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Impact of Microplastics on Microbial Community Composition and Diversity in Surface Flow Constructed Wetland Sediments
Summary
A study of conventional PVC and biodegradable PLA microplastics in constructed wetland sediments found both types altered microbial diversity and community composition, with PVC enriching denitrifying bacteria and PLA promoting methanogenic pathways at concentrations as low as 1%. These microbial shifts in wetland sediments could disrupt nitrogen and carbon cycling in ecosystems that serve as critical water quality filters.
Accumulation of microplastics (MPs) in sediments threatens wetland ecosystems, yet the impacts of distinct microplastic types on sediment microbial community and biogeochemical cycling remain poorly understood. This study investigates the impacts of conventional polyvinyl chloride (PVC) and biodegradable polylactic acid (PLA) MPs, at concentrations of 0%, 1%, and 5%, on microbial community composition and diversity in constructed wetland (CW) sediments. Both PVC and PLA MPs increased microbial α-diversity (Shannon index up to 6.4%) but reduced evenness (Simpson index decreased by 40.3%) and altered β-diversity (p < 0.05). Microplastics decreased the abundance of bacteria while increasing that of archaea and eukaryotes. PVC MPs significantly enriched Acidovorax and Magnetospirillum genera associated with denitrification, while PLA MPs significantly enriched Anaerolinea in denitrification and Clostridium in methanogenesis. Results revealed that 5% microplastic exposure significantly increased the abundance of methanogenic enzymes, particularly under PLA exposure. PVC MPs increased the abundance of denitrification enzymes, while PLA MPs promoted the abundance of amino acid metabolism enzymes. This study offers a novel analysis of the impacts of different microplastic types and concentrations on microbial community composition and diversity in wetland sediments, providing valuable insights into the ecological risks posed by MPs in wetland ecosystems and emphasizing the need for further research on their environmental impacts.