Graduate Theses & Dissertations

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Effects of Silver Nanoparticles on Lake Bacterioplankton
Silver nanoparticles (AgNP) released into aquatic environments could threaten natural bacterial communities and ecosystem services they provide. We examined natural lake bacterioplankton communities' responses to different exposures (pulse vs chronic) and types (citrate and PVP) of AgNPs at realistic environmental conditions using a mesocosm study at the Experimental Lakes Area. An in situ bioassay examined interactions between AgNPs and phosphorus loading. Bacterial communities exposed to high AgNP concentrations regardless of exposure or capping agent type accumulated silver. We observed increases in community production during additions of polyvinylpyrrolidone (PVP) -capped AgNPs and that site and nutrient-specific conditions are important to AgNPs toxicology in aquatic systems. Toxicological effects of AgNP are attenuated in natural conditions and differ from results from laboratory studies of AgNP toxicity. Our results demonstrate more studies are needed to fully assess the risk posed by these novel chemicals to the environment. This work could be useful in forming risk assessment policies which are largely based on lab studies and typically demonstrate strong toxic effects. Author Keywords: bacterial production, bacterioplankton communities, ecological stoichiometry, Experimental Lakes Area, mesocosms, silver nanoparticles
Observation-based assessment of atmospheric sulphur surrounding a major aluminum smelter in British Columbia, Canada
Recent developments at an aluminum (Al) smelter in Kitimat, BC resulted in a permitted increase of 27 to 42 tonnes of sulphur dioxide (SO2) emissions per day. Gaseous SO2 is a pollutant known to contribute to acidic deposition through processes of wet and dry deposition and can additionally react in-atmosphere to form particulate sulphate (pSO42-). Between June 2017 to October 2018, an extensive network consisting of ion exchange resin (IER) column, passive-diffusive, and active filter-pack samplers was established to provide an estimate of total annual S deposition and pSO42- variation throughout the Kitimat Valley. Filter-pack sampling determined the relative concentration of pSO42- increased downwind of the smelter. Comparison of observation-based and modelled total annual deposition suggested CALPUFF was accurate in representing the spatial viability of S deposition (R2 = > 0.85). However, the model appeared to overpredict near-field deposition suggesting the potential of underestimation further downwind of the smelter. Author Keywords: aluminum smelter, atmospheric deposition, filter-pack sampler, ion-exchange column sampler, pSO42-, SO2
Maya Exploitation of Animal Resources during the Middle Preclassic Period
This study examines the foraging strategies of animal resource exploitation during the Middle Preclassic period (900-300 BC) at the ancient Maya site of Pacbitun, Belize. The faunal remains analyzed in this study were recovered from various domestic structures associated with the production of shell artifacts. Detailed taphonomic analyses have revealed that the Pacbitun faunal remains were particularly affected by weathering and density-mediated attrition. White-tailed deer was the prey most frequently acquired by the Middle Preclassic Maya of Pacbitun, followed by other lower-ranked artiodactyls. A variety of less profitable prey were sometimes included in the diet breadth. Using the central place forager prey choice model as a framework, the analysis of diet breadth, habitat use, and carcass transport patterns suggests that most animal resources were acquired from terrestrial habitats, at short distances from the site. Complete carcasses of large game appear to have been frequently transported to the site, where they were exploited for their meat and marrow. Comparisons with other Middle Preclassic faunal assemblages indicate significant differences in terms of taxonomic composition, with an emphasis on the procurement of fish and turtles. It is suggested that the Middle Preclassic Maya adopted foraging strategies focusing on the exploitation of local habitats, with occasional use of exotic resources. Author Keywords: Animal, Belize, Foraging, Maya, Subsistence, Zooarchaeology
Effect Assessment of Binary Metal Mixtures of Ni, Cu, Zn, and Cd to Daphnia magna
