Environmental fate and biogeochemical impacts of microplastics on phosphorus cycling across aquatic interfaces

Microplastics (MPs) have gained increasing scientific attention for their complex and far-reaching impacts on aquatic ecosystems, particularly through their interactions with elemental biogeochemical cycles. As an essential nutrient, phosphorus (P) plays a pivotal role in sustaining biological productivity in aquatic environments, yet its transport and fate are substantially altered by the presence of MPs. This review synthesizes findings from 38 peer reviewed studies to elucidate how MPs influence P cycling at aquatic interfaces. MPs serve as dynamic participants in P cycling. They affect P dynamics through dose dependent effects, physical interference, and both direct and indirect biochemical pathways, with incompletely degraded MPs having more pronounced impacts. By altering habitat conditions and offering new surfaces for colonization, MPs reshape microbial communities and the expression of functional genes involved in P metabolism. Modifications in surface reactivity, ion exchange equilibrium, and redox processes further influence the migration and transformation of P. These interactions are largely governed by the physicochemical properties of MPs and ambient environmental conditions, with particle size and abundance identified as key determinants of total phosphorus in natural waters. Although laboratory experiments have yielded valuable mechanistic insights, they frequently fail to replicate in situ complexity, underscoring the need for more realistic, long-term studies. This review also highlights potential mitigation strategies, including biodegradable MPs, microbial remediation, and ecosystem-based engineering. By addressing a critical research gap, it emphasizes the importance of integrating MPs into nutrient cycling frameworks and aquatic ecosystem management.