Molluscan biomonitor for quantification and impact assessment of estrogenic and metallic contaminants in Australian marine ecosystems

Abstract

Research Doctorate - Doctor of Philosophy (PhD)Estrogenic compounds have been identified as a potential cause of reproductive effects in aquatic wildlife worldwide. This thesis was focused on the development of a native Australian species, the Sydney rock oyster Saccostrea glomerata, as a biomonitor of estrogenic compounds in Australian marine ecosystems. Biomarkers of estrogenic exposure in S. glomerata were examined under laboratory and field exposures to estrogenic compound/s. Laboratory exposure of 17α- ethynylestradiol (EE2) to S. glomerata elevated vitellogenin (precursor to the female egg yolk protein) production in both females and males in a dose dependent manner but vitellogenin concentrations declined to basal levels after 49 days exposure. Exposure to EE2 was also capable of inducing accelerated female development, enlarged oocytes and an increase in the proportion of females. Increased proportions of females together with histological observations suggested that a complete sex reversal had occurred from male-intersex-female for a proportion of individuals. A novel real-time qPCR assay for S. glomerata vitellogenin was developed. Sequencing of partial fragments of vitellogenin mRNA and vitellogenin genomic DNA allowed the identification of an intron-exon boundary and the development of real-time qPCR primers. Real-time qPCR revealed that female vitellogenin gene expression responded in a dose response fashion in individuals exposed to a concentration gradient of EE2 for 4 days. To further test biomarker utility, S. glomerata were deployed in the receiving waters of Burwood wastewater treatment plant (WWTP) for 6 weeks, during which effluent was analysed for estrogenic compounds and activity. Sewage effluent from Burwood was found to contain both estrogenic compounds and activity, also S. glomerata deployed at Burwood had higher female vitellogenin (both protein and gene expression) and a higher proportion of mature females compared to individuals at reference locations. As S. glomerata is an established biomonitor of metallic contaminants, it was employed for the analysis of heavy metals in individuals deployed at Burwood and reference locations. Concentrations of heavy metals in S. glomerata were found to be at low concentrations and within boundaries of spatial variation. Overall, findings indicate that S. glomerata would be suitable as a biomonitor of estrogenic exposure and effects in the marine environment