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Coupling of sulfate reduction and dissolved organic carbon degradation accelerated by microplastics in blue carbon ecosystems
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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.
Microplastics have increasingly accumulated in sulfate- and organic matter-rich mangrove ecosystems, yet their effects on microbially mediated carbon and sulfur cycling in sediments remains poorly understood. In this study, we performed a 70-day anaerobic microcosm experiment to examine the effects of polylactic acid (PLA) microplastics with different sizes on sulfate reduction and dissolved organic carbon (DOC) degradation in mangrove sediments. Our results demonstrated that millimeter-scale PLA (mm-PLA) more effectively enhanced sulfate reduction, sulfur isotope fractionation, reduced sulfide production, and carbon dioxide (CO) emission compared to micrometer-scale PLA (m-PLA). These results suggested that mm-PLA had a more pronounced impact on the carbon and sulfur cycles. Integrated 16S rRNA gene amplicon sequencing and metagenomic analyses revealed that mm-PLA preferentially enriched key functional microorganisms, including acetate-producing bacteria (e.g., Acetobacteroides), completely oxidizing sulfate-reducing bacteria (e.g., Desulfobacter), and incompletely oxidizing sulfate-reducing bacteria (e.g., Desulfobulbus). These microorganisms exhibited higher abundances and greater genetic potential for carbon metabolism and sulfate reduction under mm-PLA treatment. Their relative abundances showed positive correlations with sulfate reduction rates, sulfur isotope fractionation, and CO emission, identifying them as crucial drivers of coupled carbon-sulfur cycling. Furthermore, the synergistic interactions among Acetobacteroides, Desulfobacter, and Desulfobulbus facilitated the oxidation of sediment-derived DOC, highlighting significant implications for carbon sequestration in blue carbon ecosystems.
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Effects of microplastics on carbon release and microbial community in mangrove soil systems
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Researchers tested how microplastics affect carbon release and microbial life in mangrove soils at different depths. They found that while topsoil was largely unaffected, deeper soil layers released significantly more carbon dioxide when microplastics were present, particularly biodegradable types like polylactic acid. The study suggests that microplastic contamination in mangrove ecosystems could accelerate carbon loss from deeper soils by disrupting microbial communities and worsening nitrogen limitations.
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.
Depth-dependent response of soil microbial community and greenhouse gas efflux to polylactic acid microplastics and tidal cycles in a mangrove ecosystem
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Researchers found that biodegradable plastic (PLA) microplastics in mangrove soil increased the release of greenhouse gases, especially carbon dioxide and methane, from deeper soil layers. The microplastics altered soil bacterial communities in ways that boosted methane-producing organisms. This finding is important because biodegradable plastics are often marketed as environmentally friendly, but they may still harm ecosystems by accelerating carbon release from soils.
Microplastics drive the reconfiguration of microbial sulfur cycling pathways in seagrass bed 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.
Microplastics trigger sediment organic carbon pools stabilization pathways: Evidence from microbial mediated DOM turnover
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Lab sediment mixed with two types of plastic (polyethylene and polylactic acid) for 100 days released more carbon dioxide and methane and changed the sediment's dissolved organic matter and microbial communities. Aged polylactic acid caused the biggest changes, increasing sediment oxidation and altering bacterial, fungal and archaeal community networks involved in carbon breakdown.
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