Arsenic concentrations and speciation in a temperate mangrove ecosystem, NSW, Australia

Total arsenic concentrations and species were measured in the sediments, vegetation and tissues of marine animals from a temperate mangrove ecosystem. Mean arsenic concentrations ranged from 0.3 to 55 μg g -1 dry mass. Epiphytic algae/fungi associated with mangrove fine roots had relatively higher arsenic concentrations (12 ± 3 μg g -1 ) than mangrove leaves, bark or main roots (0.3-1.2 μg g -1 ) and algae/fungi attached to main roots (1.5 ± 0.8 μg g -1 ). The concentrations of arsenic in detritivores (8.5-55 μg g -1 ) were significantly higher than in the major primary producers (0.3-1.5 μg g -1 ), two herbivores (8 ± 1 and 14 ± 2 μg g -1 ) and omnivores (2-16.6 μg g -1 ). Most marine animal tissues contained large percentages of arsenobetaine (28-81%). Glycerol arsenoribose was found in all tissues examined (1-23%) except oyster tissues. Relatively large concentrations of this arsenoriboside were found in the digestive tissues of two crab species (13-23%). Small amounts of trimethylarsoniopropionate (1-8%), tetramethylarsonium ion (1-7%), sulfate arsenoribose (2-13%) and trace amounts of arsenocholine (<1%), trimethylarsine oxide (<1%), dimethylarsinic acid (<2%), phosphate arsenoribose (<2%), arsenate (<1%), and sulfonate arsenoribose (<3%) were found in some tissues. Methylarsonic acid was not found in any tissues. Two unknown cationic arsenic compounds (1-2%) and three anionic arsenic compounds (1-17%) were present in some marine animal tissues. The arsenic concentrations and species found in animals could not be attributed to their position in the food web or feeding mode, but are likely to be related to their dietary intake of arsenic and their ability to assimilate, metabolize and retain arsenic species.