Arsenic is a noted dangerous metalloid found in many organisms, including humans, that accumulate via food consumption of aquatic products such as macroalgae, particularly where they are a major component of the human diet. The mechanism of accumulation of inorganic arsenic (iAs) as the most toxic form of arsenic (As) was investigated under three different light intensities (LI) (30, 55, and 80 μmol photons m-2 s-1) at varied arsenite (As (III)) concentrations (conc) (0, 125, 250, and 500 μg L-1) using Sarcodia suiae, a red marine macroalga. The depigmentation of the algal fronds from deep red to slightly pinkish-orange and solid green has been confirmed as a form of developmental acclimation, and the direct toxic effects of conc and LI were manifested by the degree of severity of this symptom. Two-way ANOVA showed a significant difference in iAs accumulation which depended upon conc and LI. Stepwise regression analysis showed LI as the second most important variable after conc in all treatments. S. suiae did not appear to intracellularly transform As (III) to arsenate (As (V)); hence, As (III) oxidation seemed to be a preliminary biotransformation as reflected by the dominance and increased accumulation of toxic As (III) by the alga. These findings may render it a prospective environmentally friendly candidate for reducing toxic As hazard risk and as a biological component in the treatment of wastewater. Moreover, these results also suggest that a more concerted effort is required in developing protocols for public health concerns regarding food safety and quality regulations in seafood and products sourced from macroalgae including S. suiae.
Keywords: Arsenite; Inorganic arsenic; Light intensity; Morphology; Sarcodia suiae.