A comparative evaluation of oysters, mussels and sediments as indicators of trace metals in Hong Kong waters

Abstract

Oysters (Saccostrea glornerata = Crassostrea glornerata Gould) taken from 20 locations revealed considerable contamination of the heavily urbanised Victoria Harbour area by copper and zinc. Data for copper and zinc in sediments, based on samples from 210 sites, confirmed this finding. In addition, mussels (Septifer bilocularis [L.]) were collected twice from 23 locations. Copper concentrations in the mussels were in qualitative agreement with the profiles derived from oyster and sediment investigations. However, the relative enrichment of samples from Victoria Harbour and those from elsewhere was less in mussels than in oysters and sediments, suggesting partial regulation of copper by mussels. Zinc was regulated by the nlussels to a much greater extent, differences in zinc concentration between groups of samples or individual samples belng minimal. No parallelisnl existed between oyster, sediment and mussel results with respect to iron levels in the coastal environment of Hong Kong; presumably, the kinetics of iron differ considerably in the 2 bivalve species. We propose that S. bilocularis is unsuitable as an indicator organism of trace metals due to partial or complete metabolic regulation. Future studies in the tropics should be cognizant of this possibility when employing other previously unstudied bivalve species as bio-indicators.