Assessing and understanding ecological changes to fish communities in highly disturbed estuaries

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Copyright: McKinley, Andrew
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Abstract
Marine fish communities are threatened by the interrelated effects of anthropogenic disturbance, habitat modification, and contamination. This thesis examines the ways in which these stressors affect the ecology of fish communities living in estuaries. Using a variety of methods I documented large scale impacts among fish communities in heavily modified vs. relatively unmodified estuaries. First, a comprehensive meta-analysis identified trends and knowledge gaps. Studies on adult fish have generally shown weakly negative impacts from contamination or largely positive impacts where enriching contaminants are present. I conducted two field studies of adult fish, the results of which were broadly consistent with the literature. Surveys of large bentho-pelagic fish using underwater video showed increased abundance of targeted species in heavily modified/nutrient enriched estuaries. However, beach seine surveys of small bodied species indicated little impact on the beach fish community, even where high levels of modification and contamination were detected. Instead, beach fish were highly correlated to physicochemical gradients. This suggests that impacts are highly variable among adult fish, and that both ecological characteristics and habitat preferences play an important role. Prior to this study nearly no research had been published assessing the impacts of stressors on marine larvae. Substantial differences in larval communities were detected in heavily modified areas, including increased abundance and diversity, large shifts in the occurrence of species, and changes to the overall composition of the community. These trends were highly correlated to contamination of trace metals in the sediment and loss of seagrass cover. Impacts on larval fish were greatest among fully estuarine taxa and those with benthic eggs. Lastly, a final project indicated strong impacts from the accumulation of some trace metals (Cu, Zn, and Se) in muscle tissue of Psuedorhombus jenynsii on the relative body size of the species. In combination these results suggest that stressors have their greatest impact at the early stages of a fishes’ life cycle and that many positive impacts exist in heavily modified estuaries (e.g. increased abundance/diversity). Also, my results suggest that ecological characteristics and habitat mediation may play an important role in determining the relative sensitivity of taxa.
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McKinley, Andrew
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Publication Year
2012
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Thesis
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PhD Doctorate
UNSW Faculty
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