Disparities in Per‐ and Poly Fluoroalkyl Substances (PFAS) Tolerance and Life History Traits in <i>Simocephalus serrulatus</i> Populations

ABSTRACT Per‐ and poly fluoroalkyl substances (PFAS) are nearly ubiquitous contaminants in aquatic ecosystems, causing a litany of toxic effects. Moving forward, understanding the impact of toxic stress and its resulting evolutionary pressures will be crucial to determine how PFAS are altering ecosystems. We assessed the effects of three common PFAS, perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexanesulfonic acid (PFHxS), on two populations of the daphnid Simocephalus serrulatus with different exposure histories. We found that sensitivity to PFOS and PFHxS differed in the two populations. In addition, we found base‐line differences between the populations in development, body size, and reproduction. In particular, the population from the site with a legacy of PFAS exposure showed greater mortality during our chronic experiment. In addition to being the first study to report PFAS toxicity data for this cosmopolitan zooplankton species, these findings show the possible fitness costs associated with populations exposed to PFAS. These findings also highlight the need for considering species, and population‐level differences in tolerance when evaluating the effects of PFAS on ecosystems.