New study tracks microplastics in watershed

January 5, 2022

Scientists at the University of Maryland Center for Environmental Science are embarking on a research project that will lay the foundation for plastic research in the Chesapeake Bay. The two-year NOAA Marine Debris Program funded project begins in January and will track how microplastics move through the Choptank River watershed on the Eastern Shore of Maryland. The project studies the fate and transport of microplastics, providing a baseline of understanding of what kind of plastics exist in the waterway and how they move through coastal systems, particularly how marsh wetlands and underwater grasses impact their flow and where they end up during different seasons throughout the year.

Studies have estimated that up to 95% of the waste that accumulates on shorelines, the sea surface, and the seafloor is plastic. This study will work to understand what kind of plastics exist in the waterway and how they move through coastal systems.

“A lot of attention is paid to the giant garbage patch in the Pacific Ocean, but those plastics came from somewhere.  We have to understand where they are coming from and what happens to them before they get to the ocean,” said Associate Professor Jamie Pierson. “How microplastics transit through a system like the Choptank and its features—marshes, SAV beds, wetlands—might affect transport from source to open water.”

Studies have estimated that up to 95% of the waste that accumulates on shorelines, the sea surface, and the seafloor is plastic. To date, most published studies on plastic debris have focused on marine ecosystems and not estuaries, rivers, or freshwater systems.  Even fewer studies have focused on the interaction of coastal wetlands, such as underwater grasses or marshlands, and the accumulation of microplastics.  

Plastic debris occurs in different sizes and washes up on beaches, floats on the water surface, and sinks to the water's floor. Large pieces of debris are most obvious, but increasing attention has been paid to microplastics, which are less than 5 millimeters in size, or smaller than a pencil eraser. These smaller particles have specific and important human and ecological health implications because they can easily degrade and enter the food chain where they are ingested by the creatures at the base of the food chain.  

The project will develop and model scenarios to determine which factors and mitigation strategies could have the greatest impact on reducing marine debris in riverine environments. All of the data gathered will be made available to stakeholders and policymakers from agencies such as NOAA and the Maryland Department of Natural Resources, as well as local agencies and NGOs to be applied to coastal wetland systems, locally and globally.

Jamie Pierson
William Nardin

“The goal is to develop a budget that illustrates plastic debris input and retention in marsh and open water habitats of the Choptank river system,” said Assistant Professor William Nardin. “Ultimately, this information will allow stakeholders to examine how plastic debris deposition differs across habitats, different flow regimes, and different plastic loads, and to assess potential management strategies to mitigate plastic pollution.”

Plastic samples of all sizes, from plastic bags to microplastics barely invisible to the naked eye, will be collected and examined. Experiments will look at six different types of plastic, which degrade differently and have different densities, and how they may be trapped or move differently in different places in the river at different times of year.

A special microscope that uses short-wave infrared radiation camera will identify the different types of plastics, which emit different wavelengths and patterns of light. A drone outfitted with a special camera will also be used to scope out larger plastic debris in the watershed from above. It can identify different types of plastics, from plastic bag from beach ball to water bottle.

“Potentially, we’ll be able to make the connection between bigger pieces of plastic in a marsh that break down, and the pieces feeding into river system leading to microplastics in the water. We’re hoping to figure out if different types of debris get moved in different ways,” said Pierson.

The project will also create a group made up of experts and stakeholders that will advise the research in specific ways to ensure that the outcomes of the project are relevant to policy makers and directly inform management actions regarding plastic marine debris.