Biofilms, Plastics & Water Quality Along the Mill River

Niveen Ismail loves zooplankton. An associate professor of engineering at Smith and the inaugural recipient of the Ellen Braestrup Strickler ’57 endowed faculty research fellowship in the Center for the Environment, Ecological Design and Sustainability (CEEDS), Ismail has spent the past ten years studying these microscopic organisms, which she calls “small but mighty.” Zooplankton might not be visible to the eye, but they are a crucial part of the water system. Ismail is particularly interested in their relationship with contaminants, both their ability to remove contaminants from water and the impact of contaminants on them.

It was not inevitable that Ismail would end up devoting her research career to aquatic microorganisms. A chemical engineering major as an undergraduate, she worked for five years at Exxon Mobile after graduation. Through volunteering at the Philadelphia Zoo, though, she developed an interest in wetlands, which led to a masters in biology. Missing engineering, she decided to combine her interests and become an environmental engineer, specializing in water quality and “impacts of living organisms in the aquatic environment.” Her Stanford Ph.D. dissertation focused on using bivalves to improve water quality. She came to Smith in 2015, and her research on zooplankton began.

Ismail’s Strickler fellowship project is a sampling study focusing on plastic contamination in the Mill River watershed. Through the study, Ismail hopes to understand whether plastic type affects the kind of bacteria (biofilm) that grows on it, and whether the biofilm that grows on plastics is different from that which grows on a natural substrate—in this case, wood. A key benefit of this project for her is that it has gotten her out of the lab. “It’s fun to do fieldwork where I can’t control factors,” Ismail says. “Rather than doing it in my lab and trying to manipulate [things], we’re just seeing what happens when nature runs its course.” Her CEEDS fellowship has also given her the opportunity to base a project in the Mill River. “There are many things that drew me to Smith,” she says, “but I was excited about having the Mill River as my backyard.”

Ismail also appreciates the collaboration the project has required. Her students worked closely with Smith’s Center for Design and Fabrication to design the mechanism by which they could collect the samples. The students cut different types of plastic sheets into small pieces, which were then enclosed within stainless steel tea strainers attached to a larger metal cage. This system has allowed the cages to stay in place while the plastic samples in the tea strainers can be brought back to the lab for analysis. In May 2025, the cages were placed at six sites along the Mill River, from Goshen in the north, through Williamsburg and then on to Paradise Pond. Ismail’s team sampled weekly for the first month and then monthly through November. The samples will remain in the six locations through May 2026.

Ismail and her students have been assessing the samples by location—are there differences, for example, between samples from the more rural Goshen and the more developed Paradise Pond? They are also looking for differences in the samples between the moving water in the Mill River versus the more stagnant water in the pond as well as the differences in samples taken across the seasons. One of Ismail’s collaborators on the project is Professor of Geology Amy Rhodes, who, with her students, is exploring the differences in water and sediment chemistry of the site locations. And thanks to a suggestion from Professor Emeritus of Geology Bob Newton, Ismail made sure that one layer of the strainers was in contact with the sediment. “People have done this type of work before looking at biofilm formation on plastic types,” Ismail says, “But ... one of the knowledge gaps we identified is that people haven’t looked at multiple locations within a watershed. And people haven't looked at the differences between what would grow if you have it in the water column versus ... ending up in sediment. So, seeing that difference, I think, is going to be really interesting for us.”

Karina Padilla ’26, who has been working in Ismail’s lab since their first year at Smith, is writing an honors thesis based on the sampling study and will be sequencing the data gathered to determine the types of bacteria growing on the plastics. “I think what Karina will be able to tell for their thesis is what types of organisms are growing and [whether] there is a difference between what we see based on plastic type and location,” Ismail says. “Further student work would be looking at how the water chemistry comes into play, how the sediment characteristics come into play. Can we start looking at land use patterns? [We’d be] looking ... more holistically at the entire system.”

Eventually, Ismail hopes to connect this project back with the zooplankton she so loves. “When I approach an environmental problem,” she says, “The first step for me is understanding more about contaminants. So, the study really is providing a baseline of what is happening with plastics in the environment.” Ismail anticipates eventually adding in the element of water-borne viruses and “seeing how these plastics with biofilm then interact with viruses.” Then zooplankton could be introduced as well. Some types of zooplankton inactivate viruses while other types harbor them. Could “viruses ... potentially be sorbed onto a piece of plastic, which then the zooplankton eat? That’s ... the longer-term vision of ... why this could be important.” She hopes that the project will lay the foundation for potential solutions for contaminants in water further down the line. “We need to understand how these plastics behave in the environment to even think about treatment. So, this is the very first step of understanding [that].”

Ismail is reconciled to the long-term nature of her work, given the ten years she’s spent studying two or three types of zooplankton. In her Smith job talk, she mentioned specifically wanting to work with zooplankton and plastics, but this project is, in fact, her first time working with plastics. “It took me ten years ... to feel at a point that I could introduce plastics into my research,” she says. “I tell my students when they come to work in my lab that you could work on something for three years. And hopefully maybe in another five years, I'll reach out to you and ... [tell you] the results.”