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• SSR163 - Copper speciation and toxicity in a contaminated estuary (PDF - 444 KB)

Executive summary

This report describes a brief study of the relationship between chemical and biological estimates of toxicity in a contaminated estuarine waterbody. A suite of tests was conducted using organisms chosen to represent several trophic levels and taxonomic groups. Four species were screened for suitability including the marine alga Nitzschia closterium, the sea urchin Heliocidaris erythrogramma, the rotifer Brachionus plicatilus, and the brine shrimp Artemia salina. The marine alga was found to be the most suitable species for testing, due to the ease of culture, sensitivity to copper, and reliability and repeatability of the tests.

Copper speciation was investigated using Anodic Stripping Voltammetry (ASV-labile copper), free copper by Ion Selective Electrode and total copper to determine if copper toxicity of estuarine samples could be predicted from chemical parameters. Algal tests were used to investigate copper speciation and toxicity in samples collected fom Macquarie Harbour, a contaminated estuary in Tasmania. Nitzschia closterium showed a strong correlation between toxicity and free copper in laboratory studies using clean seawater. No toxicity was observed in the field samples, despite significant levels of 'bioavailable copper' measured by ASV. Potentiometric measurements of copper showed there was insufficient free copper present in the samples to cause toxicity. Free copper measurements, in conjunction with other speciation techniques and bioassay data, can contribute to a better understanding of bioavailability and toxicity to aquatic organisms.