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Gulf ‘Dead Zone’ area smaller this year

Posted Aug. 7, 2013

The Louisiana Universities’ Marine Consortium (LUMCON) reported July 28 that its 2013 survey of the so-called “Dead Zone” in the Gulf of Mexico shows that the area is smaller than expected this year.

The 2013 area of low oxygen measured 5,800 square miles in this summer’s mapping expedition, according to a LUMCON release. The researches predicted the area to be 7,300 to 8,600 square miles based on the May nitrogen load from the Mississippi River.

“While not one of the larger areas mapped since systematic surveys started in 1985 by LUMCON and Louisiana State University researchers, the size of this year’s zone of oxygen-depleted bottom-water is above the long-term average and above the average size of the last five years,” the release stated.

The researchers say Hypoxia forms as a result of the nutrient-overloaded waters of the Mississippi River stimulating the excess growth of phytoplankton. Not all of the phytoplankton is consumed by higher levels of the food web, and it sinks to the seabed where bacteria decompose the remains and deplete the oxygen. The low oxygen forms in the lower half of a stratified water column (warmer, fresher water overlying cooler, saltier water), which keeps the plentiful oxygen in the surface waters from reaching into the lower layer and replenishing the oxygen depleted by the microbial activity.

The Iowa Department of Agriculture and Land Stewardship, Iowa Department of Natural Resources and Iowa State University are taking a science and technology-based approach to assess and reduce nutrients delivered to Iowa waterways and the Gulf of Mexico.

The Iowa Nutrient Reduction Strategy has been developed to direct efforts to reduce nutrients in surface water from both point sources, such as wastewater treatment plants and industrial facilities, and non-point sources, including farm fields and urban areas, in a scientific, reasonable and cost-effective manner.

The Iowa strategy has been developed in response to the 2008 Gulf Hypoxia Action Plan that calls for the 12 states along the Mississippi River to develop strategies to reduce nutrient loading to the Gulf of Mexico. The strategy will be used to develop operational plans through the Water Resources Coordinating Council. It is designed to be a dynamic document that will evolve over time as new information, data and science is discovered and adopted.

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