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Differential responses of rare and abundant taxa in the plastisphere of biodegradable and non-biodegradable microplastics in soil
Summary
"Biodegradable" plastics are often marketed as the eco-friendly swap for regular plastic, but this study found they actually disturb soil microbes more than conventional plastic does—especially rare microbe species that quietly keep soil ecosystems stable and resilient. Since healthy soil microbes support the food we grow and help break down pollutants, this suggests biodegradable plastics aren't automatically the safer choice for soil health, and more testing is needed before we assume they're better for the environment (and ultimately, us).
Biodegradable microplastics are increasingly advocated as sustainable alternatives to conventional non-biodegradable microplastics to mitigate soil pollution. However, the distinct ecological consequences of biodegradable microplastics on the soil plastisphere, particularly regarding the assembly and function of rare versus abundant microbial taxa, remain poorly understood. Here, we investigated the microbial community structure, co-occurrence networks, and functional potential in the plastisphere of biodegradable PBAT/PLA and non-biodegradable PE microplastics compared to bulk soil. Our results revealed that the plastisphere constitutes a unique niche that selectively filters microbial communities, with PBAT/PLA plastisphere exerting a significantly stronger selection pressure than PE plastisphere. While abundant taxa dominated the biomass, rare taxa played a critical role in maintaining community structure, serving as the primary network hubs and reservoirs of functional diversity. Critically, we observed that PBAT/PLA microplastic exposure led to increased network fragility and a reduction in the abundance of key functional genes within the rare biosphere. These findings suggest that although biodegradable microplastics promote distinct microbial assemblages, they may compromise soil functional redundancy and ecosystem resilience. This study highlights the need to consider the stability of rare microbial sub-communities in the ecological risk assessment of plastic alternatives.