Unfathomable amounts of plastic garbage have been created by humans, posing a hazard to ecosystems and even human health. The goal of recent research published in the journal Environmental Advances was to find out how microplastics accumulated in the salt marshes of southern New England, which are vegetation-filled wetlands that mark the land-sea transition.
“ Scientists all over the globe are discovering microplastics everywhere,” says Javier Lloret, a marine biologist at the Marine Biological Laboratory in Woods Hole, Massachusetts, “whether it’s at the bottom of the ocean or the top of the tallest mountains, or even in distant locations like the Antarctic.”
Despite their widespread use, scientists are only just beginning to understand the effects microplastics may have on our ecosystems, according to Lloret.
The researchers focused on the microplastics that collect in a salt marsh region in the current study, which was headed by Lloret and Rut Pedrosa-Pàmies, a marine biogeochemist at the Marine Biological Laboratory. Particles from the water and air tend to accumulate naturally in these environments, trapped by plants and leaves into thin layers of sediment that pile up over time, according to Lloret. “As a result, we believe that there will be a higher buildup of microplastics in this site than in other portions of the coast, such as an open shore.” Cores of sediment were taken from marshes in seven Massachusetts estuaries and analyzed, The researchers were able to compare places and look back in time, tracing the link between microplastic accumulation and the rate of adjacent urbanization, which they quantified using land occupancy data.
These cores were gathered from a variety of salt marshes, ranging from significantly human-impacted New Bedford port to “ almost pristine” salt marshes on Cape Cod, according to Pedrosa-Pàmies. The researchers broke up the sediment layers like cookie dough and dated them to around 1940, just as plastics began to make their way into everyday life. The microplastics were then removed from the sediments and quantified and categorized, distinguishing between microplastic fragments—which come from bigger plastic items—and microplastic fibers, which come from textiles or fishing gear. Because microplastics are so pervasive in our environment, including the atmosphere, the researchers say they took precautions to avoid contamination by wearing natural fiber clothes, inspecting microfiber filters for plastics in the lab, and utilizing plastic-free equipment.
The sediments in these ecosystems effectively trapped microplastics, which had been accumulating up in the area since the 1950s, as the researchers hypothesized. They also discovered that the more urbanized a region was, the higher the concentration of microplastics in the sediment. “However, it is not a particularly gradual, linear response,” Lloret explains. “At roughly a 50% level of development, there appears to be a threshold.” There won’t be a lot of microplastics until that threshold is reached, but after that, the authors discovered that the number of plastics rose rapidly.
“Another thing that was interesting was that we found a definite difference in the sorts of plastics,” Pedrosa-Pàmies adds, referring to fibers vs pieces. While microplastic pieces correlated with the extent of urbanization, indicating that they may have originated from more local sources, microplastic fibers were found in reasonably steady levels even in the least human-affected salt marshes, implying that their roots were more diffuse—and that any mitigation measures, according to Lloret, would have to take place at the state or regional level rather than at the local level.
“Fibers are presumably produced more locally and transported more efficiently by wind or tides, so their quantities are more homogeneous,” Lloret explains.
The authors of the research state that they were unable to evaluate plastic particles smaller than 250 microns due to technical limitations. They also failed to determine the chemical makeup of the particles, which might lead to the misidentification of non-plastic fibers as microplastic fibers, according to Susanne Brander, an ecotoxicologist at Oregon State University who was not involved in the study.
The thought that fibers are being moved about on a global or regional basis, however, struck Brander the most. In an email to Popular Science, Brander stated, “The finding has me contemplating how we may begin to lessen global pollution from fibers.” We need to stop them at the source, starting with our washers and dryers, and remove them from agricultural biosolids before they are applied.
According to the authors, this study is only the beginning of a lengthy line of inquiries into the interaction between microplastics and salt marsh ecosystems.
“There is a lot of opportunity for contact with the creatures and plants that live there is huge,” says Lloret