Characterizing and enumerating microplastics (MPs) have received considerable attention in recent years. Most attention has focused on major waterways and especially in the water column. However, less is known about MPs in smaller lakes and tributaries, as well as in sediments, under both base flow and storm flow conditions. This study examines the role of an unnamed tributary in transporting microplastics and 6PPD-quinone from a major state highway into a small, salt-impacted, lake in Grand Rapids, Michigan. Water and sediment samples were collected over a one-year period to characterize microplastic types, abundances, and seasonal variability, while environmental conditions were monitored to assess storm event impacts. Results confirmed widespread microplastic presence in both habitats, with abundances ranging from 61–16,390 MPs/L. Many microplastics were black fragments, often unidentifiable but suspected to be rubber-derived. Storm events significantly increased microplastic transport, particularly in the tributary, where concentrations peaked at 16,390 /L during fall stormflow. 6-PPD-quinone concentrations were very low overall (<1 ng/L) with spikes during storm events in the tributary (up to 201 ng/L). Sediment analysis revealed higher microplastic abundances in the tributary compared to the lake, with black fragments dominating in both habitats. These findings underscore the critical role of storm-driven runoff in microplastic and chemical transport, highlighting the need for improved road infrastructure design to mitigate environmental impacts on downstream water bodies.

Characterizing and enumerating microplastics (MPs) have received considerable attention in recent years. Most attention has focused on major waterways and especially in the water column. However, less is known about MPs in smaller lakes and tributaries, as well as in sediments, under both baseflow and storm flow conditions. This study examines the role of an unnamed tributary in transporting microplastics and 6PPD-quinone from a major state highway into a small, salt-impacted lake in Grand Rapids, Michigan. Water and sediment samples were collected over a one-year period to characterize microplastic types, abundances, and seasonal variability, while environmental conditions were monitored to assess storm event impacts. Results confirmed widespread microplastic presence in both habitats, with abundances ranging from 61 to 16,390 MPs/L. Many microplastics were black fragments, often unidentifiable but suspected to be rubber-derived. Storm events significantly increased microplastic transport, particularly in the tributary, where concentrations peaked at 16,390/L during fall stormflow. Concentrations of 6-PPD-quinone were very low overall (<1 ng/L), with spikes during storm events in the tributary (up to 201 ng/L). Sediment analysis revealed higher microplastic abundances in the tributary compared to the lake, with black fragments dominating in both habitats. These findings underscore the critical role of storm-driven runoff in microplastic and chemical transport, highlighting the need for improved road infrastructure design to mitigate environmental impacts on downstream water bodies.

The plastisphere can have a significant impact on the buoyancy, toxicity, and functionality of microplastics (MPs). Little is known about plastisphere structure, especially in salt-impacted lakes, despite the growing focus on the salinization of lakes. Virgin polypropylene and polyethylene terephthalate MPs were incubated for two weeks in flow-through containers in the epilimnion (low phosphorus, low salinity, high light) or hypolimnion (high P, high salinity, and low light) of a salt-impacted lake and then incubated in the lab in either their original water or water from the alternate depth to determine plastisphere response should the lake fully turn over. Environmental factors, including phosphorus concentration, light level, salinity level, and temperature, rather than polymer type, influenced community composition. Bacterial communities on MPs in the epilimnion exhibited higher diversity compared to those in the hypolimnion. Algal communities on MPs showed a similar trend, with greater diversity in the epilimnion. Overall, initial community composition had a stronger influence on community structure (priority effect) than the environment in which the plastisphere was grown. For those plastisphere communities capable of responding to species-specific desirable environmental conditions, lake mixing that results in increases in phosphorus and salinity from the hypolimnion to the epilimnion will increase the abundance of algae on MPs in the photic zone.