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Study: Microplastics Infiltrate Region's Salt Marshes

A salt marsh on Plum Island, Mass.
S. Bond

Woods Hole scientists are finding microplastics trapped in salt marsh ecosystems across the region.

A team from the Marine Biological Laboratory took water samples at six different estuaries in the Waquoit Bay system on Cape Cod and in New Bedford Harbor, and found microplastics in all of them.

“These are very important ecosystems. And the fact that we knew very little about microplastic contamination captured my imagination and made me pursue this project,” said lead scientist Javier Lloret.

About 8 million tons of plastic enter the ocean each year, but until this study, no one had analyzed the marsh sediments on Cape Cod for microplastics before, he said.

Ultimately, the team found a clear relationship between urbanization of the land and the amount of microplastics that were found in salt marshes.

“When 50 percent of the land is occupied by humans and humans have houses, parking lots and commercial areas, roads and all those uses … the number of microplastics in salt marshes grows exponentially,” Lloret said.

Salt marsh ecosystems filter nutrients, sequester carbon, promote biodiversity, and protect against erosion. Microplastics could create be serious implications for the entire food web, starting with oysters, scallops, and other filter-feeders.

“As these animals are feeding or are being fed by other animals they might also be transferring the microplastics,” Lloret said. “And that can potentially mean that we are also consuming those microplastics when we consume fish or shellfish with potential effects to human health.”

The researchers’ study, published in Environmental Advances, focused on two types of microplastic pollution: fragments (from the breakdown of larger plastic pieces) and fibers (thread-like plastics which tend to shed from clothing and fishing gear), but were surprised to find that microplastic fibers didn’t have the same relationship with urbanization.

“With the fragments, we found that they are directly related to the level of population that you have in the surrounding area,” he said. “But … the fibers showed no relationship with the amount of people whatsoever. So what that's telling us is that the fibers do not depend on the people that are living in the surrounding area, but depends on the people that live in the region as a whole.”

Overall, Lloret said, as population density and plastic use has increased in the last 25 years, the concentration of microplastics has at least doubled.

Future research, Lloret said, seeks to understand how plastic particles are arriving in the ecosystem, what the main sources are, and how they’re impacting the food web of the organisms that live there. Meanwhile, scientists are urging national and local action to reduce single-use plastic products.