Toxic effects of organophosphate flame retardants on marine microalgae Chaetoceros muelleri: Insights from...

The large-scale use of organophosphate flame retardants (OPFRs) has led to their prevalence in the environment. However, their toxicity on marine microalgae has not been adequately investigated. In this study, we investigated the toxic effects of three representative OPFRs including 2-ethylhexyl diphenyl phosphate (EHDPP), tricresyl phosphate (TCP), and triphenyl phosphate (TPhP) on marine microalgae Chaetoceros muelleri, and explored the potential toxicity mechanisms through transcriptomic analysis. The results demonstrated that OPFRs induced cellular deformation and inhibited the growth of algal cells, with inhibition rates reaching 63.2%, 52.4%, and 72.5% after 96 h at 0.5 mg/L for EHDPP and TCP, and 3.0 mg/L for TPhP. In addition, OPFRs significantly damaged the structure and function of ribosomes in the cells and inhibited the expression of genes for photosynthetic protein synthesis, which in turn suppressed the synthesis of chlorophyll, reduced the ability of light energy conversion, hindered the photosynthetic electron transfer, and triggered the formation of a large number of ROS in the algal cells, leading to lipid peroxidation of the algal cell membranes. These findings provide new insights into the mechanisms of toxicity of OPFRs in marine microalgae and contribute to a better understanding of the ecological consequences of OPFRs in aquatic environments.