Microplastic dilemma: Assessing the unexpected trade-offs between biodegradable and non-biodegradable forms on plant health, cadmium uptake, and sediment microbial ecology

Despite extensive substitution of biodegradable plastics (BPs) for conventional plastics (CPs), research on their environmental ecological consequences as microplastics (MPs) is scarce. This study aimed to fill this gap by investigating the impacts of six prototypical MPs (categorized into BMPs and CMPs) on plant growth, cadmium (Cd) translocation, and bacterial communities in contaminated sediments. Results showed both BMPs and CMPs hindered plant development; yet interestingly, BMPs provoked more pronounced physiological and biochemical changes alongside increased oxidative stress due to reactive oxygen species accumulation. Notably, most MP types promoted the absorption of Cd by plant roots potentially via a "dilution effect". BMPs also induced larger shifts in soil microbial metabolic functions compared to CMPs. Ramlibacter was identified as a key biomarker distinguishing BMPs from CMPs, with link to multiple N metabolic pathways and N assimilation. This study offers novel insights into intricate biochemical mechanisms and environmental chemistry behaviors underpinning MP-Cd interactions within the plant-microbe-sediment system, emphasizing BMPs' higher potential ecological risks based on their significant effects on plant health and microbial ecology. This work contributes to enhancing the comprehensive understanding of their ecological implications and potential threats to environmental security.