Uptake of cadmium by the seagrass Heterozostera tasmanica from Corio Bay and Western Port, Victoria

Abstract

Uptake of cadmium by leaves and root-rhizomes of the seagrass H. tasmanica was studied in laboratory and field experiments. In laboratory experiments, cadmium concentration in leaves approached constant levels after exposure for 192 h to dissolved cadmium at concentrations of 40 and 400µg I^-1. Root-rhizomes, separated from leaves in a partitioned container: did not attain constant cadmium levels under similar conditions. Translocation of cadmium between the leaf and the root-rhizomes was not observed. In field experiments, H. tasmanica containing cadmium at concentrations of 1.8 and 0.4 µg g^-1 in the leaves and root-rhizomes, respectively, and growing in sediment that did not contain measurable cadmium, concentrated that element principally in the leaves when transferred to seawater containing cadmium at concentrations of up to 1.8 µg I^-1. Leaves and root-rhizomes initially containing cadmium at concentrations of 15 and 14 µg g^-1, respectively, lost cadmium when transferred to seawater containing cadmium at less than 0.2 µg I^-1. Approximately 70% of the cadmium accumulated by leaves of H. tasmanica was associated with solid cellular material, 20% with cell fluids and the remainder was sorbed on the leaf surfaces.