Undergraduate DMV Microplastics Study

By: Ben Rhoades

I can see plastic everywhere now– and not just the water bottles on the side of the trail or the plastic bags in branches, but the tab you pull off of a disposable squirt bottle and the tiny corner torn off of a granola bar. The most visually impactful part of this summer has been picking through fully processed microplastic samples as we work to quantify just how much plastic pollution is present in the Potomac River and the streams that feed into it.

Microplastics are pieces of plastic, either fragmented or intentionally produced, that are between 5mm and 0.3mm in diameter and are the center of increased media and academic attention. My lab partner and I have spent this summer studying these small bits of plastic in local waterways hoping to build off of the work of Mason PhD student Doreen Peters and the published work of Yonkos et al. (2015) who reported on microplastic in the Chesapeake Bay. Despite the work of both scientists, no data has been published on the presence, abundance, or concentration of microplastics in the Potomac River. This is where Han and I enter the scene.

Most microplastics research focuses on those plastics found floating at the surface of aquatic environments using a buoyant net named after its look-alike a Manta Ray. Using one of these Manta nets housed at the Potomac Science center, we’ve sampled Hunting Creek in Alexandria, VA; Gunston Cove in Woodbridge, VA; and the Anacostia River in Washington, DC. However, we also have used a novel stream sampling approach that uses a round-mouthed net anchored to either side of a stream and left for an hour to passively collect microplastics. Our lab’s principle investigator, Dr. Foster, and I sampled Accotink Creek, Cameron Run, and the Northeast Branch of the Anacostia River using our self-engineered technique. Finally, in an attempt to see if there is movement of microplastics into the food web, we extracted and analyzed the digestive tracts of four catfish.

Manta net collecting plastic near National Harbor, DC

Through this project, I hope to have some idea of an ideal sampling method that is representative of the who ecosystem a researcher is investigating, whether it is surface water sampling, sediment sampling, or fish-gut analysis. Also, am testing whether these sites differ in each of those sampling methods, and if so, what contributes to those differences. We have just finished our sample processing, which involved hours of drying samples, chemical digestion, picking at and counting plastics under a microscope, and finally I will have a chance to crunch our numbers and test these hypotheses.

Looking back, I thought I would know what to expect with this summer: sampling, processing, analysis, etc, however, I’ve learned that each research experience is unique and rewarding in its own way. First of all, becoming familiar a with a completely new and ever-growing field of literature has been an exciting challenge. Also, working with old and new faces in the lab and in the field, I have learned that all PIs and lab partners are different and that relationships and expectations are always… plastic.