Total and inorganic arsenic contents in seaweeds: Absorption, accumulation, transformation and toxicity

Arsenic metabolism in macroalgae has gained considerable interest because it controls the risk of arsenic contamination in algal products. This article reviews the total and inorganic arsenic contents in seaweeds, including 92 (red), 154 (brown) and 36 (green) species belonging to Rhodophyta, Phaeophyta and Chlorophyta, respectively. All the data collected from the published seaweeds support the conclusion that the total and inorganic arsenic contents in seaweeds are category-dependent, with species from Phaeophyta having the highest and those from Chlorophyta having the lowest. Total arsenic contents in the top 10 species of Phaeophyta are all over 100 mg kg(-1) DW, but those in the top 7 species of Rhodophyta and the top 3 species of Chlorophyta vary from 20 to 50 mg kg(-1) DW and 10 to 15 mg kg(-1) DW, respectively. The average total and inorganic arsenic contents in species of Phaeophyta are significantly (P < .05) higher than those in species belonging to Rhodophyta and Chlorophyta. Furthermore, Phaeophyta also contain a much higher percentage of inorganic arsenic with respect to total arsenic than either Rhodophyta or Chlorophyta. In addition, this article also reviews the effects of environmental factors on the absorption, bioaccumulation and biotransformation of arsenic species in seaweeds.