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A lifetime of research links Gulf of Mexico ‘dead zone’ to Midwest fertilizer runoff [1]

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Date: 2023-06-08  

This is the first in a series.

In the summer of 1985, Nancy Rabalais set sail on a research vessel into the Gulf of Mexico — and into the scientific unknown.

Back then, scientists knew little about wide expanses of low-oxygen water, called hypoxia, that sometimes appeared in the Gulf and other bays and rivers. That summer, Rabalais’ team was set on discovering how these areas connected to creatures that dwell on the bottom of the Gulf.

While analyzing water and sediment samples miles off the coast, the team from the Louisiana Universities Marine Consortium and Louisiana State University quickly discovered that hypoxia stretched from the Mississippi River to Texas and lasted for most of the summer.

Later, they pinpointed the cause: increased amounts of nitrogen and phosphorus in the Gulf, largely due to runoff from farm fertilizer and other sources in the Mississippi River basin.

Rabalais’ research put the Gulf of Mexico “dead zone” on the scientific map and into the nation’s psyche, leading to the creation of the U.S. Environmental Protection Agency’s Mississippi River/Gulf of Mexico Hypoxia Task Force and a host of efforts to combat nutrient pollution, which EPA calls “one of America’s most widespread, costly and challenging environmental problems.”

Over nearly four decades, Rabalais has become a giant in her field — testifying to Congress multiple times, mentoring countless students at LSU and publishing roughly 160 studies.

Now 73, Rabalais said she doesn’t plan to go on the research cruises anymore due to her age and health issues. But she remains engaged in her work and is training the next generation.

“I believe in doing research that can support the public good,” she said. “This is one of those ways.”

The early days

Born in Wichita Falls, Texas, Rabalais grew up with a love for water. She was certified to scuba dive at the age of 19, a skill that would come in handy while replacing monitors 60 feet under the Gulf surface.

She was fresh off a doctorate in zoology with a minor in marine science from the University of Texas at Austin when she took charge of LUMCON’s first hypoxia research cruise in the Gulf of Mexico in 1985, directing a full-time crew on the 116-foot long research vessel Pelican.

“I just developed enormous respect for her, not only in terms of her commitment and intelligence, but her fortitude,” said Don Boesch, the first executive director of LUMCON.

The crew set out from Terrebonne Bay and traveled about six to eight hours to reach the dead zone, where they took oxygen measurements at established stations. This network eventually grew from roughly 40 to 80 stations, spanning the coast from Louisiana to Texas.

Nancy Rabalais with scuba gear on around 2015. (Photo courtesy of Nancy Rabalais)

Rabalais and her colleagues also dug into the history of nutrients, literally. By inserting tubes into mud from the bottom of the Gulf and slicing them up, they were able to date the different layers of sediment and identify amounts of carbon and nitrogen from decades earlier. That proved the Gulf had not always been low in oxygen.

“We did all kinds of things to piece together the story and develop the long-term dataset,” Rabalais said.

A life of hypoxia research

Over time, the crew grew to include professors, scientists, students and volunteers from a variety of disciplines. One was fellow oceanographer Eugene Turner, now a professor at LSU. A mainstay in hypoxia research from the beginning, he also became Rabalais’ partner, and they married in 1988. Together, they worked to detail the causes and effects of hypoxia in the Gulf.

By 1998, Rabalais was testifying before congressional committees to tell legislators why they should be concerned about hypoxia. As a result, Congress decided that federal funds should be given each year to the National Oceanic and Atmospheric Administration to mitigate hypoxia.

“When we started out, she’d laugh at me. She’d say ‘Oh, you’re going to write a paper and change policy?’” Turner said. “But that’s what we do.”

Rabalais became executive director of LUMCON in 2005 and maintained the position until 2016. Her research has documented most of what we now know about Gulf hypoxia.

Gulf’s dead zone caused by Midwest runoff

From about May to September every year, the Gulf develops the largest hypoxic zone in the U.S. Hypoxic conditions occur when an area of water has less than 2 milligrams of oxygen per liter of water. It usually means the death or flight of most living organisms in the area.

