Date of Award

Spring 4-28-2020

Document Type

Honors Project

Degree Name

Bachelor of Science


Earth and Environmental Sciences

Department Chair or Program Director

Hayob, Jodie

First Advisor

Frankel, Tyler

Second Advisor

Kisila, Ben

Third Advisor

Oldham, Davis

Major or Concentration

Environmental Science (Natural Science Concentration)


Microplastics have become an emerging contaminant of concern in freshwater systems as a component of wastewater treatment plant (WWTP) effluent, household discharge, and industrial outflows. While microplastics have been detected in aquatic environments throughout the world, our knowledge regarding microplastics in the Chesapeake Bay Basin and their impacts on aquatic invertebrates combined with chemical pollutants is limited. This study consisted of two parts: a field-based assessment examining the spatial distribution of microplastics in the Rappahannock River, VA; and a lab-based analysis examining the effects of polyethylene microplastics and the pesticide methoxychlor on the viability and mobility of Daphnia magna. Microplastics were more abundant in sediment downstream of a major WWTP outfall site and equally abundant in surface waters at both sites. We suggest that residence time plays a major role in microplastic deposition and that downstream zones are at increased risk. Methoxychlor was found to decrease mobility after 48 hours, whereas microspheres alone caused no significant debilitation. Combinations of the two toxicants resulted in increased mortality rates at moderate mixture treatments and decreased mortality at the highest mixture treatment. Thus, our results suggest that level of microplastic contamination influences the degree of contact organic pollutants may have on vulnerable species.