A mouthful of mud: the fate of contaminants from the Fitzroy River, Queensland, Australia and implications for reef water policy

Abstract

It is widely accepted that contaminants in storm runoff and flood waters can cause a decline in the health of coral reef ecosystems. The Fitzroy River catchment in Central Queensland, Australia is thought to contribute substantial amounts of contaminants to the Great Barrier Reef (GBR) lagoon. Just how much of this material actually reach the GBR lagoon is not well understood. To help address this knowledge gap a moderate flood in the Fitzroy River was intensively sampled 60km upstream of the river mouth, and at the river mouth and along the flood plume at near peak discharge. The upstream sampling site proved to be a poor indicator of the actual suspended sediment load delivered to the GBR lagoon. About 90 % of the suspended sediment was being deposited close to the river mouth, in comparison, a high percentage of dissolved nutrients were transported into the GBR lagoon. Reef water quality policy may need to take the sediment trapping efficiency of estuaries into account. These findings will be useful in validating catchment and receiving waters models and for informing target setting mechanisms aimed at meeting reef water quality policy.