School of BioSciences - Theses
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ItemInvestigating freshwater snails Potamopyrgus antipodarum as a suitable test species for ecotoxicological testing of surface water in Australia( 2020)Ecotoxicology studies the fate and effect of chemicals in the ecosystem using scientific approaches. Laboratory tests (e.g. acute and chronic tests) establish dose response relationships between toxicants and the test species. Although laboratory tests provide essential data to understand the potential impact of toxicants in the aquatic environment, they lack environmental realism. In situ tests provide environmental realism by exposing the test organism to toxicants in the aquatic environment. Test species are central in ecotoxicity assays. Molluscs are commonly used in ecotoxicological tests and they are the second largest phylum, have a global distribution, widely abundant in freshwaters, and ecological importance (e.g. as a food source, provides habitat and protection) makes them useful in ecotoxicity tests. This thesis used a freshwater snail, Potamopyrgus antipodarum (J.E. Gray, 1843), for laboratory and field testing. Although native to New Zealand, it is a successful invasive species in many parts of the world, including Australia and has been successfully used as a test species for ecotoxicity tests and as a bioindicator in some countries (e.g. in Europe, and the USA). A few Australian studies have used it in laboratory assays and field studies. There is still less knowledge and information of P. antipodarum as a test species and bioindicator in Australia. Therefore, the overall aim of the thesis is to assess the potential of P. antipodarum as a bioindicator of freshwater pollution in Australia. In Chapter 2, adult P. antipodarum were exposed (96 h) to environmentally relevant concentrations (ERCs) of metals (copper and zinc) and a pesticide (imidacloprid) in water. Mortality (LC50) and behavioural responses (EC50) were assessed to investigate the sensitivity of the snail and the potential use of its behavioural response in the environmental risk assessment of toxicants. The Chapter 3 was an extension of the Chapter 2 to assess their sensitivity in chronic toxicity tests. Adult snails were exposed for 28-d to ERCs of several chemicals (Cu, Zn, bifenthrin, and 17 a-ethynylestradiol), physico-chemical conditions (salinity and temperature), and food limitation in water and sediment bioassays. Endpoints including reproduction, growth, and mortality were measured. This study evaluated the sensitivity of this species during chronic exposure and compared the response of these Australian cultures to those abroad. In Chapter 4, adult snails were deployed in cages in the field for 28-d at 9 sites (i.e. 7 impact sites, and 2 reference sites) in Merri Creek and an additional reference site in Cardinia Creek to evaluate the performance of snails at various points along Merri Creek with different land use. Various endpoints were measured at the organism level (growth, mortality and reproduction), and the sub-organism level (glutathione Stransferase, GST; lipid peroxidation, LPO; and catalase, CAT). The biological response of the snails at each impact site were compared to the 2 reference sites on Merri Creek to show the potential impact of land use on the snails. The additional reference site at Cardiana Creek was compared with the reference sites on Merri Creek to identify any difference in response in a different catchment. This project shows that P. antipodarum is a suitable and sensitive species for acute and chronic assays because it responded to ERCs of toxicants, the response is like populations abroad, it showed a similar response to other test species and LC50 and EC50 value was within the range of other test species in use. There is potential to use acute tests (LC50) and behavioural responses (EC50) in the rapid risk assessment of environmental pollutants. Field data also revealed that P. antipodarum is a suitable bioindicator for Australian environmental conditions because the response of this population was similar to the populations abroad, and other test species used in in situ tests and showed a high tolerance to environmental variations. This research also shows that although laboratory tests can provide us with essential data to understand the potential impact of toxicants in the aquatic environment, they lack environmental realism. And we can achieve environmental realism by exposing the species to toxicants in the aquatic environment during in situ tests.