Mixtures of metals occur in surface waters, toxicity of which has drawn world-wide attention due to their crucial role in both ecotoxicology and regulations. The present research was undertaken to study the acute toxicity of binary mixtures of Ni, Cu, Zn, and Cd to the freshwater organism, Daphnia magna. The experimental approach included single and binary metal toxicity tests based on the 48h acute toxicity bioassay of Environment Canada. The acute toxicity of single metals followed the order of Cd > Cu > Zn > Ni. Based on the calculated 48h EC50 value of single metals, a toxic unit (TU) approach was used to combine two metals in a binary mixture, in which 1TU was equal to the 48h EC50 value of a metal in single exposure. The toxicity of binary metal mixtures to D. magna followed the order of Cu-Cd > Cu-Zn > Zn-Cd > Cu-Ni > Zn-Ni > Cd-Ni, which demonstrated three types of toxicity (i.e., less than additive, additive, and greater additive). Predictions from additivity models (including concentration addition (CA) and independent action (IA) models), a generalized linear model (GLM), and a biotic-ligand-like model (BLM-like) were compared to the bioassay results. The CA and the RA models also predicted three types of toxicity of the binary metal mixtures (i.e., less than additive, additive, and greater than additive). However, the CA model mostly overestimated the toxicity of binary mixtures. Predictions from the GLM supported the inclusion of the interaction between two metals in a mixture to predict the toxicity of binary metal mixtures. The binary metal toxicity was also predicted using a BLM-like model based on the calculated concentrations of free ionic forms of the metals, affinity constants, and toxic potency of each metal. In this model, it was hypothesized that the toxicity of metal mixture is the result of competition of metals with Ca2+ at biotic ligands, which can lead to whole-body deficiency of Ca2+ in D. magna. The BLM-like model provided the toxic potency of single metals with the following order, Cu > Cd > Zn > Ni. Although the prediction of the BLM-like model was not in good agreement with the observed toxicity of binary metal mixtures, an overestimation of risk of mixture toxicity was obtained using this model, which could be promising for use in environmental risk assessment. Author Keywords: biotic ligand model, concentration addition, Daphnia magna, independent action, metal toxicity, modeling
Assessment of an adult lake sturgeon translocation (Acipenser fulvescens) reintroduction effort in a fragmented river system
North American freshwater fishes are declining rapidly due to habitat fragmentation, degradation, and loss. In some cases, translocations can be used to reverse local extirpations by releasing species in suitable habitats that are no longer naturally accessible. Lake sturgeon (Acipenser fulvescens) experienced historical overharvest across their distribution, leading to endangered species listings and subsequent protection and recovery efforts. Despite harvest and habitat protections, many populations do not appear to be recovering, which has been attributed to habitat alteration and fragmentation by dams. In 2002, 51 adult lake sturgeon from the Mattagami River, Ontario, Canada were translocated 340 km upstream to a fragmented 35 km stretch of the river between two hydroelectric generating stations, where sturgeon were considered extirpated. This study assessed the translocation effort using telemetry (movement), demographics and genetic data. Within the first year, a portion of the radio-tagged translocated individuals dispersed out of the release area, and released radio-tagged individuals used different areas than individuals radio-tagged ten years later. Catches of juvenile lake sturgeon have increased over time, with 150 juveniles caught within the duration of this study. The reintroduced population had similar genetic diversity as the source population, with a marked reduction in effective population size (Ne). The results indicate that the reintroduction effort was successful, with evidence of successful spawning and the presence of juvenile lake sturgeon within the reintroduction site. Overall, the results suggest adult translocations may be a useful tool for re-establishing other extirpated lake sturgeon populations. Author Keywords: conservation, endangered species, lake sturgeon, reintroduction, telemetry, translocation
Genre Trouble and Extreme Cinema
This dissertation re-evaluates theories of genre and spectatorship in light of a critic-defined tendency in recent art cinema, coined extreme cinema. It argues that the films of Mexican director Carlos Reygadas and French director Catherine Breillat expand our generic classifications and, through the re-organization of the visual presentation of genre-specific clichés and devices, their films transform sense experience and thought. My approach loosely follows Stanley Cavell’s various assertions of film as a medium of thought or, simply, that films think. Reygadas and Breillat allow spectators to reflect on the genre-film experience; I contend that their films make it apparent that genre is not established prior to the viewing of a work but is recollected and assembled by spectators in ways that matter for them. In fostering this experience of collection, these two directors propose a kind of ethics of curatorship: spectators are tasked with collecting and recollecting their film experience to generate particular social, cultural, and political critiques. To further accomplish and foster film as thought, the directors appeal to spectators’ sense experiences. I therefore deploy