The toxicity, bioaccumulation and debromination of BDE-47 and BDE-209 in Chlorella sp. under multiple exposure modes

Polybrominated diphenyl ethers (PBDEs) are a series of important persistent organic pollutants (POPs) in marine environments. Microalgae are the start of PBDEs bioaccumulated and bioconcentrated along the marine food web. In order to investigate the variations of PBDEs bioaccumulation by microalgae and its influencing factors, we set up a series of experiments with Chlorella sp. under different BDE-47 or BDE-209 exposure modes to measure their toxicity, bioaccumulation and degradation patterns. The inhibition effect on cell growth was much more obvious in BDE-47 than BDE-209, with the EC₅₀ values at 96 h calculated as 64.7 μg L^-1 and 4070 μg L^-1, respectively. Microalgal uptake rates showed BDE-209 diffused less into cells than BDE-47, with highest measured uptake rates of 0.145 × 10^-7 μg h^-1 cell^-1 and 0.45 × 10^-7 μg h^-1 cell^-1, respectively. The bioaccumulation amount by unit microalgal cell varied with PBDE concentrations and culture time, which appeared to be related to the changes of extracellular polymeric substances (EPS) and cellular neutral lipids under the toxicity of PBDEs. Finally, we found Chlorella sp. delayed the debromination patterns of BDE-209 compared to seawater. This study linked the toxicity, microalgal bioaccumulation and metabolism of PBDEs, provided new insights in the research of POPs by microalgae and marine food webs.