Short-term exposure to nominal PFBS concentrations is associated with reduced isotopic food uptake in benthic foraminifera

Abstract Pollution caused by per- and polyfluoroalkyl substances (PFAS) is an urgent environmental issue, yet their effects on microbial eukaryotes remain poorly understood. We investigated the association between short-term exposure to nominal concentrations of perfluorobutane sulfonic acid (PFBS), a short-chain PFAS, and isotopic food uptake by five benthic foraminiferal taxa: Bulimina marginata , Cassidulina laevigata , Eubuliminella sp., Globobulimina turgida and Nonionella sp. T1. Foraminifera were exposed for three days and supplied with ¹³C- and ¹⁵N-labelled lyophilized diatoms. Only B. marginata was exposed to the full nominal concentration gradient (0, 0.1, 1, 10 and 100 µg L⁻¹); the remaining taxa were tested at 0 and 100 µg L⁻¹. Across taxa, nominal PFBS treatment was associated with lower pC and pN uptake, while species × treatment interactions were not significant. In B. marginata , both pC and pN uptake differed among concentrations and were significantly lower than the control at 1, 10 and 100 µg L⁻¹ after Tukey adjustment, but not at 0.1 µg L⁻¹. The response was non-monotonic, with partial recovery at 100 µg L⁻¹ relative to 1–10 µg L⁻¹. These results provide initial evidence that short-term exposure to PFBS-containing treatments is associated with reduced isotopic food uptake in benthic foraminifera. Because concentrations were not analytically verified, no methanol-free vehicle control was included, and replication was limited, these results should be interpreted as an acute laboratory hazard-screening study rather than evidence for a biological threshold or species-specific sensitivity.