Physiological Characteristics and Behaviors Determining the Resistance of Freshwater Microalgae to Perfluorooctanoic Acid

Abstract

Perfluorooctanoic acid (PFOA) is a persistent and bioaccumulative pollutant in aquatic environments, posing a significant threat to various organisms, including microalgae. Owing to the differences in research conditions of relevant studies, there is limited knowledge regarding the evaluation of resistance performance and strategies among different freshwater microalgae when exposed to PFOA. In this study, two representative freshwater microalgae, Chlorella sp. and Microcystis aeruginosa, were selected to comprehensively explore their resistance to PFOA exposure. The results showed that Chlorella sp. exhibited superior resistance to PFOA compared to M. aeruginosa, primarily due to its higher photosynthetic efficiency and more rapid mobilization of antioxidant responses. Additionally, Chlorella sp. was capable of extracellularly degrading PFOA at low PFOA concentrations, thereby reducing the actual concentration of PFOA affecting the Chlorella cells. Furthermore, Chlorella sp. cells exhibited self-aggregation, driven by proteins in extracellular polymeric substances (EPSs), which provided protection against PFOA exposure. In contrast, the high polysaccharide content in the EPS secreted by M. aeruginosa led to increased PFOA adsorption and uptake by the cells, resulting in severe physiological effects. This study enhances the understanding of the pivotal roles played by physiological characteristics and behavioral patterns of freshwater microalgae in their resistance to PFOA.