A big problem? Assessing microplastic abundance in a fish species from small freshwater streams

Background/Question/Methods

Plastic pollution is an increasingly important environmental concern, especially in aquatic ecosystems. A recent focus has been on microplastics, which are fragments of any type of plastic less than five millimeters in length. However, our understanding of microplastics has been centered much more on marine systems than freshwater systems, leading to an incomplete understanding of the potential prevalence and scope of this environmental concern. The goal of this research was to help make strides towards a greater understanding of microplastics in freshwater ecosystems. This research focused on small, headwater streams in northcentral Massachusetts (USA) and a small freshwater fish species that inhabits many streams throughout much of the eastern United States, the Blacknose dace (Rhinichthys atratulus). Microplastic abundance was assessed and quantified in water samples from 14 streams and about 20 fish from each of five streams.

Results/Conclusions

Microplastics were found in all 14 streams sampled. There was considerable variation in the number of microplastics in each sample. Most of the streams contained less than 100 pieces of microplastics, but one stream had over 400 pieces. Microplastics were discovered in fish samples from all five streams. There was variation in the amount of microplastics in the fish, although less than in the water samples, with a range of about 30-60 pieces. The number of microplastics was not related to the length of the fish or the amount of microplastics in the water, perhaps suggesting that microplastic ingestion by Blacknose dace may be a passive process. Together, these results also illustrate that microplastics in freshwater ecosystems should be considered when trying to understand the full impact that this source of pollution may have on ecosystems.