Arsenic speciation in Asiatic algae: Case studies in Asiatic continent

Arsenic (As) is a toxic metalloid and its contamination in algal products may pose risks to organisms at higher trophic levels and humans. The toxicity, bioaccumulation, and fate of As in algae are largely determined by its speciation, and As speciation changes are greatly driven by biotransformation processes. This chapter reviewed the As bioaccumulation and speciation in microalgae and macroalgae from Asiatic continent and illuminated the As biotransformation processes as well as their genes involved in algae. Both microalgae and macroalgae have high ability to bioaccumulate inorganic As from ambient water and biotransform inorganic As into methylated As and complex organoarsenicals through As redox and methylation/demethylation cycles as well as other organoarsenicals formation, leading to a wide variety of As species existed in various algae. Subtle difference in As bioaccumulation and species distribution exists between microalgae and macroalgae as well as in different algal phyla. Several genes and enzymes involved in As redox and methylation/demethylation reactions have been identified and characterized, while other genes and enzymes participated in As biotransformation remain unknown. Future research should focus on (1) the regulatory mechanism of As bioaccumulation and resistance; (2) identification and characterization of more organoarsenicals and their risk assessment; and (3) molecular mechanism of As biotransformation processes.