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Stable Isotopic and Metagenomic Analyses Reveal Microbial-Mediated Effects of Microplastics on Sulfur Cycling in Coastal Sediments
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This study investigated how microplastics affect sulfur cycling in coastal mangrove sediments, an important process for marine ecosystem health. Biodegradable plastics actually increased sulfur-related bacterial activity more than conventional plastics, suggesting they may have unintended environmental effects. The findings show that microplastic pollution can disrupt fundamental chemical cycles in coastal environments, which could have cascading effects on water quality and the marine food web.
Microplastics are readily accumulated in coastal sediments, where active sulfur (S) cycling takes place. However, the effects of microplastics on S cycling in coastal sediments and their underlying mechanisms remain poorly understood. In this study, the transformation patterns of different S species in mangrove sediments amended with different microplastics and their associated microbial communities were investigated using stable isotopic analysis and metagenomic sequencing. Biodegradable poly(lactic acid) (PLA) microplastics treatment increased sulfate (SO42-) reduction to yield more acid-volatile S and elementary S, which were subsequently transformed to chromium-reducible S (CRS). The S isotope fractionation between SO42- and CRS in PLA treatment increased by 9.1‰ from days 0 to 20, which was greater than 6.8‰ in the control. In contrast, recalcitrant petroleum-based poly(ethylene terephthalate) (PET) and polyvinyl chloride (PVC) microplastics had less impact on the sulfate reduction, resulting in 7.6 and 7.7‰ of S isotope fractionation between SO42- and CRS from days 0 to 20, respectively. The pronounced S isotope fractionation in PLA treatment was associated with increased relative abundance of Desulfovibrio-related sulfate-reducing bacteria, which contributed a large proportion of the microbial genes responsible for dissimilatory sulfate reduction. Overall, these findings provide insights into the potential impacts of microplastics exposure on the biogeochemical S cycle in coastal sediments.
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Researchers used a 112-day microcosm experiment to show that three common microplastics — PLA, PE, and PS — each distinctly rewire sulfur-cycling microbial communities in seagrass sediments, shifting metabolism from biosynthetic toward dissimilatory energy-generating pathways and amplifying sulfide stress in ways that could undermine carbon burial and ecosystem resilience.
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Researchers found that polylactic acid (PLA) microplastics in mangrove sediments accelerated the breakdown of dissolved organic carbon by boosting sulfate-reducing bacteria activity. Millimeter-sized PLA particles had a greater effect than micrometer-sized ones, fundamentally altering carbon and sulfur cycling in these important coastal ecosystems. This matters because mangrove sediments are major carbon stores, and microplastic contamination could speed up carbon release, worsening climate change.
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This study examined how polystyrene and polyphenylene sulfide microplastics affect microbial-mediated sulfur transformations in flooded soils. Researchers found that microplastic contamination significantly altered the microbial community structure involved in sulfur cycling, suggesting that microplastics could disrupt important nutrient processes in waterlogged agricultural soils.
Subtle biogeochemical consequences of biodegradable and conventional microplastics in estuarine blue carbon systems
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Researchers conducted field experiments exposing mangrove ecosystems to conventional and biodegradable microplastics for up to 100 days. While overall microbial community composition remained stable, the biodegradable microplastics temporarily disrupted key nutrient cycling processes for carbon, nitrogen, and phosphorus. The findings suggest that even in resilient blue carbon ecosystems, biodegradable plastics can cause subtle but measurable changes to biogeochemical functions.
Mangrove degradation retarded microplastics weathering and affected metabolic activities of microplastics-associated microbes
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Microplastic weathering was slower in degraded mangrove sediments than in intact mangroves, with degradation also altering the composition and metabolic activity of microplastic-associated microbial communities. The findings suggest mangrove ecosystem health influences how rapidly microplastics degrade and what ecological roles microplastic-associated microbes play in these coastal environments.
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