Toxic effect of serial perfluorosulfonic and perfluorocarboxylic acids on the membrane system of a freshwater alga measured by flow cytometry

Flow cytometric measurements were used to investigate the toxic effect of perfluorobutanoic sulfonate (PFBS), perfluorooctane sulfonate (PFOS), perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorododecanoic acid (PFDoA), and perfluorotetradecanoic acid (PFTeA) on some membrane systems of the freshwater alga species Scenedesmus obliquus. Among the test compounds, PFOS, PFDoA, and PFTeA inhibited algal growth rate in a concentration-dependent manner while PFBS, PFHxA, and PFOA did not inhibit algal growth within the test concentration ranges. An enhancement of the mitochondrial membrane potential (MMP) and cell membrane permeability in S. obliquus was observed caused by exposure to PFOS, PFOA, PFDoA, and PFTeA. Both carbon chain length and acid group influenced the toxicity of PFAAs, where the toxicity increased with increasing carbon chain length for the compounds belonging to the same class. The observed effective concentrations lie in the micromole range and the test compounds disrupted membrane properties at concentrations below those associated with algal growth inhibition. Flow cytometry is proved to be a useful technique for toxicity testing with microalgae and provide additional information regarding the mode of action of PFAAs to algal species.