Study shows microplastic increase in river’s bass

Tiny plastic particles, also called microplastics, were found in 100% of smallmouth bass digestive systems studied in 2019 via the Susquehanna University’s Freshwater Institute — capping an annual increase in the three-year study.

A total of 206 smallmouth bass were collected from 2017-19 from two different sites on the Susquehanna River and in Pine Creek. Samples were collected by the Department of Environmental Protection and the Pennsylvania Fish and Boat Commission, with Susquehanna University students studying each stomach for dietary contents and microplastic analysis.

“The diet analysis of smallmouth bass shows a large variety of prey items from several trophic levels suggesting that there are many pathways for the accumulation of microplastics,” said Dr. Jonathan Niles, director of the Freshwater Research Institute. “Our study will help increase the knowledge of what smallmouth bass consume in their diet and the presence and concentration of microplastics in freshwater fish species found in the Susquehanna River.”

The primary diet item in 2017 and 2019 was crayfish (53.8% and 46%, respectively). In 2018, macroinvertebrates (39.5%) were the top food item discovered.

However, the percentage of fish with microplastic particles — and the number of microplastics per fish — drastically increased in specimens in each of the three years.

In 2017, 87.5% of the samples contained microplastics, with an average of 2.3 microplastics per fish. That number climbed to 95.5% in 2018 specimens (6.1 per fish) and 100% of those collected in 2019 (28.9 per fish).

“One possibility for the differing number of microplastics could be the flow rate of the Susquehanna River, allowing it to gather more plastic waste and break it down with a higher flow rate,” said Niles, adding that the average flow increased in each of the three testing years.

The results are under review by the Pennsylvania Fish and Boat Commission, according to spokesperson Mike Parker.

“We participated in the study and are certainly interested in the findings, although we haven’t fully reviewed those findings and how they’ll influence the next steps,” he said. “As an agency, we always want to be a part of the answer, not the problem.”

​​Representatives of the state’s Department of Environmental Protection have yet to see the study, according to spokesperson Megan Lehman, but is looking forward to reviewing it.

“The DEP works closely with the PA Fish and Boat Commission, university research centers including Susquehanna University, and other stakeholders to better understand and advance science-based solutions to water quality issues affecting fish populations and aquatic health in the Susquehanna River and waterways across the Commonwealth, in keeping with our mission,” she said, adding that the DEP offers background information on public health and fish consumption on their website by clicking here.

Results of Susquehanna University’s smallmouth study were presented at 14th Annual Susquehanna River Symposium and the 2020 technical meeting of the Pennsylvania Chapter of the American Fisheries Society by Timothy Parks (class of 2020) and Niles. Parks’ senior thesis was also cited by a Scientific and Technical Advisory Committee report to the Chesapeake Bay Program.

“In our efforts to engage and educate the public about potential threats to our river-based resources, this study is pretty significant because it provides definite, measurable evidence of plastic-based pollution within our greater watershed,” said Middle Susquehanna Riverkeeper John Zaktansky. “Our association is committed to helping determine the source of these microplastics and how we can best respond to the threat. This is an important reminder that each of us need to do our part to reduce waterway littering issues and raise awareness about the impact we have on our natural resources.”

Lehman added that there are many ways each person can help cut back on the plastic-based issues within the greater watershed.

“The DEP strongly encourages the public to help reduce plastic pollution in the environment by reducing the use of single-use plastics, purchasing products made with recycled materials when possible, recycling plastics where recycling is locally available and properly disposing of plastics that cannot be recycled,” she said.


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