Gulf of Mexico ‘dead zone’ larger than normal, NOAA says

The National Oceanic and Atmospheric Administration (NOAA) is warning that the Gulf of Mexico’s “dead zone” is larger than average, with about 4 million acres of water potentially uninhabitable to fish and other marine life. 

The agency said in a Tuesday report that for the past five years, the average hypoxic zone, or area with little to no oxygen where marine life easily dies, has been 5,380 square miles. 

In 2021, this area is about 6,334 square miles, about 2.8 times larger than the 2035 target set by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, better known as the Hypoxia Task Force. 

The area is also larger than the 4,880 square miles NOAA had predicted in June based on Mississippi River discharge and nutrient runoff data from the U.S. Geological Survey. 

NOAA said Tuesday that the larger-than-normal dead zone could have been partially caused by high freshwater runoff from the Mississippi River, which measured above normal for three weeks prior to the agency’s cruise to measure the zone area. 

“Each year, excess nutrients from cities, farms and other sources in upland watersheds drain into the Gulf and stimulate algal growth during the spring and summer,” NOAA explained in its report. “The algae eventually die, sink and decompose.” 

“Throughout this process, oxygen-consuming bacteria decay the algae,” the report continued. “The resulting low oxygen levels near the bottom are insufficient to support most marine life, rendering the habitat unusable and forcing species to move to other areas to survive.” 

Nicole LeBoeuf, the assistant administrator for NOAA’s National Ocean Service, said in a statement, “NOAA and its partners use data from this cruise to help refine models and more accurately simulate how river discharge, nutrient loads, and oceanographic conditions influence hypoxic conditions in the Gulf and affect living resources.” 

“By understanding the scale and effects of these hypoxia events, we can better inform the best strategies to reduce its size and minimize impacts to our coastal resources and economy,” she added. 

The Environmental Protection Agency’s assistant administrator for water, Radhika Fox, said that studies into the hypoxic zone should take into account the continued impacts of climate change. 

“This year, we have seen again and again the profound effect that climate change has on our communities — from historic drought in the west to flooding events,” Fox said in a statement. “Climate is directly linked to water, including the flow of nutrient pollution into the Gulf of Mexico.” 

“As we work to address the Gulf of Mexico hypoxic zone, we must consider climate change and we must strengthen our collaboration and partnerships to make needed progress,” she added.