Environmental context. Organisms, like commercially available rock oysters, can be used to measure the uptake of contaminants (e.g. trace metals) and thereby provide a relative measure of water quality between sites or of water quality changes over time. However, these measurements cannot be directly compared with water quality guidelines, which require water concentrations and not tissue concentrations, to provide an absolute indication of water quality. The present study found that the amount of copper accumulated in oyster tissue was proportional to water copper concentrations measured by passive sampler devices, thereby allowing oyster copper accumulation to be interpreted in terms of biologically-available copper water concentrations and to be compared with the water quality guidelines.

Abstract. Copper bioaccumulation in transplanted oysters, Saccostrea glomerata, was compared with measurements of water concentrations. Tissue copper measurements were positively correlated with acid-soluble copper concentrations (n = 6, r = 0.874, P = 0.023) and with DGT (diffusive gradients in a thin film)-accumulated copper mass at two sites (n = 9, r = 0.967, P < 0.001; n = 9, r = 0.888, P = 0.001) where continual bioaccumulation occurred. The more significant correlations are likely due to the time-integrated nature of DGT measurements, despite the biomonitor measuring different copper species. This empirical relationship allowed S. glomerata-available copper concentrations (0.70–1.6 μg L^–1) to be modelled across 14 sites and produced a highly significant correlation (r = 0.787, P = 0.001) with DGT-labile copper measurements (0.10–0.49 μg L^–1). This approach allowed biomonitor measurements to be compared with water quality guidelines and would further expand the use of biomonitors for aquatic monitoring if widely replicated.