Missouri, Tennessee, Ohio, other places up north. But right now there's no cost to polluting the waters, so the incentives are not particularly there for people to make a difference."

This year the dead zone is expected to be larger than ever recorded. According to Rabalais, "It's predicted to be as large as or slightly larger than the largest size we've documented to date."

The area will be useless to fisherman and expected to rival the size of New Jersey. Rabalais said, "It does lead to reduced catches and the fact that the low oxygen is there also prevents the shrimp from migrating to further offshore to grow to a larger size. That would definitely be more beneficial to the fishery than the small size if they are caught in near-shore waters."

In July the research team will cruise the Gulf, taking oxygen samples in more than 100 locations to get a good reading on the actual size of this year's dead zone or hypoxic zone -- the scientific definition of the water with very low oxygen readings.

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