Researchers estimate that there are around 400 billion microplastic fibers floating on the surface of Frenchman Bay, situated next to Bar Harbor and Acadia National Park in Maine, as well as several related rivers and estuaries where fresh river water mixes with the ocean’s saltwater. On average, the watershed holds about 1.8 microplastic fibers per liter of water. Additionally, the team studied how these microplastics moved through the watershed by collecting water samples from nine locations on Mount Desert Island, mainly within Bar Harbor.
Frenchman Bay, stretching over 98 square miles and dotted with 39 islands, is crucial for birds, fish, lobstermen, and outdoor enthusiasts along the shores of Acadia National Park, Bar Harbor, and the Schoodic Peninsula. However, researchers from the University of Maine have found that significant microplastic pollution is also present in Frenchman Bay and its tributaries.
A recent study published in Environmental Engineering Science discloses that an estimated 400 billion microplastic fibers are floating in Frenchman Bay and its connected rivers and estuaries where freshwater meets salty seawater, with an average of 1.8 fibers per liter of water in the watershed.
“Think about your 32-ounce water bottle. If you filled it with water from Frenchman Bay, you’d find about two microplastic fibers inside. Now, consider how many bottles would fit in the vast expanse of Frenchman Bay; that’s a massive amount of microplastics,” said Grace Johnson, the study’s lead author and a master’s student in civil and environmental engineering. Johnson worked alongside other UMaine students and faculty and researchers from Notre Dame and Valparaiso University in Indiana.
Microplastics, which are smaller than five millimeters, can be easily ingested by both humans and animals. Trillions of these particles have been detected in rivers, lakes, and oceans globally. They can result from larger plastic items breaking down and from tiny plastic beads used in personal care products, according to the National Oceanic and Atmospheric Administration (NOAA). These microplastics can cause health problems in animals, impacting digestion and reproduction, and certain chemicals associated with them are linked to hormonal disruptions and cancer risks in humans, according to the U.S. Geological Survey. They can also absorb and carry other harmful toxins, such as a group of substances known as PFAS, that contaminate water sources.
The researchers conducted two water sampling campaigns throughout 2022 and 2023. They collected 129 samples using glass mason jars from the bay, rivers, and estuaries over 17 weeks while on a boat. Microscopes were employed to identify the microplastic fibers in the samples and analyze their characteristics by measuring their light signatures — the colors and wavelengths of light that the fibers reflect or absorb.
Microplastic concentrations were highest on average in the bay itself, followed by the connected rivers and then the estuaries. Egypt Stream in Franklin had the highest concentration of microplastics among the rivers, followed by Kilkenny Stream in Hancock and the Union River, which flows through Ellsworth. For estuaries, the one between Stave Island and Gouldsboro showed the highest average, followed by the Sullivan Estuary, draining Egypt Bay, and Jordan River flowing between Lamoine and Trenton.
“What surprised me was that even in the open ocean, we found one to two microplastic fibers in nearly every liter we sampled,” said Onur Apul, co-author of the study, Johnson’s advisor, and assistant professor of environmental engineering. “The varying quantities we’re observing in nature suggest that we’ve inadvertently created a new environmental realm — the ‘microplastisphere’ — during the short time that humans have inhabited this planet.”
The research team also examined how microplastics were transported throughout the watershed by sampling water at nine locations on Mount Desert Island, particularly in Bar Harbor. In 2023, they collected samples from the culvert at Grant Park, directly across from Bubble Rock; several sites at Kebo Stream; and multiple locations around Cromwell Brook, including the wastewater treatment facility and a culvert for the transfer station. Sampling was conducted on clear days as well as during rainy weather when culverts released stormwater.
The highest concentration of microplastics was found at the Grant Park culvert, at 15 fibers per liter, followed by the wastewater treatment plant, the transfer station, and other sampling locations along Cromwell Brook and Kebo Stream. Overall, the average microplastic concentrations at these sites surpassed those found in the estuaries, rivers, and Frenchman Bay.
Based on their findings, researchers concluded that microplastics are being carried from land into rivers and estuaries and eventually into Frenchman Bay, where weaker currents can cause the fibers to remain for extended periods. The research team proposes further studies on pollution in the bay and nearby watershed to explore ways to reduce the spread of microplastics.
“Once microplastics are distributed in Frenchman Bay, there is no way to remove them, posing risks to both marine life and humans. Fish and other marine creatures can ingest these particles, which can then transfer to humans who consume the fish. Therefore, as a society, we must reduce plastic waste that can contaminate the ocean,” emphasized Johnson.
Alongside Johnson and Apul, additional researchers involved in this project include UMaine graduate students Taylor Bailey, Dilara Hatinoglu, and Bea Van Dam; faculty members Lauren Ross and Sean Smith; Ph.D. student Ozioma Nwachukwu; associate professor Kyle Doudrick from Notre Dame; and professor Julie Peller from Valparaiso University.
“We discover microplastics not just in fish tissue, but also in bird droppings, on beaches, in our drinking water, and even in human organs such as the brain and placenta,” Apul added. “We advocate for ‘mindful usage’ of plastics, as they serve beneficial purposes, like in medical applications or food packaging; however, many are used carelessly and disposed of improperly. For instance, a plastic coffee stirrer is used for just a few seconds. My second recommendation is to promote pollution prevention through sustainable policies that prioritize safety.”