July 25, 2024
Many are known as phytoplankton, photosynthetic organisms that produce their own food using sunlight, carbon dioxide and other nutrients, much like plants do on land. But for the past decade, scientists have been shedding light on mixoplankton, which straddle the line between the plant and animal kingdoms by both photosynthesizing and preying on other organisms.
It was mixoplankton that ecology major Michael Rose ’25, of Far Hills, New Jersey, was on the hunt for this summer through a research collaboration between the labs of Sophie Charvet, assistant professor of biology, and Jack Holt, professor of biology. The professors combined their expertise in lake ecology and algal culturing to identify and isolate key mixoplankton from local freshwater ecosystems — including Walker and Faylor lakes in Snyder County and a small pond on Susquehanna’s campus — with the goal of obtaining a single organism that could be grown in the lab to run experiments quickly and efficiently.
“Picture a pond and within this pond, there are millions of photosynthetic organisms. It would be extremely difficult to study mixoplankton in this setting,” Rose said. “Now imagine plucking a single organism and attempting to grow it in a lab setting. That is what I did this summer.”
It took several weeks, but after much perseverance, Rose was able to isolate a single, unicellular organism that will be maintained in Charvet’s lab where it should reproduce indefinitely. Holt believes the organism they isolated is a chrysophyte called Ochrostylon, a taxon that can swim around or attach to surfaces and send out extensions, possibly to grab on to bacteria. Moving forward, Charvet will study the organism to better understand how different environmental conditions impact the balance of photosynthesis and predation in this mixoplankton.
“Our capacity to isolate individual mixoplankton cells from environmental samples, and thus obtain novel pure lab-grown cultures, will allow us to develop experiments on their specific feeding dynamics in both the lab and in the field,” Charvet said.
Rose’s work was exacting. Because he was working with such small samples, he first needed a very narrow pipette to extract samples. Rose heated the tip of a pipette over a flame until the glass softened. He then used tweezers to gently stretch the tip of the pipette, which elongated and narrowed it until it was small enough to suit his needs.
When conducting research in the lab, Rose said he found it “thrilling.”
“Having this culture on campus will grant us the ability to test a large range of hypotheses, allowing us to open doors to better understand mixoplankton ecology as a plant-animal hybrid,” Rose explained, “and turn our understanding of aquatic ecology upside down.”
After graduating from Susquehanna in December, Rose plans to attend graduate school and is considering environmental consulting before earning his doctorate to enter academia.