Hypoxia can occur naturally in water, but humans have worsened the problem since the 20th century. Nutrient runoff from farm fertilizer and other sources washes into rivers and streams, increasing nitrogen and phosphorus in waterways.

Nutrients from states and provinces in the Mississippi River basin wash into the watershed and into the Gulf in the spring and early summer. The freshwater with excess nutrients lies on top of the Gulf saltwater and spurs algal blooms. The algae eventually die and sink into the saltwater below, using up the oxygen supply.

Matt Rota, senior policy director for the advocacy group Healthy Gulf, said addressing nutrient pollution is important for everyone.

“The things that we’re doing to cause the dead zone are also causing us to have less healthy soil and causing our drinking and recreational waters to become polluted,” he said.

The hypoxic monster stretched across about 3,275 square miles of the Gulf in 2022. It was smaller than the previous year’s, mostly due to lower discharge from the Mississippi River. The area has trended mostly larger over time, with a five-year average size that’s still more than two times larger than the 2035 task force goal. This year’s annual forecast was due out Tuesday.

“We’re not on track,” Rabalais said regarding the goal. “I keep saying there’s no social will.”

Fertilizer and agribusiness

Since the 1950s, the amount of nitrogen in the Mississippi River watershed has tripled, and the amount of phosphorus has also increased, in part from fertilizer applied in Midwestern states.

Congress exempted agriculture from the Clean Water Act of 1972, leaving responsibility for controlling nutrient pollution to individual states. This restricts the EPA’s ability to limit nutrient runoff from non-point sources like farms. The result is multiple federal- and state-funded efforts to reduce nutrients through voluntary programs for farmers, like rotating crops to enrich the soil naturally without fertilizer.

But those efforts have not yet met goals to dramatically reduce the size of the dead zone. Some researchers and advocates argue the responsibility of reducing runoff should rest on the agriculture system, rather than on individual farmers who often have little incentive to adopt voluntary changes.

For Rabalais, persistence is the name of the game. She believes we shouldn’t discount the role of the individual — she eats less meat and avoids ethanol fuel to lessen her personal impact.

“I try to maintain my optimism that good efforts can produce good results.” she wrote in a 2021 reflection on her work.

Cassandra Glaspie and Nancy Rabalais share a laugh in a LUMCON lab in Cocodrie, La., Wednesday, March 15, 2023. (Photo by Lauren Whiddon/WUFT News)

A new era

As Rabalais ends her era at the helm of Gulf hypoxia research, she has been mentoring marine biologist Cassandra Glaspie to take the reins.

Glaspie studies benthic organisms, creatures that live in bottom waters. After finishing a postdoctoral program in Oregon studying hypoxia, Glaspie became a professor at LSU in the same department as Rabalais.

In addition to heading the annual research cruise and some related studies going forward, Glaspie is deciding what the future will hold for portions of Rabalais’ lab. She wants to expand and update monitoring efforts and create an internship for students from underrepresented groups, including farmers’ children.

But paying for future initiatives may be a challenge. NOAA provides funding for the research cruise to measure oxygen in the water, which maintains the dataset over time. But continuing long-term study of contributing factors like the distribution of nutrients requires additional funding, which Glaspie and Rabalais have been working toward securing.

The work is never finished, but Rabalais is hopeful for the future.

“I would like to see a healthy gulf,” she said. “We can never go back where we were, but we can make progress.”

This story is part of The Price of Plenty, a special project investigating fertilizer from the University of Florida College of Journalism and Communications and the University of Missouri School of Journalism, supported by the Pulitzer Center’s nationwide Connected Coastlines reporting initiative and distributed by the Mississippi River Basin Ag & Water Desk.

Type of work: News Service Produced externally by an organization we trust to adhere to journalistic standards.

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[1] Url: https://investigatemidwest.org/2023/06/08/a-lifetime-of-research-links-gulf-of-mexico-dead-zone-to-midwest-fertilizer-runoff/

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