The shape of microplastics can influence how deadly a viral infection can be for fish, according to new research from William & Mary's Virginia Institute of Marine Science (VIMS). The findings suggest that some forms of plastic pollution pose greater biological risks than others, offering scientists a potential path toward reducing the environmental impacts of microplastics.
Recently published in Environmental Toxicology and Chemistry , the experimental study found that rainbow trout exposed continuously to nylon microfibers were twice as likely to die from a viral infection compared with fish exposed to the virus alone.
The results demonstrate that, even if such particles on their own may not be fatal, "microplastics have really significant impacts," explained lead author and VIMS & Batten School of Coastal & Marine Sciences Professor Meredith Evans Seeley.
Over eight weeks, the researchers monitored 800 juvenile rainbow trout housed in 40 laboratory tanks at VIMS. Different groups of fish were exposed to either long, thin nylon microfibers or small, rounded nylon particles. Then, designated groups were exposed to infectious hematopoietic necrosis virus (IHNV), a major pathogen affecting trout.
Fibrous microplastics were far more impactful than sphere-shaped microplastics, which did not significantly increase virus-related mortality. The results indicate that the shape of pollution particles can matter a great deal for fish health, a major finding around the rapidly emerging environmental issue of microplastics.
"[The finding] creates an opportunity to identify the worst forms of pollution and come up with solutions," said co-author and VIMS & Batten School Professor Andrew Wargo.
The researchers suspect that the physical properties of fibers, particularly their elongated shape and rigidity, may damage protective tissues such as the gills, potentially allowing viruses to enter the body more easily.
"It's likely creating an easier path for that virus to infect that host," Seeley hypothesized.
Identifying traits that make certain plastics particularly harmful may inform environmental monitoring, pollution-reduction strategies and the development of safer materials.
Although the study demonstrates that nylon microfibers can exacerbate viral disease under controlled laboratory conditions, the researchers caution that more work is needed to determine how those findings translate to other environments. Future studies may examine different concentrations, particle sizes and exposure durations to better understand real-world risks.
