Top Paper in Environmental Science: Leaving a legacy of dead zones

By Erika Engelhaupt
March 10, 2009; Environmental Science and Technology Environmental News

Copyright © 2009 American Chemical Society
“Gulf of Mexico Hypoxia: Alternate States and a Legacy” by R. Eugene Turner and Dubravko Justic, Louisiana State University; and Nancy N. Rabalais, Louisiana Universities Marine Consortium, 2008, 42 (7), 2323−2327; DOI 10.1021/es071617k.
In 1974, biologist R. Eugene (Gene) Turner was tossing about in a tiny 15-foot boat off the Louisiana shore when his handheld oxygen meter started showing strangely low readings. Turner was scouting the coastal waters as a new faculty member at Louisiana State University, and what he discovered led to a career-spanning quest to understand low-oxygen “dead zones”, or hypoxia, in the Gulf of Mexico. His longtime collaboration with coauthors Nancy N. Rabalais and Dubravko Justic (affectionately dubbed “Dubi” by his teammates) has now resulted in ES&T’s top science paper of 2008.
“Other people had measured low oxygen before, but it had never been followed up,” Turner says. He initially wondered if the low-oxygen areas were related to the large number of oil and gas rigs nearby, but soon he realized that high levels of nutrients flowing down the Mississippi River to the Gulf of Mexico were to blame. Most of the nutrients come from fertilizers used in the Midwest, and these nutrients stimulate excessive growth of algae that later rob waters of oxygen when they die and decompose.
In 1985, Turner and Rabalais received a small grant to map hypoxic zones. Rabalais then had her own turn bobbing about 25 miles offshore in an undersized Boston Whaler with a handheld oxygen meter. “I came back and told him I wasn’t going to die doing this research,” she says. For more than 20 years since then (and in successively larger boats), the now husband-and-wife team of Turner and Rabalais has surveyed hypoxia in the Gulf, with only one exception in 1989 when funding ran dry.
This year’s award-winning paper is a culmination of research that led the team to conclude that coastal ecosystems in the Gulf are becoming more sensitive to nutrient loads. “It’s not the same system as in the 1960s. It’s taking less nutrients now to fuel this hypoxic situation,” Rabalais says.
Over time, large nutrient-fueled algal blooms have deposited loads of organic matter to coastal sediments, and the slow decay of these remnants in the sediments continues to use oxygen. This extra demand for oxygen adds to the problem created by each year’s new blooms, and as a result, the potential size of the hypoxic zone doubled for a given nitrogen load from 1980 to 2000.
Michelle Scherer of the University of Iowa, a new ES&T associate editor, was impressed by the paper. “I was struck by what an excellent example of creative yet rigorous exploratory data analysis it was,” she says. “This ecosystem change or ‘alternate state’, as the authors define it, has serious implications for our efforts to reduce the extent of the dead zone. Unfortunately, it means we are going to have to work even harder than we expected.”
Turner cites Rabalais’s careful and persistent measurements as a key to their success. “It’s a remarkable accomplishment to do this year after year,” he notes. But Rabalais insists, “Gene’s the genius. He thinks systemwide.” Through years of up-and-down funding, “I’ve just been persistent,” Rabalais says. “I’m not sure if luck has been on our side, but the importance of ecological research has been on our side.”

(Left to right) R. Eugene Turner, Dubravko Justic, and Nancy Rabalais.