‘Dead Zone’ Researchers Complete 35th Gulf of Mexico Research Cruise

LSU researchers completed their 35th research cruise this year to collect data on the “Dead Zone” in the northern Gulf of Mexico. LSU Department of Oceanography & Coastal Sciences Professor Nancy Rabalais led a research team that mapped the bottom area of low oxygen in Louisiana coastal waters west of the Mississippi River, which is commonly known as the “Dead Zone,” from July 25 – July 31. LSU Department of Oceanography & Coastal Sciences Assistant Professor Cassandra Glaspie joined the research team as co-chief scientist. The data the team collected suggest that the zone is 6,334 square miles, or 16,400 square kilometers. This is larger than the 4,760 square miles, or 12,330 square kilometers, the researchers had forecasted based on river discharge and nutrient loads in May.

The somewhat higher than average river discharges from the Mississippi River and the Atchafalaya River in July provided more fresh water to the northern Gulf of Mexico, which contributed to more algae, more sinking carbon and more bacterial respiration reducing the dissolved oxygen. This is the 16th largest hypoxic, or low-oxygen zone recorded by the researchers. 

“This year’s hypoxic zone estimate comes after 35 years of conducting the summer research cruise, and many other cruises, to define oxygen depletion in the northern Gulf of Mexico. The value of the unique long-term data is the ability to use it to better understand the system, support complex models and address management concerns about Mississippi River water quality and its impact in the nearshore coastal waters,” Rabalais said.

The low oxygen conditions in the Gulf of Mexico’s most productive waters stress organisms, threatening living resources, including fish, shrimp and crabs, and may even kill them. Low oxygen conditions started to appear 50 years ago when agricultural practices intensified in the Midwest. 

The nitrogen loading of the Mississippi River to offshore remains high. There are efforts by states along the main stem and others in the watershed to reach lower loads of excess nutrients through the Mississippi River/Gulf of Mexico Hypoxia Task Force https://www.epa.gov/ms-htf and others. 

“The efforts need to continue and intensify as we face many societal and environmental knowns and unknowns in both the watershed and in offshore waters. We, as citizens of the watershed, need to lessen our consumption of nitrogen-based products and reduce other activities that contribute reactive-Nitrogen to the environment,” write the researchers.

“Thirty-five years and continuing. It isn’t going away but getting larger for the same amount of nitrate loading. It is both a pivotal change for the continental shelf off Louisiana, and another indicator, among many, of humans compromising the Earth’s finitudes. Where is our moral and ethical compass? As the character Pogo said in the comic strip written for the first Earth Day: ‘We have met the enemy and he is us,’” said Gulf of Mexico researcher and LSU Boyd Professor Gene Turner.