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Investigating the potential uptake of microplastic-derived carbon into a boreal lake food web using carbon-13 labelled plastic
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In one of the most rigorous field experiments of its kind, scientists added isotopically labelled polystyrene microplastics to an enclosed section of a Canadian lake and tracked whether plastic-derived carbon entered the food web over four months. They found no measurable leaching of carbon from the plastics into the water or into plankton and algae, suggesting that under natural lake conditions, polystyrene microplastics degrade extremely slowly. This is reassuring in one respect — carbon isn't quickly moving from plastics into aquatic food chains — but it also means microplastics persist in the environment for very long periods.
Microplastics degrade slowly over time, leaching carbon (C) that could be subsequently incorporated into aquatic food webs. Current estimates of microplastic degradation vary, and little is known about microplastic-derived C fate under natural environmental conditions. To investigate whether microplastics leach C that is subsequently incorporated into aquatic food webs, we added isotopically enriched microplastics to Lake 378 at the Experimental Lakes Area in Ontario, Canada. In an ∼1100 L limnocorral (in situ open-bottom enclosure), we added 99% 13 C-labelled polystyrene (8–216 µm in longest dimension) at a nominal concentration of 3268 particles/L. A second limnocorral without microplastics served as a negative control. Monthly measurements of δ 13 C-DIC and δ 13 C-DOC in filtered water revealed no detectable leaching of 13 C from the plastic. Compound-specific isotope analysis of δ 13 C in amino acids of bulk plankton and periphyton revealed a slight (0.5‰) enrichment in 13 C, within the range of natural variability for these organisms. Under the natural conditions of temperate oligotrophic lakes, degradation of microplastics is likely a very slow process that was not possible to detect in this 4-month experiment. Future studies should focus on assessing degradation of microplastics under realistic field scenarios to improve estimates of degradation pathways and associated time scales.
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Researchers used carbon-13-labeled experiments to trace how terrestrial leaves, lignin, and polystyrene microplastics are processed through a four-level aquatic food web from microbes to fish. While microbes could synthesize amino acids and lipids from plant-derived carbon, they produced far fewer nutritional biomolecules from polystyrene, and the resulting molecules were still incorporated into zooplankton and fish tissues. The study shows that plastic carbon can move through food webs and become part of animal body tissues, though at reduced nutritional value, raising concerns about the long-term health of aquatic ecosystems and the quality of fish consumed by humans.
Biodegradation of microplastic in freshwaters: A long‐lasting process affected by the lake microbiome
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Researchers used carbon-13-labelled polyethylene microplastics and stable isotope analysis to investigate biodegradation in freshwater lake environments, finding that while the lake microbiome can degrade polyethylene, the process is extremely slow and affected by the composition of the microbial community.
Tracing the fate of microplastic carbon in the aquatic food web by compound-specific isotope analysis
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Researchers used compound-specific stable isotope analysis with fully labelled carbon-polyethylene microplastics to trace the fate of microplastic carbon through aquatic food webs, demonstrating that microbial activity is required for breakdown and assimilation of microplastic carbon.
Natural abundance δ13C constraints on the detection of microplastic-derived carbon in freshwater environments
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Researchers evaluated whether stable carbon isotope measurements could be used to trace microplastic-derived carbon in freshwater food webs. They found that while one algae species showed significant isotopic shifts when exposed to microplastics, these changes reflected physiological stress rather than actual incorporation of plastic carbon. The study concludes that natural carbon isotope methods have limited practical utility for detecting microplastic signals in freshwater ecosystems under realistic conditions.
Decomposition rate and biochemical fate of carbon from natural polymers and microplastics in boreal lakes
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Researchers investigated the microbial decomposition rates and biochemical fate of several natural polymers (lignin, cellulose, hemicellulose) and microplastics as carbon sources in boreal freshwater lakes, finding that natural recalcitrant polymers and synthetic microplastics differ substantially in their rates of microbial mineralisation and incorporation into aquatic food webs.
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