Substrate-driven microbial diversity and functional potential of plastisphere biofilms in a dynamic coastal ecosystem of northeastern Taiwan

Increasing plastic waste in marine ecosystems has led to the emergence of plastic-associated microbial communities, i.e., plastisphere biofilms. Understanding plastisphere ecology and its environmental impacts is critical for addressing challenges posed by plastic pollution. This study investigated microbial community structure and predicted functions associated with floating microplastics natural wood debris, and surface seawater collected from ten sites across Yilan Bay, northeastern Taiwan, an area influenced by the Kuroshio Current. Using full-length 16 S rRNA gene sequencing via Oxford Nanopore Technologies, we observed that microplastics harbor unique and highly diverse microbial communities, exhibiting significantly higher diversity compared to the surface seawater communities (p < 0.05). In contrast, microbial communities on wood displayed diversity levels comparable to those of the surrounding seawater. Although microbial communities on plastic and wood surfaces shared similar major taxa, the exhibited distinct association patterns, underscoring the ecological significance of substrate type. Co-occurrence network analysis revealed distinct microbial interactions on plastics, with substrate-specific hub genera in plastisphere biofilms. Predicted functional profiles suggest that microplastic-associated communities may support functions related to nitrogen and sulfur cycling, and hydrocarbon degradation. Notably, we detected the presence of putative pathogenic taxa in the plastisphere, raising concerns about its potential role as a mobile reservoir with implications for environmental and public health. These findings enhance our understanding of plastisphere dynamics in marine ecosystems and emphasize the need for effective management strategies to mitigate the environmental impact of plastic waste.