Plastisphere provides a unique ecological niche for microorganisms in Zostera marina seagrass meadows

Abstract Seagrass meadows are renowned for their associated ecosystem services and carbon sequestration capacity, with microorganisms playing a crucial role. However, the invasion of microplastics may disrupt these processes. Here, we conducted a one-month in-situ incubation of three prevalent types of microplastics in the seagrass meadow of Swan Lake, China. The results showed significant differences in microbial communities between the plastisphere and natural matrices. Cyanobacteria exhibited a strong preference for polyethylene terephthalate, and microplastic shape and their contact area with water may be key factors in shaping microbial communities. Meanwhile, microplastic invasion can shift carbon- and nitrogen-fixing microbes and related genes, thereby changing seagrass meadows’ carbon and nitrogen cycles. This may impact the carbon sequestration capacity of seagrass meadows and pose potential risks of water blooms. Additionally, the potential ecological risks posed by the large number of resistance genes adsorbed by microplastics in the ecosystem are also worthy of attention.