New MIT research reveals that natural biofilms—slimy coatings left by microorganisms—play a surprising role in microplastic pollution, dictating where these particles settle or vanish downstream.
Key Points at a Glance
- Biofilms reduce microplastic accumulation in riverbeds and coastal areas
- Particles are more easily resuspended in sediment infused with biofilms
- Findings offer new tools for predicting and managing microplastic hotspots
- Research may guide environmental remediation efforts more effectively
They’re invisible to the naked eye, yet everywhere—from our oceans and rivers to the insides of our bodies. Microplastics, the byproducts of a world dependent on plastic, have become a persistent environmental threat. But if we can’t eliminate them overnight, perhaps we can at least understand where they go. Now, a breakthrough study from MIT sheds new light on precisely that mystery—and it all comes down to slime.
Published in the journal Geophysical Research Letters, the study shows that biofilms—those thin, sticky layers made by bacteria, algae, and fungi—dramatically reduce microplastic accumulation in aquatic sediments. Led by MIT postdoc Hyoungchul Park and professor Heidi Nepf, the research is the first to quantify how these natural biological coatings influence microplastic transport and deposition.
In a meticulously controlled lab setup, researchers simulated stream environments using flow tanks lined with sandy sediment. In some trials, they added biofilm-mimicking substances to simulate natural conditions more accurately. Water infused with tiny fluorescent plastic particles was run through the tanks, allowing precise tracking of where—and how much—plastic accumulated.
The results? Microplastic particles settled more readily in clean, bare sand. But when biofilms were present, these sticky coatings filled the spaces between sand grains, preventing particles from lodging deep into the sediment. Instead, the plastics remained more exposed at the surface—and were far more likely to be swept away by flowing water.
“These biological films fill the pore spaces between sediment grains,” explains Park. “That makes deposited particles more exposed to flow forces, and easier to resuspend.”
The implications are striking. In areas rich with biofilms—think muddy mangrove forests or algae-heavy riverbeds—microplastics may pass through with little accumulation. By contrast, sandy or gravelly environments without biofilms may act as hotspots, trapping significant amounts of plastic debris over time.
This research provides a practical lens for environmental scientists. “It gives guidance to where you should go to find more plastics versus less,” says Nepf. Field researchers can use these findings to better focus sampling, cleanup, and remediation efforts—prioritizing sandy shores over muddy deltas, for example.
The study also hints at unexpected solutions. Encouraging biofilm growth or strategic re-vegetation in vulnerable ecosystems might not just aid habitat restoration—it could also help sweep harmful plastics downstream where they might be easier to capture or disperse.
“It highlights the powerful role of biological and physical features in shaping particle transport,” says Isabella Schalko, a scientist at ETH Zurich, unaffiliated with the study. With restoration measures in mind, managing biofilm dynamics could become a novel tool in the fight against microplastic pollution.
Backed by Shell International Exploration and the MIT Energy Initiative, this research blends environmental engineering with ecology in a way that could reshape how we manage pollution at the tiniest scales. It’s not just about the plastic—it’s about the microscopic ecosystems beneath our feet, silently guiding where our waste ends up.
Source: MIT News
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