Metal bioavailability to the soldier crab Mictyris longicarpus

Abstract

The bioavailability of copper, zinc, lead, cadmium, manganese and iron to a marine invertebrate, the soldier crab, Mictyris longicarpus, has been examined in the laboratory using both metal-spiked sediments and contaminated sediments from field sites. Background concentrations of copper, zinc, lead, cadmium and manganese in field crabs did not vary greatly in a range of different body sizes and all accumulated zinc, lead, cadmium, manganese and iron. Copper was only accumulated from sediment spiked with a high concentration of copper, which also had toxic effects. Accumulated metals were mostly derived from sediment rather than the water column. The sediment particles ingested by the crabs were also analysed. Correlations between lead and cadmium in these particles in the crabs were significant. Metals accumulated in the crabs and two chemical extractions of sediment were also compared. The correlations between lead and cadmium extracted by EDTA and that in the crabs were significant. HCl extraction of sediment could reflect the bioavailability of lead to the crabs but not the bioavailability of cadmium. The correlations between metal in crab and extractable metal in sediment were improved for manganese and cadmium by normalizing to iron concentrations. The crabs were able to regulate their body concentrations of zinc to about 100 μg/g when exposed to all but the most contaminated field sediment. Accumulated zinc was depurated after the crabs were transferred to an uncontaminated environment, whereas accumulated lead was not.