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Abstract
Over the past two decades, biomarker responses have been increasingly used within environmental monitoring programmes to provide information on the adverse effects of contaminants. Evidence for the ecological relevance of biomarkers and large-scale assessments of their applicability as sensitive indicators of contaminant stress in the field are rare. This thesis investigates the use of biomarkers as indicators of biological effects from anthropogenic pollution in marine filter feeding organisms. I focus particularly on the ecological relevance and consistency of biomarker responses over large spatial scales in the presence of multiple stressors, and their potential application for the improved monitoring of current ecological threats; re-suspended contaminated sediments and industrial discharge associated with oil and gas drilling activities.
Using a series of laboratory and field experiments, cellular biomarkers were developed and their utility evaluated in two organisms; the Sydney rock oyster Saccostrea glomerata and a deep sea sponge Geodia barretti. My research established a strong relationship between lysosomal membrane stability in oysters, reproductive effects and contaminant exposure associated with re-suspended sediments. In the Sydney rock oyster, the relationships between lysosomal membrane stability and contaminant exposure were consistent across multiple estuaries. In contrast, measurements of other cellular biomarkers, lipid peroxidation and glutathione, were inconsistent and of no clear ecological relevance.
The application of cellular biomarkers for distinguishing the effects associated with re-suspended contaminated sediments and drilling discharge, confirmed that suspended contaminants are a potential source of exposure and threat to filter feeding organisms. Re-suspended contaminated sediments and a major component of drilling discharge, barite, were toxic to oysters and sponges respectively. The observed cellular toxicity increased with an increase in total suspended solids (TSS), however increasing the amount of clean TSS had no impact on cellular responses in these organisms.
In summary, this is the first study to evaluate the consistency and ecological relevance of cellular biomarker responses to anthropogenic contaminants in the Sydney rock oyster, Saccostrea glomerata and deep sea sponge, Geodia barretti. My research has highlighted that lysosomal membrane stability responses in these organisms may provide a very useful line of evidence for both exposure and effects in environmental monitoring programs.