Effect of organic matter on the trophic transfer of silver nanoparticles in an aquatic food chain

The behavior and toxicity of nanoparticles could be affected significantly by the ubiquitous natural organic matter (NOM) in aquatic environments. However, the influence of NOM on nanoparticles along the food chain remains largely unknown. This study constructed bacteria Escherichia coli (E. coli) – protozoa Tetrahymena thermophila (T. thermophila) to evaluate the influence of NOM on the bioaccumulation, trophic transfer and toxicity of silver nanoparticles (Ag NPs). Results demonstrated that NOM could reduce the toxicity of Ag NPs to E. coli and T. thermophila by different influence mechanisms (e.g., reduce Ag NPs accumulation or complex with dissolved silver ion (Ag⁺)) which related to the type of NOM and organisms. Moreover, Ag NPs can be transferred and biomagnified to T. thermophila via trophic transfer. Three typical NOM could significantly increase the trophic transfer factors of Ag NPs ranging from 1.16 to 2.49, which may be ascribed to NOM reducing the capacity for T. thermophila to excrete total silver (Ag) as NOM could significantly change the form of Ag. These findings provide a novel insight into the impact of NOM on the ecological risk posed by Ag NPs through the food chain and emphasize the need to understand further the interactions between nanoparticles and NOM in various ecosystems.