Scientists will study the movement of plastic pollution in the Choptank River

February 24, 2022

Plastics swirling in ocean gyres have recently attracted media and research attention. But what happens to parts that cross rivers closer to home – or get trapped in swamps and washed up on shores along the way?

Scientists at the University of Maryland’s Environmental Science Center aim to answer that question through a two-year research project that kicks off this year. The National Oceanic and Atmospheric Administration’s Marine Debris Program selected the project as one of five to receive funding from a national pool of 72 applicants.

The effort will focus on the Choptank River, the largest waterway on the Delmarva Peninsula, which runs through a relatively rural and agricultural region. With the university’s Horn Point Laboratory located on its shores near Cambridge on Maryland’s east coast, the Choptank has been studied extensively, making it an ideal test case for understanding how microplastics move through river systems.

Another microplastics project based in the Chesapeake Bay area also recently received a federal grant. Last year, the National Science Foundation’s Historically Black Colleges and Universities Science and Engineering Research Infrastructure Program awarded Morgan State University $1 million to study the impact of microplastics on marine life. . The work is based out of the university’s estuarine lab in Calvert County, MD, with a focus on training students to research microplastics.

Microplastics have been found everywhere scientists have looked for them, including in the air above the Pyrenees mountains. This is also true in the Chesapeake region, where the US Geological Survey has detected the small plastic particles at sampling stations in the bay and its tributaries.

Next, Cambridge researchers want to know where they end up and what happens along the way.

“We’re looking at how microplastics move through the system and how they’re affected by the system,” said James Pierson, biological oceanographer and associate professor at Horn Point. “As the river flows, what happens when [microplastics] pass these marshes? How is that different from what happens in the middle of the canal?”

Other research in the region suggests that the seagrass beds in the bay could serve as catchment areas for microplastics. One study found the particles at significantly higher concentrations in seagrass beds than in an adjacent water column of the Potomac River. The beds are also a hotbed of ecological activity where species such as blue crabs could mistake the tiny pieces of plastic for food.

Working with fellow Associate Professor William Nardin, who specializes in hydrodynamic modeling at Horn Point, the Choptank researchers plan to use old and new tools to answer their questions. The federal grant of $167,155 will support research that could apply to other rivers in the bay’s watershed and beyond.

In addition to collecting microplastics with a net behind a boat, Nardin will use a drone with a special camera to locate larger plastic debris over a wide area. The work will analyze plastic samples of all sizes, from intact bottles and bags to pieces no bigger than a pencil eraser.

Scientists will also use more widely available microscope and camera technology — rather than that available only in high-tech labs — to identify different types of microplastics extracted from water. This could help set the stage for school groups or citizen scientists to participate in microplastics research if they can use the equipment they have to identify types of plastic.

Experiments will examine how half a dozen types of plastic polymers degrade and move downstream. Are plastics more likely to be trapped in the marsh in summer, when the seagrass beds are thicker, and then reach the stream bed in winter? Are denser plastics likely to sink into bottom sediments while lighter pieces sink farther from shore?

“This will help us estimate how the morphology of the river affects the flow of plastic through it,” Pierson said.

All the data will feed into a hydrodynamic computer model to explain and predict how plastics move through the river and what factors determine where they land. The hope is to make this information applicable to a wide range of water bodies, informing policy decisions to reduce plastic pollution.

Matt Robinson, environmental protection specialist with the District of Columbia’s Department of Energy and Environment, said the work will help guide the bay program’s plastic pollution action team. of Chesapeake, which he chairs.

“Research like this is critical to understanding the impacts of plastic pollution on the Chesapeake Bay and its watershed,” Robinson said. His team stressed the need for this type of research in the bay’s waters “to understand the ecological risk of plastic pollution and how these pollutants might impact restoration success.”

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Bryce K. Locke