Perspective into bio-fouled microplastic behaviour, transportation and characterization in water bodies

Biofouling on microplastics (MPs) has emerged as a key driver shaping their environmental behavior, yet its mechanisms and implications remain insufficiently resolved. This review synthesizes current knowledge on the formation, development, and ecological significance of the plastisphere, which is the complex biofilm community that colonizes MPs. This review examines how biofouling alters MP physicochemical properties, including density, surface charge, hydrophobicity, and roughness, leading to profound changes in transport dynamics, vertical flux, and long-term fate in aquatic systems. The review further analyzes the mechanisms of biofilm development, macrofouling contributions, and biofilm-mediated interactions with chemical contaminants, highlighting how biofouled MPs become reactive vectors for metals, pathogens, and hydrophobic organic pollutants. Key environmental and polymer-specific factors governing biofouling are evaluated alongside recent advances in microscopy, spectroscopy, and molecular tools for biofilm characterization. Persistent gaps including inconsistent methodologies and the absence of standardized protocols are identified as major constraints to cross-study comparability. By integrating insights from ecology, materials science, and environmental engineering, this review outlines a forward-looking research and methodological roadmap to improve prediction, detection, and mitigation of biofoul-driven transformations of MPs. Overall, this work highlights biofouling as a critical but under-addressed determinant of MP persistence and ecological risk in freshwater and marine environments.