Contaminant pathways in Port Curtis: Final report - OzCoasts

Contaminant pathways in Port Curtis: Final report7: Antioxidant enzymes as biomarkershomeostasis (Ringwood et al. 1999). Glutathione (GSH) is a low molecular weightscavenger of oxygen radicals which is often found to be depleted in contaminantexposedorganisms (Regoli et al. 1998).The major objective of this study was to determine whether selected biomarkerscan be used as bioindicators of metal-induced stress in oysters, both in the fieldand in the laboratory. The laboratory experiment was used to establish clearcause–effect relationships without any confounding variables often found in thefield environment, and without the presence of unknown mixtures of contaminants.Copper was selected for the laboratory exposures because, in addition to beingidentified as a contaminant of concern in Port Curtis (Andersen & Norton 2001;Andersen et al. 2005a), the metal had been shown to induce strong biomarkerresponses in other studies (Regoli & Principato 1995; Doyotte et al. 1997; Regoliet al. 1998; Brown et al. 2004). Bivalves have also been successfully used inbiomarkers studies, showing significant variation in a range of biochemicalmarkers, in both gill and digestive gland tissues (Cheung et al. 2001; Cheunget al. 2002; Irato et al. 2003).In this study, the Sydney rock oyster (Saccostrea glomerata) was chosen as asuitable biomonitor. Oysters are suspension feeders and take up metals bothdirectly from sea water and from suspended particles collected during feeding(Rainbow 1995). Due to their ability to accumulate contaminants, oysters havebeen successfully used as biomonitors in many pollution assessment studies inPort Curtis (Andersen et al. 2003; Andersen et al. 2004; Andersen et al. 2005b),and elsewhere (Odzak et al. 2001). The use of transplanted oysters has severaladvantages and has been used successfully in several previous studies (Curranet al. 1986; Chan et al. 1999) including those in Port Curtis mentioned previously.7.2 ExperimentalThe field component of the research involved the measurement of biomarkers(CAT, LPO, GSH and GST) and metal concentrations in oysters deployed at twosites; one in the inner harbour area and the other outside of Port Curtis. Bothsites have been monitored previously for other research in Port Curtis. Site 1 isconsidered an impacted site located adjacent to the Fisherman’s Landing tradewaste effluent outfall (Figure 7.1) where metal bioaccumulation has beendemonstrated (Andersen et al. 2005b). Site 2 is relatively pristine, located on theoceanic side of Curtis Island. Previous studies indicate metal bioaccumulation inthis area to be low (Andersen et al. 2005a).81