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| Best of NAMA 2026 |
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GULF HYPOXIA HITS 40-YEAR LOW
Sep. 8, 2026
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| Farm Progress | | Better farming practices in the Midwest and throughout the Mississippi River basin have contributed to improving the picture of the hypoxic zone in the Gulf of Mexico. |
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| Warren Formo |
by Warren Formo is executive director of the Minnesota Agricultural Water Resource Center as it appeared in Farm Progress' The Farmer magazine
Editor's Note: With a heavy heart, we are relaying the news that Warren Formo passed away peacefully in his sleep Aug. 29. More details will follow.
In August, the National Oceanic and Atmospheric Administration (NOAA) announced that the Gulf Hypoxic Zone measured this summer is the second smallest on record in 40 years of measurement.
The zone measured 1,332 square miles, which is significantly lower than the 2035 goal of 1,900 square miles as a five-year average. The five-year average size of the hypoxic zone now stands at 3,745 square miles.
Earlier this year, I reported on a report from EPA on nutrient reduction efforts relating to the Gulf Hypoxia Action Plan, highlighting improvements in nitrogen and phosphorus management throughout the Mississippi River Basin. To read that report click here.
Hypoxia is a condition where oxygen levels in the water decline to less than 2 milligrams per liter, which can affect fish and other aquatic life. This low-oxygen condition occurs seasonally, usually peaking in late July. The Gulf Hypoxic Zone forms when algae grow rapidly in early summer, fueled by nutrients delivered to the Gulf of Mexico through the Mississippi River. In late summer, the algae die and decompose, which removes oxygen from the water.
In June, NOAA predicted a hypoxic zone of over 7,000 square miles. This is based on models linking Mississippi River water and nutrient levels and assuming "typical weather conditions." NOAA's press release notes that tropical storm-force winds in the days preceding their measurement cruise churned the water, mixing oxygen-rich surface waters with bottom waters, seemingly implying that their measurement did not capture the full extent of the hypoxic zone.
Gulf hypoxia is a very complicated topic. The extent of mixing or layering of lighter fresh water from the Mississippi River on top of heavier saltwater plays a big role in the size of the zone. The very reason that the hypoxic zone survey takes place annually during the last week of July is that that is when it is expected to be its largest. During much of the year, the hypoxic zone may not even exist.
So regardless of whether or not the weather around the time of the measurement is "typical" or "normal," the measured zone is what it is. In the past decade, the measured late-summer size of the hypoxic zone has ranged from almost 9,000 square miles to this year's low of 1,332 square miles. In those years are a mix of dry years and wet years, "normal" weather and not-so-normal weather.
This year's measured hypoxic zone makes a significant step toward the long-term goal, reducing the five-year average by nearly 25%. This suggests that nutrient reduction actions, including better farming practices, are making a difference.
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