Impact of consumer-resource dynamics on C. elegans-E. coli system exposed to nano zero-valent iron (nZVI)

Nano zero-valent iron (nZVI) is one of the most paramount nanoparticles (NPs) applied in environmental remediation, leading to great concerns for the potential impacts on soil ecosystem health. The objective of this study was to link toxicokinetics and consumer-resource dynamics in the Caenorhabditis elegans-Escherichia coli (worm-bacteria) ecosystem. The biokinetic parameters of bacteria and worms were obtained from toxicokinetic experiments and related published literature. Biomass dynamics of bacteria and worms were estimated by employing the modified Lotka-Volterra model. Dynamics of bacteria and worm biomass, internal concentrations of nZVI, bioconcentration factors (BCFs), and biomagnification factors (BMFs) were simulated based on the consumer-resource dynamics. Results showed that the biomass of worms steadily increased from 22.25 to 291.49 g L^-1, whereas the biomass of bacteria decreased from 17.17 to 4.70 × 10^-8 g L^-1 after 96-h exposures of nZVI. We also observed ratios of nZVI concentrations in worms and bacteria increased from 0.06 to 26.60 after 96 h. Moreover, decrements of the bioconcentration factor of E. coli (BCF_E) values from 0.82 to 0.03 after 96 h were observed, whereas values of BMFs increased from 0.06 to 57.62 after 96 h. Internal concentrations of nZVI in worms were found to be mainly influenced by the ingestion rate of bacteria by worms, and the biomass conversion of bacteria had the lowest effect. Implementation of the integrated bioaccumulation-consumer-resource model supports the hypothesis that the C. elegans-E. coli dynamics of internal nZVI concentrations could be effectively associated with the predator-prey behavior and was dominated by the same physiological parameter in the two biological systems.