Caption: (Top) Map of measured Gulf hypoxia zone, July 21 - July 26, 2024. Red area denotes 2 mg/L of oxygen or lower, the level which is considered hypoxic, at the bottom of the seafloor. (Bottom) Long-term measured size of the hypoxic zone (green bars) measured during the ship surveys since 1985, including the target goal established by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force and the 5-year average measured size (black dashed lines). (Image credit: LUMCON/LSU/NOAA)

NCCOS-supported scientists have determined that this year’s Gulf of Mexico “dead zone” — an area of low oxygen that can kill fish and marine life — is approximately 6,705 square miles, equivalent to more than four million acres of habitat potentially unavailable to fish and bottom species.

This measurement brings the five-year average to 4,298 square miles, which is more than two times larger than the 2035 target set by the Mississippi River/Gulf of Mexico Hypoxia Task Force (HTF). The annual dead zone survey was led by scientists at Louisiana State University and the Louisiana Universities Marine Consortium (LUMCON) during a research cruise from July 21 - July 26 aboard the LUMCON R/V Pelican.

In June 2024, NOAA forecasted a above-average sized hypoxic zone of 5,827 square miles (the record of 8,776 square miles was set in 2017). While the model results underestimated the measured size of the zone this year, they were within the expected margin of uncertainty for the forecast and provide further evidence of the robustness of the models to relate nutrient inputs to observed hypoxia size in the summer.

The HTF uses the annual hypoxic zone size determination as a key metric to measure progress toward achieving the five-year average target of 1,900 square miles or smaller by 2035. Maintaining ongoing summer surveys and calculating a five-year average allows scientists to capture the true dynamic nature of the zone more than a single annual measurement. 

In addition to its annual hypoxia forecast and survey, NOAA supports efforts to develop monitoring technologies to understand the dead zone, as well as to study the impacts of hypoxia on fish and fisheries in the Gulf of Mexico and elsewhere through its Coastal Hypoxia Research, Ocean Technology Transition, Uncrewed Systems and Hypoxia Watch programs. The agency continues to partner with states to develop new tools to predict nutrient runoff to waterways and to support the Northern Gulf Institute to deliver technical assistance, observation and monitoring capabilities.  

NOAA scientists are also investigating the feasibility of using autonomous surface vehicles (ASVs) as an emerging technology to map hypoxia in the Gulf of Mexico. This year, several ASVs were deployed in coordination with the measurement survey, which will be compared with  the ship-based measurements.

For more information about the 2024 Gulf of Mexico dead zone, view the NOAA Press Release or watch this Ocean Today video.