RESEARCH

This work aims to evaluate the impacts of glyphosate, a commonly applied herbicide ingredient, on periphyton dynamics in residential stormwater ponds within the Grand Strand. Ponds from low- and high-density residential developments were assessed in 2024 and  2025. The concentration of glyphosate and one of its degradation products, aminomethylphosphonic acid (AMPA), along with other water quality parameters, will be measured in each pond at the beginning of the study to determine baseline concentrations and overall pond health. A passive diffusion periphytometer, housing bottles containing a gradient of glyphosate concentrations, wias deployed in each pond to measure the periphyton community response through chlorophyll-a concentration. By assessing the impacts of this herbicide ingredient on periphyton dynamics, the study will evaluate water quality and pond functionality, which will inform future stormwater pond planning and management practices.

This work aims to evaluate the impacts of glyphosate, a commonly applied herbicide ingredient, on periphyton dynamics in residential stormwater ponds within the Grand Strand. Ponds from low- and high-density residential developments were assessed in 2024 and  2025. The concentration of glyphosate and one of its degradation products, aminomethylphosphonic acid (AMPA), along with other water quality parameters, will be measured in each pond at the beginning of the study to determine baseline concentrations and overall pond health. A passive diffusion periphytometer, housing bottles containing a gradient of glyphosate concentrations, wias deployed in each pond to measure the periphyton community response through chlorophyll-a concentration. By assessing the impacts of this herbicide ingredient on periphyton dynamics, the study will evaluate water quality and pond functionality, which will inform future stormwater pond planning and management practices.

This work was done by Alyssa Wentzel, a NOAA Hollings Scholar from the University of Delaware that I mentored during the summer of 2024.

Estuaries are the intersection of upland, rivers, and the sea that house a variety of unique habitats. With increasing coastal development, estuaries in the Grand Strand, South Carolina, are at risk for accumulating plastic debris, which can eventually break down into microplastics (<5mm). Murrells Inlet, SC, is characterized as an urbanized area with limited plastic policies, high rates of tourism, and high plastic consumption, making it susceptible to the influx of microplastics. In comparison, a nearby inlet, North Inlet, has little urbanization impact and limited access. We studied these two inlets to examine the impacts that urbanization has on microplastic distribution. We collected water samples at 5 different sites at each inlet (n=10) during an ebbing tide in June 2024 to analyze microplastic distributions, abundance, and composition to assess the fate and transport of microplastic pollution across these two inlets. Microplastics were analyzed and characterized on an Agilent LDIR 8700, which detected microplastics from 20-500 μm . The mean microplastics abundance across all locations in Murrells Inlet was 230.8 ± 64.77 MP/m3 while North Inlet average was 195± 78.21 MP/m3. We found that there was no statistical difference between the two inlets (p = 0.227), but patterns did emerge in distribution of abundance and particle composition across the estuaries. The most abundant particle composition was rubber, however, there was no statistical difference of rubber in these two inlets (p=0.079). Tire wear particles were most abundant in areas by boat ramps and were seen in smaller amounts in the other locations. Despite emerging similarities of microplastic abundance between these two inlets, Murrells Inlet experienced higher amounts of polytetrafluoroethylene (PTFE) (p=0.015) and polyethylene terephthalate (PET) (p= 0.054). Knowing there was limited differentiation between abundance of microplastics of pristine and urbanized inlets, these results point to a need for local mitigation and prevention efforts in order to reduce the load of microplastics into estuarine environments. 

Contaminants of emerging concern (CECs), like microplastics and pharmaceuticals, are a

growing threat to aquatic ecosystems across the globe. Microplastics can be transported into

waterways through a myriad of sources, including point sources such as wastewater treatment

plants (WWTPs) and nonpoint sources, such as runoff. The goal of this study was to evaluate the importance of non-point sources of microplastic pollution to the Huron River. To address this, I measured the microplastic load of the Huron River in Ypsilanti, MI, between September and November 2021 and May and August 2022 over a range of river discharge. There was a strong positive relationship between river discharge and microplastic load, suggesting that runoff is an important source of microplastic pollution to the river. To find out more information about this work, check out my  Master's thesis here!

Microplastics can act as vectors for other contaminants of emerging concern, such as pharmaceuticals, into biota. The goals of this study were to determine if aquatic filter feeders ingest microplastics, and how the interaction of microplastics and non-steroidal anti-inflammatory drugs (NSAIDs) affect filter feeders, using the invasive zebra mussel (Dreissena polymorpha) as a model organism. To these goals, I conducted manipulative experiments exposing zebra mussels in microcosms to microplastics and two types of NSAIDs (ibuprofen and diclofenac) in a factorial design. On average, mussels ingested 57.5 ± 35.2 MP/individual during the 24-day experiment. Results from this experiment indicate that exposure to microplastics, ibuprofen, and diclofenac for 24 days reduced mussel feeding rate in some treatments after 19-20 days but had no detectable effects on mussel growth and metabolism. To find out more information, check out my Master's thesis here!