Toxic to Tadpoles

When Rose Adelizzi ’19 sits down to explain her research project, her hands immediately start to fly just above the table in illustration of the shape of the small boxes used to conduct the experiments.

“We were looking at how multiple chemical contaminants act as stressors and can affect amphibian growth,” she explains.

Adelizzi, a double major in biology and environmental science with a minor in chemistry, was about to leave for Sacramento to present her research findings on the effects, separately and in combination, of herbicides, pesticides, fertilizers, and salt on the southern leopard frog (Lithobates sphenocepala). The project started in the summer of 2017 when she was awarded a grant from the John S. Toll Science and Mathematics Fellows Program to conduct a 10-week research project under the mentorship of Robin van Meter, assistant professor of environmental science/studies and biology. On this trip, she would be accompanied by van Meter and her classmate Julia Portmann ’19, co-authors on the presentation developed for the annual conference of the Society of Environmental Toxicology and Chemistry (SETAC), as well as a manuscript detailing their tadpole research, now in review with a scientific journal. Both Adelizzi and Portmann are members of the College’s Douglass Cater Society.

“It’s very relevant here on the Eastern Shore,” Adelizzi notes. “We did a little field work in the beginning when we collected southern leopard frog egg masses from the College’s River and Field Campus. We brought them back to campus and hatched them, raised them in the greenhouse at Toll Science Center, and then subjected them to the chemical treatments.”

Tadpoles exposed, for example, to atrazine—a herbicide widely used on crops and turf—showed a faster metamorphosis into the next phase of growth and, as Adelizzi says, “they were very stressed out, possibly indicating they were growing faster to try to get out of that situation.” That faster metamorphosis could negatively impact other characteristics, she says. “Maybe their immune systems were compromised or overall fitness or reproductive abilities were affected.”

Changes in tadpole growth were determined by surface area measurements taken from biweekly photographs analyzed with ImageJ software. As noted in their abstract, the combined chemical treatment of atrazine, salt, and nitrogen heightened stress levels prior to metamorphosis. By the end of larval development, tadpoles exposed to nitrogen had significantly larger surface area. As amphibians are exposed to multiple chemicals simultaneously in the environment, the young researchers say, assessing the effects of a combination of contaminants is necessary to improve application strategies and ecosystem health.

“The work that Rose and Julia have done in my lab, and the work that Rose continued over the summer of 2017 as a Toll Fellow, provide a critical evaluation of the effects of manmade pollutants on larval amphibians,” says van Meter. “While many studies have been published on the individual effects of pesticides, road salts, and fertilizers, their research is the first to combine all three chemicals, which represents a more realistic field scenario for amphibians in the wild. Rose and Julia’s research also used novel techniques, including the use of ImageJ software to get tadpole surface area measurements throughout larval development, and a waterborne assay for quantifying levels of stress hormones.”

Adelizzi, who helped van Meter adapt liver and brain tissue bioassays for juvenile amphibians after pesticide exposure, co-authored a manuscript with her faculty mentor that has been accepted for publication in Environmental Toxicology & Chemistry.