Heavy metals in Diadema setosum (Echinodermata, Echinoidea) from Singapore coral reefs

Concentrations of Zn, Pb, Cd, Fe, Cr, Cu and Ti were measured in body compartments of the echinoid Diadema setosum and in the silt fraction of surface sediment from eight coral reefs in Singapore coastal waters. Metal concentrations in the echinoid varied with the body compartment analysed and with the site of sampling. Amongst the body compartments studied Zn, Cd, Fe, Cr and Cu were preferentially accumulated in the gonads, whereas Pb and Ti were accumulated mainly in the calcified body compartments. The concentrations of most metals differed according to the reef sampled. A decreasing north-south gradient of metal concentrations was observed in D. setosum populations, correlating to the distance from Singapore. A similar gradient was observed for metal concentrations in sediment. It is suggested that D. setosum could be a valuable bioindicator for assessing heavy metal contamination in coral reef ecosystems of the Indo-West Pacific.