Arsenic concentrations and speciation in the tissues and blood of sea mullet (Mugil cephalus) from Lake Macquarie NSW, Australia

Total arsenic concentrations and species were measured in the tissues and blood of the mullet Mugil cephalus. Arsenic concentrations ranged from 0.54 μg/g dry mass in the gill tissue to 19.2 μg/g dry mass in liver tissue. The concentrations of arsenic in liver tissues were found to be significantly greater (P>0.01) than in other tissues. Significant correlations exist between arsenic concentrations in all tissues. There was no significant difference (P>0.05) in arsenic concentrations between male and female fish. Age was found not to influence arsenic concentration. Significant regressions of arsenic concentration against mass were found for stomach (r2=0.23, P<0.01), gill (r2=0.143, P<0.05), intestine (r2=0.138, P<0.05) and gonad tissues (r2=0.13, P<0.05). Most tissues and blood contained large percentages of arsenobetaine (35%–100%) and with the exception of muscle and gonad tissues, dimethylarsinic acid (7%–62%). Smaller percentages of trimethylarsine oxide (TMAO) (4%–14%) were found in stomach, intestine and kidney tissues; arsenate (1%–6%) in stomach, intestine, liver, gonad tissues and blood and arsenocholine (2%–3%) in all tissues except muscle. Traces of arsenic sugars were found in stomach, intestine, kidney and gonad tissues. The species of arsenic found in tissues and blood can be explained by the ingestion and degradation of organic arsenic compounds found in fauna and flora consumed by mullet. The conversion of inorganic arsenic obtained through ingestion of sediment to organic arsenic compounds by microbial processes in the digestive system and enzymes in the liver may also be occurring.