The complexity of a food web — relationships among species and what they eat — is a key indicator of ecosystem health. Climate change may tip this delicate balance.

Chad Brassil, an assistant professor of biological sciences, is using mathematical models to study how duckweed populations respond to temperature fluctuations. His research may help scientists better predict how more frequent, intense storms and droughts affect food webs.

Duckweed plants are the size of a pencil eraser and float on ponds and marshes. These tiny plants are an important component in the wildlife food chain. Brassil is testing theories that temperature variations reduce indirect ecosystem interactions, the relationships involving species connected through an intermediate species. These dynamics are harder to study than direct relationships between species and prey, but are vital to an ecosystem.

Brassil earned a five-year, $531,141 Faculty Early Career Development Program award from the National Science Foundation for this research. This is NSF’s most prestigious award for outstanding pre-tenure faculty and supports their development as researchers and teacher-scholars.

Brassil said his method of using real organisms and abstract mathematical models is unique. Many researchers have developed mathematical models to predict changes in mean temperature over the next century, but few of those theories have been tested experimentally. And most researchers investigate general warming or cooling trends, not accounting for the fluctuations that extreme weather events cause.

Brassil’s Manter Hall laboratory is lined with floor-to-ceiling shelves that hold 14-gallon storage tubs. Inside, glass chambers house duckweed and aphid ecosystems plucked from wetlands near Lincoln. The aphids feed on duckweed. In the wild, aphids would then become food for other creatures. Duckweed is an ideal organism to study in food webs, Brassil said, because it propagates in less than one week.

Once the food webs are established, Brassil varies the ecosystems’ temperatures according to mathematical predictions about what could happen under various climate change scenarios.

“We need to know whether current mathematical theories are relevant in real-world situations,” Brassil said. “The challenge will be to extrapolate today’s findings and predict how ecosystems might respond 50 or 100 years from now.”

Brassil’s CAREER award also supports an outreach program between UNL and Lincoln Public Schools elementary classrooms. LPS students conduct basic duckweed experiments developed by a UNL elementary education major. Students in one of Brassil’s classes, Biology 207: Ecology and Evolution, also study duckweed. The students’ findings, whether simple or sophisticated, will be put in a database built by UNL computer science and engineering students and used to inform Brassil’s research.

“We know the hands-on approach is what gets kids excited about science,” Brassil said. “This is an opportunity for them to see their work published in a real, peer-reviewed scientific paper.”

– By Ashley Washburn, Research