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Full report

• SSR112 - Toxicity assessment of waters from Macquarie Harbour, Western Tasmania, using algae, invertebrates and fish (PDF 4.9 MB)

Separate sections

• Chapters 1-3 (PDF - 2.2 MB)
• Chapters 4-6 and References (PDF - 1.1 MB)
• References and Appendices (PDF - 1.3 MB)

Executive summary

The 100-year operation of the Mount Lyell Mining and Railway Company Limited's copper mine in Queenstown, Tasmania, has resulted in the deposition of over 100 million cubic metres of mine tailings, smelter slag and topsoil into the King River and Macquarie Harbour. Following cessation of tailings discharge into the rivers in December 1994, the Commonwealth and Tasmanian governments are undertaking the Mount Lyell Remediation, Research and Demonstration Program to assess the environmental impact of metal release from the mine and smelter, as part of the development of a remediation strategy. In particular, an assessment of the potential biological impact of elevated copper levels in Macquarie Harbour waters is required.

The objective of this project was to conduct toxicity tests to determine the concentration of copper which can be tolerated in Macquarie Harbour waters without causing detriment to aquatic life. Sensitive sub-lethal tests including phytoplankton growth and enzyme inhibition, amphipod growth inhibition and osmoregulatory and histopathological responses of juvenile flounder were used to determine the toxicity of mid-salinity Macquarie Harbour waters. In addition, a preliminary risk assessment of the potential for toxic effects from copper in Macquarie Harbour is provided, based on values of toxicity in marine and estuarine waters reported in the literature.

Total dissolved copper in Macquarie Harbour waters collected in October and December 1995 for use in the bioassays, ranged from 10 to 42 µg Cu/L, with the highest concentrations immediately below the outflow of the King River. Dissolved copper concentrations exceeded the complexing capacity of the dissolved organic matter in all samples. Electrochemical methods showed that significant amounts of dissolved copper in the Macquarie Harbour waters were present in labile forms (6-24 µg Cu/L) and potentially bioavailable.

Although chemical measurements of copper in the Macquarie Harbour waters, together with the preliminary risk assessment suggested that copper was potentially bioavailable, toxicity testing of mid-salinity Macquarie Harbour waters revealed that there were no significant effects on algal growth, amphipod and juvenile flounder survival, or osmoregulation and copper accumulation in flounder. Of these endpoints, only algal growth inhibition and copper accumulation in flounder were sensitive enough to detect potential effects at copper concentrations found in Macquarie Harbour.

The growth inhibition bioassay with the marine alga Nitzschia closterium was particularly sensitive to copper, with ionic copper concentrations as low as 5 µg/L causing a significant reduction in algal cell division rate over 72 h. However, in general, no toxicity of filtered or unfiltered Macquarie Harbour waters was observed, suggesting that copper in these waters was not present in bioavailable forms. There was, however, significant bioavailable copper to cause inhibition of enzyme activity (β-D-galactosidase) in the marine alga Dunaliella tertiolecta and this bioavailable copper was weakly correlated with labile copper in the Macquarie Harbour waters measured using anodic stripping voltammetry. It is possible that colloidal iron, manganese and aluminium oxides/hydroxides bind copper at the algal cell surface, preventing its uptake into the cell. Enzyme inhibition may occur at the cell membrane, whereas growth is not affected because copper adsorbed to metal hydroxides cannot penetrate the cell membrane.

Amphipod growth was a sensitive indicator of copper toxicity, with ionic copper concentrations as low as 4 µg Cu/L causing a significant decrease in growth over 28 days. A small but significant decrease in amphipod growth in station 14 water was observed, with no effect in station 9 water.

Although increases in copper content of flounder exposed to low concentrations of ionic copper were found, copper content of fish exposed to Macquarie Harbour waters for 14 days was the same as the controls. This supports the algal growth bioassays which suggested that much of the copper present in the Harbour was not bioavailable.

Ionic copper and Macquarie Harbour waters caused histopathological changes in juvenile flounder after 14-day exposures, including effects on the gills (epithelial necrosis, epithelial lifting and proliferation of chloride cells), liver (cloudy swelling) and kidneys (necrosis). However, apart from cloudy swelling in the liver, these effects were only observed at concentrations of ionic copper greater than that found in the Macquarie Harbour samples(>40 µg/L). It appears therefore that copper in the Macquarie Harbour waters was not the sole cause of these histopathological changes. Other metals or compounds in the Harbour waters may contribute to these effects.

Taking into account these results, and using the results of the risk analysis of literature values of copper toxicity in marine and estuarine waters, we estimate the maximum acceptable concentration of copper in Macquarie Harbour mid-depth waters to lie between 10 and 20 µg/L. This will require at least a four-fold reduction of dissolved copper from present levels.