Zoology - Theses
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ItemThe effects of copper antifouling paints and marinas on the ecology of marine sessile epifaunal assemblages(University of Melbourne, 2000)An experimental field study was undertaken to evaluate the effects of copper dosed from antifouling paints on the development of sessile epifaunal fouling assemblages in southeastern Australia. The study system was chosen because of the importance of copper pollution in the marine environment and the fact that members of assemblages of this type are the target organisms of antifouling compounds. Experiments were conducted inside and outside of enclosed marinas, as it was hypothesised that the conditions found inside marinas may have led to differential effects of copper dose in this environment. Initially, I developed a system to dose copper to settlement plates in the field. After several pilot experiments, I chose a system that used a laboratory-made antifouling compound painted onto a collar around a settlement plate as the dosing method. Field tests established that this system exerted biological effects over the settlement plates, and that these effects lasted for at least four weeks. Field-measurement at four sites, of copper doses delivered to plates demonstrated that dose differed among sites and times of year. The difference appeared to be in part related to the amount of water movement. A field-study that compared fouling assemblages developing in two marinas near Melbourne, Victoria to assemblages at each of three nearby control sites, confirmed that the marinas affected assemblage structure. For each marina, a number of species showed an effect, but very few species showed the same effects across both marinas. After aggregation of the species to functional groups, some effects were found across both marinas. Three approaches were undertaken to investigate the effects of dosed copper and the marinas on establishment of sessile epifaunal assemblages. The first experiment examined early recruitment of assemblages and found that copper dose affected a number of species recruiting to the plates. Recruitment varied widely with time and between sites inside and outside the marinas, but the results seemed to reflect normal temporal and spatial heterogeneity characteristic of the recruitment of fouling organisms. The second approach examined growth rates and competitive abilities of colonial fouling organisms. By using clonal replicates of colonies, I was able to show that the populations studied showed heterogeneity in growth rates, and occasionally showed heterogeneity in the effects of treatments on growth rates. Partially as a result of this variability, significant treatment effects on growth rates were rare. I did not find any effects of dose or marinas on the competitive ability of colonies, but the number of experiments that examined this feature was very low. Finally, a longer-term experiment that utilised reciprocal transplants of plates between sites and doses showed that effects of the marinas on assemblages were more important than effects of dose. Once again, some results indicated that some species showed variability in the degree to which different populations were affected by treatments. Overall, I found that locations (inside or outside the marina) had a greater effect on determining the assemblage structure than did dosed copper, despite these dosing levels being well above background levels of copper in these marinas. This is probably due to a large number of factors associated with marinas over and above increased background heavy metal pollution. Several taxa appeared to show adaptation to local conditions or copper doses, and some appeared to show either heterogeneity in response to dosing or an ability to acclimate to dose. These types of findings have important implications for the manner in which we apply the findings of traditional laboratory-based ecotoxicology experiments to environmental management.