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Biological invasions are among the leading causes of species diversity loss; however, the impacts of invasion are context-dependent and can vary with the local environment. The mechanisms governing variation in impact and their relationship to specific abiotic and biotic factors remain largely unexplored. Recent local declines in native unionid mussels have been attributed to the invasion of North American lakes and rivers by the Eurasian zebra mussel ( Dreissena polymorpha), as a result of intense fouling of unionid shells by zebra mussels. My research investigated the role of abiotic and biotic factors in mediating the impact of zebra mussels on native mussels. I examined the impact of zebra mussels on unionids in a habitat thought to be suboptimal for zebra mussels and compared this to the impact observed in other invaded habitats. A predictive model relating fouling intensity to local environmental variables (calcium concentration, sediment particle size) was developed, and a predator-exclusion experiment was conducted to investigate the role of predation in mediating fouling intensity. Overall, I found that two abiotic factors of the local environment were significant predictors of fouling intensity and that relationships used to predict the impact of zebra mussels could be extended to a broader range of habitats.

The goal of this thesis was to examine the sources and ecological behaviour of genotoxic organics in the St. Lawrence river system. A rapid and effective version of the SOS Chromotest was developed to accomplish the task of genotoxicity assessment. The method, validated with standard reference materials, is particularly well suited to complex environmental extracts. The endpoint investigated throughout the thesis, SOS genotoxicity, is empirically related to more familiar endpoints such as mutagenicity and carcinogenicity. Analyses of literature data confirmed correlations between SOS genotoxicity and both Ames/Salmonella mutagenicity and animal carcinogenicity. Analyses of industrial and municipal wastewaters revealed that organic and inorganic chemical production facilities, metal refining and founding facilities and petroleum refineries release high potency wastes. Loading values indicate that low potency sources (e.g. municipal wastewater and pulp & paper facilities) often have exceptionally high loadings. A substantial portion (2.3-99.8%) of industrial genotoxins are associated with suspended particulates. Sorption partition efficients (K$ sb{ rm d-genotox}$) indicate that municipal wastewater and pulp & paper facilities release particularly soluble genotoxins. Extracts of suspended particulate matter collected near industrial discharges are direct-acting. Bottom sediment extracts are less potent and usually require S9 metabolic activation. Genotoxicity of both bottom sediment and suspended particulates are empirically related to the genotoxicity of regional industrial emissions. Direct-acting substances in the water column appear to be less stable and may be converted to more stable pro-genotoxic substances present in the bottom sediments. A mass balance of genotoxicity for St. Lawrence surface waters revealed that domestic, rather than industrial sources make the largest contribution to observed genotoxicity. The importance of domestic wastes was confirmed

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Using the techniques of microhistory, this thesis explores questions of construction of identity, and the relationship of narrative to identity. The thesis follows the lives of several residents of the St. Lawrence valley as they learn about the residents of New York and New England through business, marriage, adoption and trade in furs. Using case studies of seventeenth-century native and European individuals, as well as information from folklore, parish registers, letters and legal documents, movement in the border region between settled colonies is examined. A nominal index describes the origins of, and provides capsule biographies for, 694 residents of New France whose roots were neither in France nor in the native communities. An examination of these cases allows a comparison between personal choice and social constraint in a colonial context.

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As a result of the legacy of industrial contamination over the last century, areas of sediment deposition in the St. Lawrence River at Cornwall, ON, contain high concentrations of mercury (Hg). The popular sport-fish species, yellow perch (Perca flavescens) and walleye (Sander vitreus) have been found to contain mercury concentrations exceeding Ontario Ministry of Environment consumption guidelines. Interestingly, a paradox exists between two contaminated sites – despite elevated sediment Hg concentrations at Zone 2, fish from Zone 1 contain higher Hg concentrations. Further research has indicated that these patterns of Hg were not attributed to growth rate, condition factor, diet composition, or trophic position of yellow perch. Rather, Hg concentrations in yellow perch may be described by the heterogeneity of prey contamination and fish bioenergetics. As a result of the paradox between total Hg (THg) concentrations in sediments and biota between two contaminated sites, it was necessary to examine the benthic invertebrate community and how it may transfer Hg from sediments to yellow perch. This apparent paradox now extends to all prey items, since prey items from the stomach contents of yellow perch caught in Zone 1 were significantly more contaminated than those of Zone 2. Use of δ15N and δ13C, measures of trophic position and energy source, respectively, indicated that prey selection, but not food chain length, may also be an important factor in explaining the variation in Hg burdens in yellow perch. Small-scale patterns of biomagnification, as shown by a comparison of δ15N and logTHg, indicated that the rates of biomagnification were similar among zones, but the amount of THg present at the base of the food web was twice as high at Zone 1 as at other contaminated sites. Overall, the relative importance of vertical and horizontal food web structure changed spatially and temporally, highly influencing THg concentrations of prey items and yellow perch. / Thesis (Master, Biology) -- Queen's University, 2007-08-02 08:02:40.26

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