Moderate mortality of groundwater copepods Diacyclops humphreysi after exposure to perfluorooctane sulfonate (PFOS).

This study investigates the ecotoxicological impact of perfluorooctane sulfonate (PFOS) on groundwater copepods, which are critical components of aquatic ecosystems. PFOS is recognized as a persistent, bioaccumulative, and toxic organic pollutant, yet its effects on copepods and other stygofauna inhabiting groundwater remain largely unexplored. In this study, we assessed the toxicity of PFOS on the copepod Diacyclops humphreysi using standardized protocols outlined in the literature. Copepods were collected from groundwater bores in the Pilbara region of Western Australia and acclimated for two days before being exposed to a range of PFOS concentrations (0-3241 µg/L). Groundwater from the sampling sites was utilised to prepare PFOS solutions, with two replicates for each concentration and 10-20 specimens per replicate. A time-dependent test was conducted to evaluate toxic effects, with copepod mortality recorded until mortality in the control group exceeded 10%. A logistic model was employed to simulate the dose-response relationship, yielding an estimated LC50 of 469.9 ± 117.1 µg/L and LC10 of 142.4 µg/L PFOS at Day 28 for D. humphreysi. This research provides valuable insights into the toxic effects of PFOS on this typical copepod in Western Australia, contributing to the development of groundwater guideline values for the protection of groundwater ecosystems.