Hidden sinks of microplastics and nanoplastics in aquatic environments: The EPS-mediated eco-corona perspective

Microplastics and nanoplastics (MNPs) levels in surface waters of aquatic systems are substantially lower than expected from estimated inputs. This "missing plastic" phenomenon has drawn attention to systematic gaps in how detect and classify particle states. Extracellular polymeric substances (EPS) mediated ecological corona (eco-corona) formation represents an interface transition. This process changes MNP surface properties and environmental behavior, yet it has received less systematic attention than biofouling, marine snow incorporation, and physical transport. This critical review examines how EPS governs the surface properties and interactions of MNPs. As a ubiquitous constituent of eco-coronas, EPS also shapes particle aggregation, vertical transfer, and bioavailability. EPS encounters MNPs through charge screening, polymer bridging, and gel-network entrapment. The eco-corona formation constitutes the true interface transformation. This transition alters colloidal stability and buoyancy. It also promotes heteroaggregation and co-settling, shifting MNPs from surface waters toward deeper waters and sediments. While this EPS-mediated pathway operates alongside other recognized processes, it represents a mechanistically distinct and being neglected to the apparent surface mediator of MNPs. Consequently, water quality approaches and risk assessments that rely exclusively on surface free particle levels may systematically underestimate actual MNP exposure and ecological hazards. This paper establishes a framework that links the molecular interface mechanism to macro-environmental behavior. It demonstrates that EPS-mediated eco-corona formation does not simply change risk; instead, it shifts the exposure context and redistributes MNPs across environmental compartments. These insights provide a foundation for refining risk assessments of MNPs in aquatic systems.