Monitoring of benthic invertebrates in Macquarie Harbour, western Tasmania
Supervising Scientist Report 115
Talman S, O'Connor N, Zampatti B and Cannon F
Supervising Scientist, 1996
ISBN 0 642 24314 X
Over the last century Macquarie Harbour and the Mount Lyell region to the north-east of the Harbour have been affected by mining activities at the Mount Lyell copper mine. In that time the mine has discharged large quantities of mine tailings into the Queen River. This material has been washed downstream, resulting in the deposition of over 100 million cubic metres of tailings, as well as slag and topsoil, in the King River and Macquarie Harbour.
In 1995 the Tasmanian and Federal Governments established a joint program, the Mount Lyell Remediation Research and Demonstration Program (MLRRDP), aimed at investigating remediation strategies for the impacted areas. As part of MLRRDP Project 13B, Water Ecoscience P/L have begun an ongoing biological monitoring program aimed at assessing the ecological health of Macquarie Harbour. In accordance with the first objective of this program, a survey of benthic invertebrates in Macquarie Harbour was conducted in order to establish the current status of this community.
The use of benthic invertebrate communities as a biomonitor in Macquarie Harbour follows recommendations based on a pilot biological survey conducted by Water Ecoscience P/L in 1995 (O'Connor et al 1996). Benthic invertebrate communities were found to fit the selection criteria more closely than other ecosystem components (eg macroalgae, seagrass, zooplankton, phytoplankton and fish).
In addition to recommending the use of benthic invertebrates to detect recovery of ecosystem health, O'Connor et al (1996) outlined the most suitable program design, including statistical analysis, dependent variable selection, site selection and environmental variable selection. This design was adopted for the biological monitoring program.
This report presents the findings of the initial benthic invertebrate survey in Macquarie Harbour for the biological monitoring program.
The results indicate an impoverishment of invertebrate species and individuals in Macquarie Harbour when compared with coastal embayments elsewhere in south-eastern Australia (eg Poore et al 1975, Poore 1982, Edgar 1991). In an estuary the size of Macquarie Harbour, around 100 to 200 species of benthic invertebrates might be expected to occur if the area were free of mining impacts. In the present study 45 species were collected which brings to 84 the total number of benthic invertebrate species recorded from Macquarie Harbour.
Copper contamination and sediment organic matter content appear to be the main determinants of the current population structure, as species richness, total abundance and species distribution all followed a pattern which corresponded to the pattern of sediment copper concentrations and the amount of sediment organic matter in the harbour. Other environmental factors such as sediment grain size, depth and temperature did not appear to affect the abundance and diversity of benthic invertebrates.
The copper concentration of waters entering Macquarie Harbour from the King River is expected to decline with remediation of the Mount Lyell mine site and the Queen and King Rivers. Any change to the benthic invertebrate community of Macquarie Harbour as a result of improving sediment and water quality is likely to be detected in future surveys with the present study providing valuable baseline data.