Hypersalinity and environmentally relevant perfluorohexanesulfonic acid independently and interactively impair survival and development in early life stage red drum (Sciaenops ocellatus)

Estuaries serve as critical nursery habitat for many economically and ecologically important marine species, yet they are increasingly subject to salinity extremes driven by drought, reduced freshwater inflow, and coastal urbanization, as well as to contamination by per- and polyfluoroalkyl substances (PFAS) originating in developed watersheds. Despite this convergence of stressors, the effects of PFAS on estuarine fishes remain understudied, particularly in combination with the natural fluctuations that characterize these systems. The present study investigated the interactive effects of osmotic stress and an environmentally informed concentration of an understudied replacement PFAS, perfluorohexanesulfonic acid (PFHxS), on early life stage (ELS) red drum ( Sciaenops ocellatus ). Embryos from four independent spawns were exposed to 0 or 1 µg/L PFHxS at four salinities (30, 35, 39 and 43 ppt) in a fully crossed factorial design, using dish as the experimental unit (96 dishes; 1, 920 embryos). PFHxS reduced the odds of hatching by approximately 60%, which carried through to an approximately 36% reduction in the odds of cumulative survival to 48 h that was most pronounced at intermediate salinities. PFHxS did not affect post-hatch survival of larvae that successfully hatched, whereas hypersalinity independently reduced both hatching and post-hatch survival. Among surviving larvae, PFHxS reduced relative yolk sac area and relative brain area and increased the odds of unpigmented eyes approximately five-fold. Results reported herein demonstrate that an environmentally informed concentration of PFHxS is sufficient to adversely affect both the survival and the development of an estuarine-dependent sportfish and address several important data gaps pertaining to the biological risks of replacement PFAS, including multi-stressor interactions and effects on the early development of a large-bodied marine species.