EMU students study invasive freshwater jellyfish in Dexter Township through new course

EMU Professor of Biology Cara Shillington says she was surprised that there wasn't much research published on the topic of the tiny freshwater jellyfish that her students examined in Pickerel Lake.
Students taking a new biology course at Ypsilanti's Eastern Michigan University (EMU) are getting hands-on experience that could break new ground in research on invasive, freshwater jellyfish.

EMU Professor of Biology Cara Shillington says she was surprised that there wasn't much research published on the topic of the tiny freshwater jellyfish – c​​raspedacusta sowerbii, also known as peach blossom jellyfish – that her students examined in Pickerel Lake in Dexter Township.
EMU Professor of Biology Cara Shillington.
Before launching the Jellyfish Research course in autumn of 2022, she contacted several organizations, including Michigan's Department of Natural Resources and the Great Lakes Environmental Research Laboratory, to see what they knew about this non-native species.

"Nobody was tracking any of this," Shillington says. "I like doing surveys and looking at changes over time, so we'll have a class every fall semester, go out and do some sampling, [and] see what things are changing and what's staying the same."

"Everybody should be taking an invertebrates class"

Shillington teaches biology students about invertebrates of all kinds. She started out specializing in tarantulas.

"Everybody should be taking an invertebrates class. They are 96% of the animal species on earth," Shillington says. "The range of what they look like, the way they live, [and] the diversity is incredible."

The jellyfish course allowed Shillington to take students beyond the classroom to view the jellyfish up close with hands-on fieldwork. Unlike the larger jellyfish people might have encountered in the ocean, these freshwater jellyfish are about the size of an adult human's fingernail. While all jellyfish sting their prey, the freshwater jellyfish are too small and weak to penetrate human skin, so they pose no risk to swimmers.

Shillington says there are two phases to all jellyfish's life cycle. The first is a sedentary polyp stage, when they settle down and attach to vegetation or the floor of a body of water. The second, or medusa, phase is the adult stage most people picture when they think of jellyfish. When many adult jellyfish appear in a body of water at once, this is called a "bloom."
Peach blossom jellyfish in the Eastern Michigan Biology Lab.
Because the survey work is so new, Shillington says she and her students aren't entirely sure of what a normal season of jellyfish "bloom" looks like at Pickerel Lake. Studying them year-to-year will help establish patterns. So far, it seems blooms are heaviest in August and September, so students had about a month of fieldwork at the beginning of the semester to collect samples to bring back to the lab on campus. Shillington says there may have been more jellyfish in the lake in 2021.

"We talked to people who live on the lake or who swim there, and they say we missed the real bloom," she says.

Lance McCarty, an EMU senior majoring in environmental science, was part of the inaugural jellyfish course, and says it was "a great time." He says students would swim across the lake, carrying bags to capture jellyfish, while others would follow in a kayak to record water data including temperature, turbidity, and clearness.

"The jellies that we collected were taken back to EMU campus where we could make other observations about them like behavior, size, reaction to light, or feeding habits," McCarty says. "My favorite part of the class was being in the water and seeing the aquatic environment. It's an uncommon experience. It's so exciting to see the plant and fish variety, and it's so cool to see the jellies."

What's next for the jellyfish course?

Grad student Rachel Koski has been working on jellyfish as well, and plans to expand on the work already done for her master's thesis. This spring, she'll visit the lake to track the jellyfish earlier in the year so her class can get a better idea of how big a typical bloom is and when blooms are heaviest.

"Freshwater jellyfish have been seen in the Great Lakes. I grew up on Lake Huron, and I spent 22 years of my life without me realizing it," she says. "It was a really cool opportunity to get undergraduates and graduates into the field and into the water, which isn't common with classes here at EMU."

Shillington says that while the jellyfish are technically "invasive," nobody knows if they're harmful. One possible effect such a study might find is that native larval fish might suffer from competing with jellyfish for the same diet of small zooplankton, she says.

"As far as we know, they don't seem to have a major impact, but nobody has necessarily done that type of study," Shillington says. 

Koski says it's exciting to see so many "gaps in the jellyfish literature," because that means lots of fruitful avenues for study and submitting papers to journals. She's also thrilled that her interest in marine biology can be satisfied near home.
EMU grad student Rachel Koski.
"When I finished my bachelor's degree, I planned to do some kind of research in marine conservation if I could," she says. "Toward the end of my bachelor's [studies], I found corals and jellyfish really interesting, and just sort of stumbled into studying freshwater jellies. And I get to stay in Michigan, which I love."

Shillington says several people reached out to her after reading an EMU Today article about the course. One man had done some research on freshwater jellyfish in the '60s and told her about his experience. Another person who lives on a private lake invited Shillington's class to do fieldwork there in the future.

"It's so fun to hear from people that had some background and interest in this," Shillington says. 

Shillington says she hopes to incorporate some community outreach and education into the research project in the future as well, such as teaching visitors on-site at local lakes about the jellyfish or bringing samples into local schools. 

"This past fall was the first time teaching the class, so a lot of things are up in the air," Shillington says. "We don't know exactly what's going to happen with the jellies. We're going to get out into the field as much as we can next year, get a lot more organized, and then we'll know a little bit more."

Sarah Rigg is a freelance writer and editor in Ypsilanti Township and the project manager of On the Ground Ypsilanti. She joined Concentrate as a news writer in early 2017 and is an occasional contributor to other Issue Media Group publications. You may reach her at sarahrigg1@gmail.com.

All photos by Doug Coombe.
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