Trophic transfer of per- and polyfluoroalkyl acids in a periphyton-mayfly-zebrafish food chain

Per-and polyfluoroalkyl substances (PFAS) are ubiquitous contaminants in freshwater ecosystems. Many PFAS are incorporated into food webs, with potential effects on ecological and human health. However, PFAS incorporation into the base of aquatic food webs remains poorly understood. The goal of this study was to quantify the uptake and trophic transfer of both legacy PFAS and the perfluoroether acid Nafion byproduct 2 (NBP2) using a simulated freshwater food chain in a lab setting. Natural periphytic biofilms were placed into trays containing equimolar binary aqueous PFAS mixtures at environmentally relevant concentrations for five days. Following the initial exposure period, newly hatched mayfly larvae were introduced into each tray to feed on periphyton for most of their larval development. The mature larvae were then fed to zebrafish. All water and biota samples contained detectable levels of the tested PFAS. All PFAS were more concentrated in periphyton than in water, and four of six PFAS were further concentrated in mayfly larvae relative to periphyton. PFDA was the most accumulative in all biota. PFAS concentrations in zebrafish were significantly correlated with those in larval mayflies. Assimilation efficiencies in zebrafish were high (>70 %) for all compounds. Bioaccumulation of PFAS in periphyton and mayflies was positively correlated with log K_OW and number of carbons. Our findings demonstrate the functionality of the periphyton-mayfly-zebrafish food chain for studying the trophic transfer of PFAS, and provide novel data showing that the bioaccumulation of NBP2 is comparable to legacy PFAS.