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Gulf of Mexico ‘Dead Zone’ Is Shrinking


Scientists with the National Oceanic and Atmospheric Administration have discovered changes within the Gulf of Mexico hypoxic zones.

Every year during the summer, several marine species in the Gulf of Mexico die after being exposed to a dead zone, an overgrowth of algae and excess nutrients that create a lack of oxygen.

Some species manage to escape, but animals that are unable to relocate sink to the bottom of the ocean.

National Oceanic and Atmospheric Administration scientists are forecasting that this summer’s dead zone will be roughly 4,880 square miles.

That’s compared to 2,116 square miles in 2020, but still almost half of the largest dead zone ever, 8,776 square miles in 2017.

Last year’s figure was the third smallest dead zone in the 30-plus years of measuring. Similar to 2018 and 2019, a storm — in this case, Hurricane Hanna — had the power to “mix” ocean water and disrupt the hypoxic zone.

“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. We really try to look at the long term trends," NOAA’s David Kidwell said last year.

Hypoxia Land Use with Legend (2) (1).png
The Mississippi River near Vicksburg, Mississippi, looking northeast at the I-20 bridge in October 2016. NOAA figures show the amount of nitrates and phosphorous discharged from the Mississippi and the Atchafalaya rivers were much lower than the forty-year annual average.

This year’s estimate is slightly lower than the five-year average that NOAA scientists emphasize — approximately 5,400 square miles.

“Understanding the effects of hypoxia on valuable Gulf of Mexico resources has been a long- term focus of NOAA’s research,” Nicole LeBoeuf, acting director of NOAA’s National Ocean Service, said in a press release.

River discharge that takes place in the month of May is known to affect the size of the hypoxic zone that appears each summer.

Carica Astrel is a WUSF/USF Zimmerman School digital news intern for the summer of 2021.