Abstract

Arsenic concentrations were measured in thirteen macroalgal species from Sydney, Australia. Brown macroalgae contained, on average, more arsenic (range, mean ± s.e.: 5–173 μg g^–1, 39 ± 4 μg g^–1) than either green (0.12–30.2 μg g^–1, 10.7 ± 0.7 μg g^–1) or red macroalgae (0.11–16.9 μg g^–1, 4.3 ± 0.3 μg g^–1). Despite the overlap in arsenic concentrations between different macroalgal species, inter-species arsenic variation was apparent with arsenic concentrations following the order brown > green > red macroalgal species. It was concluded that the main contribution to the variation in arsenic concentration was from natural variability expected to occur between individuals of any species as a result of physiological differences.

Most of the arsenic compounds in macroalgae (70–108%) could be extracted using methanol/water mixtures, with 38–95% of the arsenic compounds present in characterizable forms. All macroalgal species contained arsenoribosides (9–99%). The distribution of arsenoribosides followed a general pattern; glycerol-arsenoriboside and phosphate-arsenoriboside were common to all macroalgal species. Sulfonate-arsenoriboside and sulfate-arsenoriboside were found in brown macroalgal species and one red macroalgal species. Six macroalgal species contained high concentrations of inorganic arsenic (14.2–62.9%) and four species contained high concentrations of dimethylarsinic acid (13.3–41.1%). The variation in the distribution of arsenic compounds in marine macroalgal species appears to be related to taxonomic differences in storage and structural polysaccharides.