Ingestion and digestion by the freshwater snail Pomacea canaliculata drive microplastic surface transformations and virus-mediated plastisphere functional shifts

Microplastics are widely present in aquatic animals, but the effects of animal feeding behavior on their surface properties, particularly plastisphere functionality and viral community remain poorly understood. This study investigated the effects of freshwater apple snails ingesting polystyrene (PS) and expanded polystyrene (EPS) microplastics through three microcosm experiments, quantifying ingestion rates, characterizing surface transformations, and profiling plastisphere microbiota. Snails retained ∼2-45 microplastic particles in their gut, with a residence time of ∼48 h. Digestion deformed EPS and induced surface oxidation of both PS and EPS, generally reducing plastisphere antibiotic resistance genes (ARGs; by ∼30 %) and methanogenesis pathways (by ∼85 %), while enhancing denitrification pathways (by ∼80 %) and human health resistome risk (HHRR; by ∼80 %) from EPS. Notably, digestion affected plastisphere viruses more strongly than bacteria, highlighting viruses as key drivers of digestion-induced plastisphere functional shifts. Plastisphere temperate viruses carried more ARGs, correlating with elevated resistome risks, whereas virulent viruses harbored more auxiliary metabolic genes (AMGs), correlating with reduced PS-degrading bacteria. Both viral lifestyles were differentially linked to carbon, nitrogen, and sulfur cycling. Overall, this study demonstrates that animal feeding behavior can reshape microplastic environmental fate and ecological risks, with viruses playing a key mediating role.