Arsenic detoxification mechanism in marine eukaryotic microalgae Ostreococcus tauri

Marine phytoplankton is able to accumulate arsenic (As), but the resistant mechanisms are unclear. Microalga Ostreococcus tauri (O.tauri), a model organism of natural marine phytoplankton assemblage, was chosen to investigate its As detoxification mechanism. O.tauri was cultivated in pure culture with different concentrations of arsenite (As(III)). The results showed that As(III) oxidation was the main As resistant mechanism. When the microalga was exposed to 30 μmol·L^-1 and 1.67 μmol·L^-1 As(III), more than 90% was oxidized to arsenate (As(V)) after incubation for 60 and 72 hours respectively. After exposed to 30 μmol·L^-1 As(III) for 6 days, dimethylarsenate (DMAs(V)) was detected both in culture medium and algal cells. The study of As biovolatilization by O. tauri showed that this marine microalga was able to biovolatilize As into atmosphere for As detoxification. After exposed to 20, 40, 80 μmol·L^-1 As(III) for 4 weeks, 16.7 ng, 4.0 ng and 1.3 ng volatile As was detected respectively. The results indicated that the As detoxification mechanisms of O. tauri were a combination of As oxidation, methylation and biovolatilization. This study expanded the understanding of As resistant mechanisms of marine phytoplankton and implied that marine organisms might play an important role in As biogeochemical cycle.