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Acidification reshapes plastisphere communities to sustain potassium-stimulated N2O emissions under warming
Summary
Microbes growing on plastic waste in soil and water — a phenomenon scientists call the "plastisphere" — can produce nitrous oxide, a greenhouse gas roughly 300 times more potent than CO2, and this problem gets worse when fertilizer runoff, warming, and acidic conditions combine. Compostable "biodegradable" plastic actually hosted more of these gas-producing microbes than regular plastic, suggesting it's not automatically the eco-friendlier choice. While this study focuses on climate impact rather than direct human health effects, it highlights an overlooked way that plastic pollution, far
The plastisphere is a novel anthropogenic habitat in the global nitrogen cycle, yet how agricultural nutrient pollution, acidification, and warming combinedly affect its nitrous oxide (NO) fluxes remains unknown. We hypothesized that these stressors amplify emissions from plastic biofilms. A factorial mesocosm experiment exposed biodegradable (PLA) and non-biodegradable (PE) plastics to potassium (K-70 mg/L), acidification (pH 6.0, 6.5), and warming (23°C, 28 °C) under hypoxic conditions, using inhibitors and genomic profiling to identify pathways. PLA consistently sustained higher NO emissions than PE, dominated by bacterial denitrification. Potassium and warming elicited a synergistic response, increasing NO flux by 58%. While acidification combined with potassium and warming suppressed key functional genes (nirS, nosZ), it selected stress-tolerant consortia, including resilient nirK-type denitrifiers, that sustained the genetic potential for NO production. This community adaptation and reduced NO reduction capacity (lower nosZ) explain persistent emissions under acidic conditions. Abiotic chemo-denitrification occurred but was an order of magnitude slower than in pure chemical systems. Polymer-specific restructuring occurred, with PLA supporting more diverse consortia and higher genetic potential for nitrogen transformations. Three-way ANOVA confirmed that potassium × warming synergy is significantly modulated by pH (p < 0.001). These findings establish the plastisphere as a significant, unquantified NO source, creating a feedback loop between plastic pollution, agriculture, and climate change, necessitating its inclusion in global nitrogen and climate models.