The influences of dissolved inorganic and organic phosphorus on arsenate toxicity in marine diatom Skeletonema costatum and dinoflagellate Amphidinium carterae

In this study, arsenate (As(V)) uptake, bioaccumulation, subcellular distribution and biotransformation were assessed in the marine diatom Skeletonema costatum and dinoflagellate Amphidinium carterae cultured in dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP). The results of 3-days As(V) exposure showed that As(V) was more toxic in DOP cultures than in DIP counterparts. The higher As accumulation contributed to more severe As(V) toxicity. The 4-h As(V) uptake kinetics followed Michaelis-Menten kinetics. The maximum uptake rates were higher in DOP cultures than those in DIP counterparts. After P addition, the half-saturation constants remained constant in S. costatum (2.42-3.07 mu M) but decreased in A. carterae (from 10.9 to 3.8 mu M) compared with that in the respective P-depleted counterparts. During long-term As(V) exposure, A. carterae accumulated more As than S. costatum. Simultaneously, As(V) was reduced and transformed into organic As species in DIP-cultured S. costatum, which was severely inhibited in their DOP counterparts. Only As (V) reduction occurred in A. carterae. Overall, this study demonstrated species-specific effects of DOP on As(V) toxicity, and thus provide a new insight into the relationship between As contamination and eutrophication on the basis of marine microalgae.

Automated summary

In this study, the uptake, bioaccumulation, subcellular distribution, and biotransformation of arsenate (As(V)) were assessed in two marine microalgae species, Skeletonema costatum and Amphidinium carterae, cultured in dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP). The results showed that As(V) was more toxic in DOP cultures than in DIP cultures, and higher As accumulation contributed to more severe toxicity. The uptake kinetics of As(V) followed Michaelis-Menten kinetics, with higher maximum uptake rates in DOP cultures. Additionally, the study found that DOP affected the half-saturation constants differently in the two species. S. costatum maintained constant constants, while A. carterae showed a decrease after P addition. The long-term exposure also revealed species-specific effects, with A. carterae accumulating more As and undergoing only As(V) reduction, while S. costatum showed As(V) reduction and transformation into organic As species, which was inhibited in DOP cultures. Overall, this study provides new insights into the relationship between As contamination and eutrophication based on marine microalgae.