Assessment of Water Quality in Darwin Harbour Using Time Integrated Samplers and Biological Markers in Barramundi (Lates Calcifer)

Abstract

A joint collaboration was undertaken to complement the existing Water Quality Monitoring Program in Darwin Harbour. The aim was to assess in situ environmental contaminants and their bioavailability at various sites around Darwin Harbour. Time integrated samplers known as semi-permeable membrane devices (SPMDs) for dissolved polycyclic aromatic hydrocarbons and diffusive gradients in thin films (DGTs) for labile dissolved metal species were deployed in four locations (Sadgroves Creek, Shell Island, Hudson Creek and West Arm) for a period of 10 days. In addition, at Sadgroves Creek and West Arm, biological monitoring was conducted using caged and wild caught barramundi (Lates calcifer). Several biomarkers, already established in barramundi, were evaluated and they included bile metabolites, cytochrome P450s and 7-ethoxyresorufin-O-deethylase (EROD) glutathione S-transferase (GSTs) and cholinesterase activity (ChE). Two other biomarkers were evaluated: vitellogenin in blood to assess potential impact from sewerage into Darwin Harbour, and sorbitol dehydrogenase (SDH), a potential biomarker of liver damage. Results highlight PAH concentrations at the West Arm site were below detection whilst PAH concentration at Sadgroves Creek, Hudson Creek and Shell Island were all similar. For labile dissolved metals, Aluminum, Manganese and Nickel were higher at impact sites as compared to the reference site. Mean concentrations of EROD activity, cytochrome P450, SDH activity, GST, ChE and vitellogenin were not significantly difference (p > 0.05) in barramundi from Sadgroves Creek and West Arm and they were comparable to basal levels measured in hatchery-reared barramundi (T = 0) used as a non-exposed reference. These results provided a baseline survey of PAHs and labile dissolved metals at several sites in Darwin Harbour, which compliments the data being generated from the Darwin Harbour Water Quality Monitoring Program. As development of Darwin Harbour progresses, impacts to the harbour can continue to be monitored and assessed in order to protect the environmental values for Darwin Harbour.