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Biofilm growth on buoyant microplastics leads to changes in settling rates: Implications for microplastic retention in the Great Lakes
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Researchers measured biofilm-induced density changes and sinking rates for buoyant polyethylene microplastics in Great Lakes water, finding that biofouling caused particles to sink within days to weeks, with implications for predicting where microplastics accumulate in large lake systems.
Buoyant microplastic pollution disperses widely from sources via strong wind-driven water currents in lakes and oceans. This ability for dispersal depends critically upon the particle's density, which can change over time due to microbial growth (biofilm). This study quantifies biofilm-induced sinking rates of irregularly-shaped polypropylene granules (~125-2000 μm) via ex-situ experiments emulating a Great Lakes freshwater environment. Biofilm development increases particle density and lowers microplastic rise velocities, eventually causing sinking. We observed sinking for 100% of small and intermediate microplastics, and 95% of large microplastics. Under constant environmental conditions, sinking onset was observed sooner for smaller particles (~125-212 μm, 18 days) than for larger particles (~1000-2000 μm, 50 days). Differences in settling onset would lead to size-fractionation of particle sedimentation, whereby smaller particles are deposited closer to their sources relative to larger particles. Our study demonstrates a novel mechanism by which buoyant microplastics can selectively sink from the lake surface.
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Biofilm-induced sinking of buoyant microplastics in a freshwater environment
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Researchers demonstrated experimentally that biofilm growth on buoyant microplastic particles caused them to sink from the surface of a freshwater lake and accumulate in sediments. The experiment directly confirmed the biofouling-induced sinking mechanism as a key process controlling the vertical distribution of microplastics in lake water columns.
Sinking of microbial-associated microplastics in natural waters
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Researchers investigated how microbial biofilm colonization of microplastics affects their buoyancy and sinking behavior in natural waters, finding that biological ballasting from attached microorganisms can significantly increase particle density and promote vertical transport toward sediments. The results suggest that biofouling is a key mechanism driving the removal of microplastics from surface waters.
Microplastic-specific biofilm growth determines the vertical transport of plastics in freshwater
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Researchers studied biofilm growth on five different microplastic polymer types in freshwater over 63 days to understand how biological colonization affects sinking behavior. The study found that biofilm growth is polymer-specific and can significantly alter the density of microplastic particles, which in turn determines whether they sink or float, influencing their vertical transport through freshwater systems.
Experimental assessment of settling velocity of pristine and biofouled microplastics
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Researchers experimentally measured how biofouling alters the settling velocity of microplastic particles, finding that biofilm growth on buoyant plastic fragments caused them to sink more rapidly. The results demonstrate that biological colonization of plastic surfaces is a key mechanism driving the vertical transport of microplastics from surface water to the seafloor.
Effects of biofilm colonization on the sinking of microplastics in three freshwater environments
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A 44-day freshwater incubation experiment showed that biofilm colonization on PET, PP, and PVC microplastics promoted sinking in three Chinese water bodies, with biomass and chlorophyll levels varying by environment and influencing the rate of buoyancy change.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.