Chemical- and species-specific toxicity of nonylphenol and octylphenol to microalgae Chlorella pyrenoidosa and Scenedesmus obliquus

Abstract As typical endocrine disrupters, nonylphenol (NP) and octylphenol (OP) are emerging pollutants that have attracted wide attention. This study investigated the toxicity effects of NP and OP on microalgae Chlorella pyrenoidosa and Scenedesmus obliquus, particularly on their growth inhibition, photosynthetic pigment, chlorophyll fluorescence, and superoxide dismutase and malondialdehyde levels. Results showed that the 96 h EC50 of NP and OP was 2.89 and 5.21 mg/L on C. pyrenoidosa, respectively, and 1.54 and 8.48 mg/L on S. obliquus, respectively. NP exerted a stronger inhibitory effect on cell growth, photosynthesis, and PSII activity, and it contributed more oxidative stress on C. pyrenoidosa than on S. obliquus. By contrast, OP exerted a stronger inhibitory effect on S. obliquus than on C. pyrenoidosa. Furthermore, the toxicity of OP to the tested microalgae was lower than that of NP. Principal component analysis (PCA) and Pearson’s correlation indicate that the accumulation of reactive oxygen species is the dominant mechanism of NP and OP cellular toxicity. The principal components of NP and OP affecting microalgae are distinct in the PCA plot, and different endocrine disrupters have varying chemical-specific influences on algal cells. This study confirmed that the toxicity of NP and OP to microalgae C. pyrenoidosa and S. obliquus is chemical- and species-specific. These findings should be considered when assessing the health risk of environmental pollution.