Gulf of Mexico ‘Dead Zone’ Nearly the Size of Connecticut

American white pelicans in the Gulf of Mexico. (Photo by U.S. Fish and Wildlife Service)

(CN) – The northern Gulf of Mexico’s “dead zone” area with little to no oxygen will become larger than the state of Connecticut by the end of July, according to a study published Thursday.

The findings suggest the dead zone will cover roughly 6,620 square miles of the bottom of the continental shelf off Texas and Louisiana. Of the 500 dead zones in the world, the area in the northern Gulf of Mexico is the second largest human-caused coastal hypoxic area – a zone in the ocean with a concentration of oxygen low enough to suffocate and kill nearby animal life – on Earth.

While the forecast is within the average size of the dead zone over the past 31 years, it is about 3.5 times larger than the Hypoxia Action Plan’s goal of limiting the area to about 1,930 square miles. Efforts to decrease nitrate loading have yet to demonstrate success at the watershed scale.

Each year, Louisiana State University and Louisiana Universities Marine Consortium scientists Nancy Rabalais and Eugene Turner conduct a research cruise to measure the dead zone, which has little or no oxygen in the bottom tiers. The pair then plugged these data into their computer models to forecast its size in the summer.

“The oceans warm a little more each year and currents change, making new observations a necessity,” Turner said. “Model calibration is not a fixed phenomenon.”

Nutrients from the Mississippi River watershed, particularly phosphorus and nitrogen, fertilize the Gulf of Mexico’s surface layers to create excessive levels of algae. When the algae decompose in the deepest portions of the ocean, they foster oxygen distress and can even kill organisms in the gulf’s richest waters.

These low-oxygen conditions threaten living resources like fish, crabs and shrimp, which humans depend on for industry and food.

“This means that the impacts of water quality changes upstream in the Midwest affect our coast – directly,” Rabalais said.

While the dead zone occurs year-round, it is most steady and severe in spring and summer.

Multiple computer models use the May nitrogen load of the Mississippi River as the primary driving force to predict the size of the gulf’s dead zone in late July. A storm could reduce the span of the dead zone to 6,316 square miles.

The National Oceanic and Atmospheric Administration uses the results from the LSU scientists’ computer models as well as several other models to generate its forecast, which is about 5,780 square miles.

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