Historical heavy metal contamination from local copper mining presents ongoing environmental concerns in Macquarie Harbour, on the west coast of Tasmania. These heavy metals can occur in different phases which reflect how mobile and thus bioavailable they can be and how they move through benthic and, eventually, pelagic biota. A major parameter that can control the mobility of heavy metals is dissolved oxygen (DO). Macquarie Harbour is naturally low in DO due to its bathymetry, with a shallow and narrow opening to the ocean restricting oxygen replenishment to the Harbour from oceanic waters. Compounding these naturally low DO levels, increased organic matter produced by finfish aquaculture in the Harbour drives bacterial communities to utilise more oxygen, depleting DO even further.
Understanding heavy metal mobility in Macquarie Harbour is complex and dynamic, but also essential to informing extensive and ongoing monitoring and management efforts in the Harbour. Using a Unisense benthic lander, heavy metal fluxes can be measured in situ to increase our understanding of legacy heavy metal contamination in the context of changing DO and increased organic matter. This information can discern if the sediments of the Harbour are a source or sink of heavy metals to the overlying water column and what might occur when physicochemical properties are altered either through direct anthropogenic activities (i.e. mining and aquaculture) or indirect long-term shifts (i.e. a changing climate).
This Honours project aims to elucidate heavy metal fluxes with varying levels of organic matter and DO in Macquarie Harbour to act as a baseline, along with a methodological trial of lander incubations. The findings of this project will contribute to the ongoing monitoring and management of this complex and dynamic environment.
This project is funded by the Australian Government through the Fisheries Research and Development Corporation (FRDC) and the Department of Climate Change, Energy, the Environment and Water (DCCEEW) as part of the broader Oxygen Offset Program in Macquarie Harbour (OOPMH).
Honours student: Kira Sirois
