In the aquatic environment natural concentrations of zinc in the water column are vital to supporting biota. However, due to anthropogenic activities such as mining and broader industrialisation, concentrations of zinc in waterways have increased globally to concentrations well above those needed to sustain life.
Currently, Australia and New Zealand have guideline values for zinc which can be adjusted to consider the regional water hardness. However, the toxicity and bioavailability of zinc is not only influenced by water hardness, but also by other water quality parameters such as pH and the concentration of dissolved organic carbon (DOC). Globally, there has been a greater emphasis on considering these toxicity modifying factors (TMF), particularly for deriving site-specific guideline values for metals. Bioavailability models such as multiple linear regression (MLR) models and the biotic ligand model (BLM) are increasingly being used in Canada, USA and Europe to derive metal bioavailability-based criteria.
We collected natural waters with varying water chemistries from multiple geographically and biogeochemically-diverse sites across Australia. Chronic toxicity bioassays with the Sydney strain of the cladoceran Ceriodaphnia dubia were carried out and the effect concentrations (EC) that caused a 10% and 50% decrease in reproduction were experimentally estimated. The effect concentrations will be compared to predicted values from pre-existing bioavailability models. This will determine whether the bioavailability models derived from Northern Hemisphere conditions are applicable for the prediction of zinc toxicity to invertebrates in Australian natural waters.