More and more each autumn, the leaves that fall into the cold, spring-fed ponds and stream at Carroll’s Greene Field Station are buckthorn, rather than the ash leaves of years past. The leaves disintegrate in the water and the decomposed bits are shredded and consumed by amphipods, tiny shrimp-like creatures which occupy the bottom of the food chain, and, thus, directly or indirectly, supply a lot of the other critters in and out of the water. For years, the amphipods thrived on ash leaves, but their diet is rapidly changing.
We know this, because of research that has been conducted out at Greene Field Station and Prairie Springs Environmental Education Center over the past several years by faculty and students. It matters because buckthorn is an invasive species. A European shrub, buckthorn leafs out earlier than native plants in the spring and holds onto its leaves later in the fall, giving it an advantage over the native species. Combine that with the emergence of the emerald ash borer, which has already killed or diseased four-fifths of the ash trees on the property, and the diet of the amphipods has undergone significant change.
And it might be killing them.
Dr. Susan Lewis, professor of biology and marine biology and one of the faculty who has led much of the research at the ecological field station over the years, likens it to a junk food diet, an unhealthy and unnatural change that could have ripple effects quite a way up the food chain.
Past research at the field station has measured the change in tree populations by way of census counts. More recently, research has begun to explore the ramifications of that changing population, and that leads us to the changing diet of amphipods and to the presence of Nicholas Gibson and Haley Groelle at Prairie Springs this past summer, after the two had already graduated.
The two had become involved in the ongoing research at Prairie Springs in the fall of 2016, as students in Lewis’ ecology class, BIO333. Each then signed up for an independent research class in the spring semester, so they could delve more deeply into the diet and health of the amphipods.
And then, after they graduated and tossed aside their robes and mortar boards, they came back to Prairie Springs, and to the amphipods.
What’s remarkable about this is that neither one of them is pursuing a career in environmental science. Gibson is hoping to attend medical school, Groelle dental school. Chances are really good that the digestive health of these diminutive shrimp will never factor into their future education—or careers.
But science is research and research is learning, so the two grads who are still learners are back to finish—or at least advance—the work they began. “Once they started this research, they wanted to finish it well,” said Lewis. “They didn’t get a conclusive end point during the school year. And they also have aspirations to get something published.”
Buckthorn leaves contain a chemical compound called emodin. In birds, emodin acts as a sort of laxative, helping ensure that birds which eat buckthorn seeds pass those seeds, helping the trees spread. Amphipods seem to prefer buckthorn leaves over the ash, but past research showed a lower survival rate for amphipods munching on buckthorn versus ones fed ash. In the labs at the Paul Fleckenstein Research Laboratory, Carroll researchers were able to determine that higher concentrations of emodin in the water negatively impacted amphipod survival rates. But just how much is too much, and do emodin concentrations get that high in natural settings? Without those answers, the earlier research isn’t of much practical real-world use.
This summer, Gibson and Groelle collected more amphipods from the stream at Greene Field Station, to see how they fare. They also gathered water samples from various sections of the stream, to determine if different parts of the stream contain different concentrations of emodin.
According to Gibson, he is driven now by curiosity. “Research wasn’t always at the forefront of my thinking,” he said. “But after starting this research, I really enjoy it. It’s a mental challenge—trying to figure out why things are the way they are. And, you know, medical schools think highly of research experiences.”
Having research papers published or presenting work at major conferences is the norm for graduate students, but less common for undergraduates—unless you attend Carroll. It’s true that this kind of research experience at the undergraduate level is a great competitive advantage for students hoping to attend graduate school or a professional school, according to Lewis, but the benefits go beyond the obvious résumé builder.
“Research work of any kind demonstrates and builds really important and very transferable skills,” said Lewis. “When they undertake research, students learn to work independently, collect precise data and develop problem-solving and critical thinking skills. What school or employer doesn’t value those?”
As for what they may uncover at Prairie Springs, well, amphipods everywhere are waiting to hear.