'Water webs' attract students to ASU study


Margaret Coulombe

An article published in the Sierra Vista Herald by Associated Press reporter Dana Cole examines research being done by ASU School of Life Sciences scientists and their students based out of the Grey Hawk Nature Center. John Sabo, associate professor, and C. Jaco Klok, a postdoctoral researcher, their colleagues and ASU students are looking at the physiology of crickets, lizards and spiders, and the relationships between wildlife and the San Pedro River, to get a better understanding of “groundwater’s influence on food chain systems in desert riparian regions.”

Their studies also partner ASU graduate students in the College of Liberal Arts and Sciences and hands-on research projects with middle school children at the nature center.  

“We want to see how the water flows from the river and groundwater through plants, with animals feeding on the plants and animals feeding on animals,” Klok says. One technique discussed in the report involves the injection of stable isotopes of hydrogen and oxygen, with measurements taken at different intervals to determine the rates of water depletion and energy use.

Cole’s piece goes on to explain that “because of the seasonal nature of the river’s flow, water is not always available for animals to drink directly. So some animals derive their water from food.” 

That is to say: spiders eat crickets, and crickets eat green cottonwood leaves for water, not nutrients. This cascade was discovered and coined a “water web,” to distinguish it from the classical food web, by Kevin McCluney, former ASU doctoral student in the Sabo laboratory.

Klok notes in the article that “disrupting the waterway would have consequences that not only result in the collapse of the ecosystem here, but would be as far-reaching as the end destinations of migrating birds.” Klok warned: “It’s is not only a local problem, but involves the waterway’s end destinations. This project is basically trying to quantify all of the ins and outs of the water web.”

School of Life Sciences faculty members Sabo, Juliet Stromberg and Nancy Grimm have been awarded $1.3 million in grants in 2010 from the U.S. Department of Defense and the National Science Foundation. Their research projects focus on the critical gap between studies of ground water, hydrology and energy in food web ecology in terrestrial systems, as well as the impacts of climactic variability, flash floods and droughts in stream ecosystem structure.

Cole’s piece about ASU activities in the Herald generated interest locally, through media outlets like Tri Valley Central and Casa Grande Dispatch, and as far away as Georgia and Connecticut from July 4 -14, 2010.

To read more about water webs: learn more about riparian systems and Sabo’s research, go to his Science Studio audioprogam, Vol 7: