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Gulf 'Dead Zone' Measurement Impeded By Hurricane Hanna

dead_zone_excursion_2020.jpg
National Oceanic and Atmospheric Administration

Scientists recently went on their annual excursion to the "dead zone" in the northern Gulf of Mexico, only to find that tropical weather disrupted the data.

Back in June, the National Oceanic and Atmospheric Administration, along with the U.S. Geological Survey, forecasted this year's Gulf dead zone to be larger than average, but last month, Hurricane Hanna swept through, making landfall off the southern coast of Texas.

David Kidwell with NOAA said the storm reintroduced oxygen to the dead zone, which scientists call the hypoxic zone.

"We ended up measuring a much smaller, in fact the third smallest hypoxic zone on record, as a result. But I will say this annual variability, this chance of storms coming through is why the efforts to manage and mitigate the hypoxic zone don't just focus on a single annual number to track progress,” he said. “We really try to look at the long term trends."

The five-year running average used by scientists now measures the dead zone at 5,408 square miles, said Kidwell. 

It was originally projected to be greater than average this summer around 6,700 square miles because large amounts of water and nutrients had been flowing into the Gulf from the Mississippi River Watershed.

dead_zone_graph.jpg
Credit National Oceanic and Atmospheric Administration

Kidwell said a big contributor to the lack of oxygen in the water is the amount of nutrients flowing in from agricultural lands.

"So even though each individual farm is contributing a relatively small amount of nutrients, that adds up over time. The cumulative toll, in terms of the role of those ag lands on nutrient additions to the Gulf of Mexico, is relatively substantial,” he said.

States have been working on conservation initiatives with the U.S. Department of Agriculture, said Kidwell, like keeping fertilizer on agricultural lands, or installing wetlands to naturally pull out those nutrients before they get into neighboring water bodies.

The Mississippi River/Gulf of Mexico Hypoxia Task Force, made of up of federal and state agencies along with the tribes, has a goal to decrease the dead zone to 1,900 square miles, said Kidwell.