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. © 2014 Informa UK, Ltd.