Abstract
This study assessed the bioavailability, toxicity, and transfer of silver nanoparticles (AgNPs) in comparison with AgNO3 in two model food chain organisms: the alga Chlamydomonas reinhardtii and the grazing crustacean Daphnia magna. The effects of phosphate, a potential Ag+-binding ligand and a determinant of phytoplankton productivity, were evaluated. Nano Ag derived from coated AgNPs and AgNO3 was accumulated at similar concentrations into microalgae during high phosphate treatment, but AgNO3 accumulation was increased by low phosphate availability. After feeding on Ag-containing algae, D. magna equally accumulated AgNO3 and nano-derived Ag. There were significant reductions in feeding when D. magna were fed Ag-contaminated algae, with the AgNO3, low phosphate-exposed cells being ingested the least. Nutritional quality characteristics including fatty acid and trace nutrient content were similar in all algal samples, indicating that feeding reduction is specifically due to the presence of Ag, with AgNO3 being more toxic than nano Ag.
Acknowledgments
We thank Paul Lythgoe (Manchester Analytical Geochemistry Unit, School of Earth, Atmospheric and Environmental Sciences, University of Manchester) for the ICP-MS analysis; Samantha Forbes (Electron Microscope Facility, Faculty of Life Sciences, University of Manchester) for assistance with TEM; Dr. Tom Jowitt (Biomolecular Analysis Facility, Faculty of Life Sciences, University of Manchester) for assistance with the DLS analysis; Robert Clay for performing initial characterization of the AgNPs; Dr. Adam Moolna for performing initial algae AgNP exposure experiments; and Dr. Rachel Webster for discussions on the project. This work was supported in part by a grant from the Leverhulme Trust (grant no. F/00 120/BG) to J.K.P.