Arsenic and selected elements in marine angiosperms, south-east coast, NSW, Australia

Abstract

The leaves of four angiosperm species, the mangrove Avicennia marina, the samphire Sarcocornia quinqueflora, the seablight Suaeda australis and the seagrass Posidonia australis, were sampled from three locations from the south-east coast of NSW. Mean total arsenic concentrations (mean ± SD) in dry mass for all locations were A. marina (0.38 ± 0.18 to 1.2 ± 0.7 μg g-1), S. quinqueflora (0.13 ± 0.06 to 0.46 ± 0.22 μg g-1), S. australis (0.03 ± 0.06 to 0.05 ± 0.03 μg g-1) and P. australis (0.34 ± 0.10 to 0.65 ± 0.26 ng g-1). Arsenic concentrations were significantly different between species and locations but were consistently low compared with marine macroalgae species. Significant relationships were found between arsenic and iron concentrations for A. marina, S. quinqueflora and P. australis and a negative relationship between arsenic and zinc concentrations for S. quinqueflora. No relationship between arsenic and phosphorus concentrations was found in this study. Angiosperms contained predominantly inorganic arsenic in the water-extractable and residue fractions with minor concentrations of DMA in the water-soluble fraction. P. australis also contained dimethylated glycerol and phosphate arsenoriboses. The presence of arsenobetaine, arsenocholine, trimethylated glycerol arsonioribose and an unknown cation in P. australis is most likely due to the presence of epiphytes on fronds. There is no evidence to suggest that angiosperms produce arsenobetaine as arsenic is mostly present as inorganic arsenic. In conclusion, marine angiosperms only accumulate low arsenic concentrations and uptake appears to be dependent on iron uptake but not phosphorus uptake. Marine angiosperms mainly cycle inorganic arsenic with little biomethylation of arsenic occurring. Copyright © 2007 John Wiley & Sons, Ltd.