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December 7, 2023

Plastics are found everywhere, making their way into our waterways and oceans as litter or improper waste disposal. Microplastics-tiny plastics not easily seen by the naked eye-are suspected of posing a risk to aquatic food webs and have the potential for human ingestion. 

Scientist using a fluorescing stereoscope for counting microplastics
WFRC scientist Lisa Wetzel uses a fluorescing stereoscope to look for microplastics in samples of Smallmouth Bass tissue provided by the Nez Perce Tribe, Idaho.

Plastics are found in waters throughout the world. As they break down into microplastics (plastics smaller than 5 mm in size), they proliferate and are detected in the water column and sediments, then ingested by invertebrates, fish, birds, and mammals. From physical damage to toxic contamination, microplastics are suspected of posing a risk to aquatic food webs. But where, what type, and to what extent are they affecting our fish?

Our ecology team was recently contacted by the Nez Perce Tribe Water Resource Division to collaborate on a pilot study to determine the presence/absence of microplastics in gut contents of Smallmouth Bass from the Clearwater River, ID. The Nez Perce Tribe have an ongoing water quality monitoring program that includes monitoring certain fish populations. The tribe is interested in establishing baseline levels of microplastic pollution now, then track pollution levels to document any changes that may occur over time. As our society has increasingly relied on plastic products and as those products age and break down, an increase in the amount and distribution of microplastics is expected.

This study and the resulting data build on a publication by USGS scientists that evaluated microplastic ingestion in Chinook Salmon. Through this current collaborative effort, scientists are developing new protocol based on existing publications, including one paper that uses Nile Red fluorescent tagging in a rapid-screening approach to detect and quantify microplastics. Nile Red is a dye which adheres to many plastics and fluoresces, aiding in the visual identification of individual microplastics.

Any plastics identified within the bass gut samples will be categorized by color, shape, and size. Image analysis software will be used to measure the microplastics and to visually document the findings. Applying and adjusting the techniques to fisheries questions will help in guiding future work in monitoring and evaluating for microplastics and their impact on fisheries resources.

WFRC will continue to work with our tribal partners and other collaborators to better identify the extent of microplastics and their effects on aquatic species and their environments.


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