Gold nanoparticle accumulation in amphibian larvae under direct and plant-mediated exposure scenarios

Gold nanoparticles (AuNPs) are increasingly used in industrial and biomedical applications, raising concerns about their release into aquatic environments and their potential effects on non-target organisms. This study evaluated Au uptake by larvae of Rhinella arenarum and the aquatic macrophyte Lemna minor under different exposure scenarios in order to assess the influence of aquatic vegetation on nanoparticle transfer. Three 96-h bioassays were performed: (i) individual exposure of larvae and plants to AuNPs (1 and 10 mg L^- 1), (ii) simultaneous exposure of larvae and plants, and (iii) exposure of larvae to previously contaminated plants in clean medium. Gold concentrations were quantified in both organisms, and accumulation factors (AF) were calculated. Simultaneous exposure resulted in markedly higher Au accumulation in larvae compared with individual exposure, with AF values reaching 6666 ± 1020 L kg^- 1 and 10,089 ± 760 L kg^- 1 at 1 and 10 mg L^- 1, respectively, suggesting enhanced nanoparticle availability under combined exposure conditions. Larvae exposed only through ingestion of previously contaminated plants also accumulated Au, although at lower levels, indicating that trophic transfer contributes to nanoparticle accumulation but less efficiently than direct aqueous exposure. Plants accumulated Au under both isolated and simultaneous exposure conditions, confirming their role as nanoparticle reservoirs in aquatic systems. These findings demonstrate that aquatic vegetation can significantly modulate nanoparticle transfer and availability in freshwater amphibians.