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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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The behaviour of Surf Scoters (Melanitta perspicillata ) was studied on staging grounds in spring of 2006 and compared to behaviour on moulting grounds later that summer. Moulting Surf Scoters have a distinct activity pattern in comparison to those on spring staging grounds. During moult, foraging occurs mainly in the morning and evening, whereas during the spring a similar proportion of birds foraged at all periods of the day. Birds having recently initiated moult foraged significantly less that on staging grounds. However, as moult progressed, this discrepancy disappeared. / In addition, we tracked the movements of flightless Surf Scoters using satellite telemetry during the 2006 wing-moult period. Despite their reduced mobility, Surf Scoters are able to swim long distances while flightless. However, the majority of their activities are carried out within small core areas. This study also indicates that satellite telemetry can be used effectively to track the daily movements of wildlife.