Effect of Organic Matter on the Trophic Transfer of Silver Nanoparticles in an Aquatic Food Chain

The behavior and toxicity of nanoparticles (NPs) could be affected significantly by the ubiquitous natural organic matter (NOM) in aquatic environments. However, the influence of NOM on NPs 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 three typical NOM on the bioaccumulation, trophic transfer and toxicity of 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 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 kinds of NOM could significantly increase the TTF value of Ag NPs ranged from 1.34 to 2.87, which may be ascribed to NOM reducing the capacity for T. thermophila to excrete 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 further understand the interactions between NPs and NOM in various ecosystems