Temperature Modulates PFAS Accumulation and Effects on Metabolic Performance in Sheepshead Minnows

Climate warming and chemical pollution shape aquatic ecosystems, yet the physiological mechanisms underlying their combined effects remain unclear. We investigated how projected increases in mean summer surface water temperature alter per- and polyfluoroalkyl substance (PFAS) toxicokinetics and their effects on the physiological performance of sheepshead minnows (<i>Cyprinodon variegatus</i>). Adult fish were chronically exposed to an environmentally relevant PFAS mixture (perfluorooctanesulfonate (PFOS) + perfluorooctanoate (PFOA)) under current and projected mean-temperature scenarios. Tissue PFAS concentrations, whole-organism metabolic rates, swimming performance, reproductive output, and somatic indices were assessed. Temperature modified PFAS tissue concentrations in a compound- and tissue-specific manner, notably promoting PFOA redistribution to eggs. Metabolic responses were temperature-dependent: at 26 °C, higher tissue PFAS concentrations were associated with elevated standard and maximum metabolic rates (SMR and MMR), maintaining aerobic scope (AS). At 28.5 °C, SMR remained stable while MMR and AS declined with rising PFAS, indicating less oxygen for energetically demanding activities. Despite unchanged performance outcomes for swimming and reproduction, increase in hepatosomatic index with increasing tissue PFAS concentrations and altered PFAS distribution suggests detoxification costs. These findings indicate that increases in mean water temperature are likely to exacerbate contaminant stress, with consequences for coastal fish population resilience and offspring development. PFAS risk assessment should consider costressors under projected warming.