Strengthening the evidence: What is the influence of Fly River discharge on the Torres Strait?

Jane Waterhouse

Mining began in the headwaters of the Fly River in 1984, resulting in significant impacts on the river system including contamination by copper, increased turbidity and modified geomorphology. It is estimated that mining operations have increased sediment discharge of the Fly River by 40%; the close proximity of the Torres Strait to the Fly River mouth has raised concerns that trans-boundary pollution may occur. The extent of this influence was our research focus. We confirmed that habitats located in the northeast of the Torres Strait including Bramble Cay, north of Masig Island, the northern Warrior Reefs and as far northwest as Saibai Island, are located in an area of higher exposure to brackish and turbid waters from the Fly River and local PNG river discharges. Water and sediment quality were generally very good across the region, however, increased metal concentrations in waters and sediments were observed in the same areas of the northern Torres Strait. The trace metal concentrations were relatively low, and hence the extent of environmental risk is currently not of concern. The research highlights the important role of the 1993 Torres Strait Baseline Study in setting an environmental baseline for comparison. It highlights a multiple lines of evidence approach to exposure assessment in remote, complex and data poor marine environments such as the Torres Strait is essential.