Louisiana News

Scientists find smaller ‘dead zone’ in the Gulf than initially expected this summer

WWNO - New Orleans Public Radio | By Héctor Alejandro Arzate (Mississippi River Basin Ag & Water Desk)

Published August 13, 2026 at 4:43 PM CDT

Measuring a 'dead zone': Scientists retrieve the CTD (conductivity, temperature, depth) package of ocean sensors after profiling dissolved oxygen at a station during the Shelfwide Hypoxia Cruise in the Gulf of Mexico in July 2026.

Scientists on board a research vessel have found a smaller “dead zone” in the Gulf of Mexico than initially expected this summer.

At approximately 1,332 square miles, the zone is the second-smallest measurement in 40 years of measurement, according to researchers backed by the National Oceanic and Atmospheric Administration.

The dead zone is a region of the Gulf that emerges each summer where there is not enough oxygen to support fish and marine life, a condition known as “hypoxia.” In June, NOAA had forecast a dead zone that would have covered more than 7,000 square miles — or nearly the size of New Jersey. That would have been larger than the four-decade average of 5,200 square miles.

However, the winds and waves caused by Tropical Storm Bertha in late July led to high-oxygen water being mixed into the water column. That is what was measured during the annual cruise led by scientists at Louisiana State University and the Louisiana Universities Marine Consortium.

Top figure: A map of the measured Gulf of America hypoxia zone, July 24-30, 2026. Red area denotes 2 mg/L of oxygen or lower, the level which is considered hypoxic (i.e., having inadequate oxygen levels) at the bottom of the seafloor. (Bottom) Long-term measurement of the Gulf hypoxic zone (green bars) as found during ship surveys conducted since 1985, including the target goal established by the Mississippi River/Gulf of America Hypoxia Task Force and the 5-year average size (black dashed lines).

That research, which receives support from NOAA, as well as federal partnerships with many basin states, is part of the ongoing efforts of the Mississippi River/Gulf of America Hypoxia Task Force. It has a long-term goal of reducing the dead zone to less than 1,900 square miles by 2035.

The task force works with stakeholders in both the agriculture and wastewater industry to reduce the amount of nitrogen and phosphorus pollution, which is largely responsible for the dead zone. In June, the group announced that it had reached an interim goal of shrinking the zone by 20%.

“While weather and river flow will always influence year-to-year results, the data shows that our collective efforts are making a difference,” said Mike Naig, the secretary of agriculture in Iowa, in a press release issued at the time.

Although the size of the dead zone this year hits close to the overall goal, the official report from researchers in Louisiana noted that it represents “physical mixing” of the water column. Previously, researchers have urged the importance of the “trend over time.”

Scientists from Louisiana State University and the Louisiana Universities Marine Consortium (LUMCON) aboard the Research Vessel Pelican are collecting data to measure the size of the Gulf's dead zone in the summer of 2024. The results found the dead zone, a low-oxygen area caused primarily by the over-application of synthetic fertilizer on Midwest farms, was approximately 6,705 square miles. In order to survive, fish, shrimp, and other species need to flee an area the size of New Jersey.

Coastal Desk

The True Cost of Fertilizer

Carlyle Calhoun, Garrett Hazelwood (Floodlight News), Eric Schimd

This is the story of modern fertilizer, and how this powerful concoction of chemicals has radically reshaped how we farm and what we eat. In this episode, we follow the journey of fertilizer from Louisiana to the Midwest, then back down along the Mississippi River to a place it creates in the Gulf. A place called: The Dead Zone.

Officials at NOAA said the annual measurement is “more than just a scorecard.”

“It helps us better understand the interconnectivity of our nation’s land, waterways, and ocean,” said Timothy Petty, NOAA’s assistant secretary of commerce for oceans and atmosphere, in a press release.

Despite some progress, stakeholders and researchers alike have been calling on Congress to continue funding hypoxia reduction strategies. Last December, more than 60 groups in agriculture and conservation signed onto a letter organized by the Upper Mississippi River Basin Association.

“There’s a lot of groups that you might view as opposing or conflicting that have joined together to work with states in their nutrient reduction strategies,” said Kirsten Wallace, the executive director of UMRBA. “These are consensus-based solutions that do make a difference.”

This story is a product of the Mississippi River Basin Ag & Water Desk, an independent reporting network based at the University of Missouri in partnership with Report for America, with major funding from the Walton Family Foundation.