Surface dynamics of newly released microplastics during early-stage aging in coastal water: Physicochemical property alterations and microbial community successions

Predicting the environmental fate of marine microplastics (MPs) requires a process-based understanding of surface transformations upon exposure. However, current knowledge relies heavily on laboratory simulations or isolated physicochemical/microbial perspectives. Here, we conducted in situ aging of four globally abundant MPs-polystyrene (PS), polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET)-in coastal waters within one month. Alterations in surface micro-morphology, nanomechanical properties, chemical functionalization, and elemental composition, alongside prokaryotic and eukaryotic community successions, were analyzed using a multi-dimensional framework. Scanning electron microscopy and attenuated total reflectance Fourier transform infrared spectroscopy revealed progressive surface microscale modifications and oxidation across all polymers. Concurrently, atomic force microscopy and X-ray photoelectron spectroscopy captured a volatile boundary layer, marked by fluctuating nanoscale roughness, adhesion, and stiffness, and elemental fluxes, reflecting dynamic biofilm attachment-detachment cycles. High-throughput 16S/18S rRNA sequencing demonstrated that plastisphere communities were distinct from ambient seawater, anchored by a conserved, hyper-diverse prokaryotic core alongside a fluctuating, less diverse eukaryotic assembly. Network analysis revealed highly cooperative structures with polymer-specific topologies, displaying a dense unified core module for PET but isolated, niche-separated sub-modules for PP that recruited specialized taxonomic cohorts. Polymer chemistry acted as a selective ecological filter for prokaryotes on PS, PP, and PET, but functioned as a featureless "blank slate" on PE. Conversely, all MP substrates served as isolated physical "islands" for eukaryotes, where spatial fragmentation and dispersal bottlenecks overrode chemical selection, driving stochasticity-dominated assembly. This work resolves early-stage marine plastisphere dynamics, providing a realistic framework for assessing long-term MP ecological risks.