contemporary film theories on the senses, both phenomenological and affect theory, and partake in close readings of the films’ forms and narratives. The Introduction outlines my intervention in genre theory, discusses the key theoretical texts, develops the phenomenological framework I employ for the chapters to follow, develops my methodology through a description of Cavell’s style, and presents the stakes of my argument. Chapter one considers the place of experimental narrative cinema in Reygadas’s Post Tenebras Lux (2012). I argue that through his realist style, this film aims at an experience for spectators “as if” in a dream and through this film experience I posit the critique I find internal to the film. The second chapter turns to Catherine Breillat’s oeuvre and the confrontation her work poses to conceptions of pornography. I bring her 2001 feature Fat Girl (À ma soeur!) to bear on what I claim to be a new style of pornographic work and its challenge to patriarchy. The final chapter brings together Reygadas’s Battle in Heaven (Batalla en el cielo, 2005) and Breillat’s Sex is Comedy (2002) to accomplish an analysis of sexual performances in otherwise dramatic films. Author Keywords: art cinema, Carlos Reygadas, Catherine Breillat, contemporary cinema, film theory, genre theory
Racism in Argentina and the Blackness Problem. The Change in Perception of Afro-Descendants in Buenos Aires and the New Dimensions of Blackness in Argentina (1880-1930)
This thesis examines racism in Argentina between 1880 and 1930. The governing elite's efforts to whiten the Argentine population at the end of the nineteenth century led to the erasure and discrimination of anyone who did not have Caucasian features: Afro-descendants, mulattos, mestizos, and creoles. However, in the 1930s, whitening policies proved to have limited success. On the one hand, Afro-descendants were praised by the middle and lower classes of Buenos Aires; on the other hand, the Great Depression's effects made it clear that the Argentine population was made up of an ethnic mixture that had much darker skin tones than the whitening elite preferred. This work will show how the impact of the 1930s global crisis, as well as the enthusiasm for Afro-descendants, reinforced the racism that still existed, and will demonstrate that blackness became more than a racial but also a class connotation. Author Keywords: Afro-descendants press, Blackness in Argentina, Buenos Aires Press, Cultural Constructions, Popular Blackness, Racial Identity
mechanistic analysis of density dependence in algal population dynamics
Population density regulation is a fundamental principle in ecology, however there remain several unknowns regarding the functional expression of density dependence. One prominent view is that the patterns by which density dependence is expressed are largely fixed across a species, irrespective of environmental conditions. Our study investigated the expression of density dependence in Chlamydomonas reinhartti grown under a gradient of nutrient densities, and hypothesized that the relationship between per capita growth rate (pgr) and population density would vary from concave-up to concave-down as nutrients became less limiting. Contrary to prediction, we found that the relationship between a population's pgr and density became increasingly concave-up as nutrient levels increased. Our results suggest that density dependence is strongly variable depending on exogenous and endogenous processes acting on the population, implying that expression of density regulation depends extensively on local conditions. Population growth suppression may be attributable to environments with high intraspecific competition. Additional work should reveal the mechanisms influencing how the expression of density dependence varies across populations through space and time. Author Keywords: Chlamydomonas reinhartti, density dependence, logistic model, population dynamics, single species growth, theta-logistic equation
Asserting sexual (dis)interest
Sexual assertiveness encompasses skills in refusing unwanted sexual situations and bringing about wanted sexual situations. Measures of sexual assertiveness typically assess both refusal and initiation aspects, yet there is a dearth of research examining these skills in relation to one another. The present study examined the relationship between these skillsets in women, exploring predictors of each. Initiation and refusal assertiveness were moderately correlated. Additionally, the relationship between them was not entirely explained by general assertiveness, indicating that there is something unique to assertiveness in the sexual context. Committed relationship context and erotophilic disposition specifically predicted initiation assertiveness. Less endorsement of the sexual double standard and fewer approach motivations for engaging in unwanted sex specifically predicted refusal assertiveness. Few differences emerged in predictors of assertiveness types when comparing sexual orientation groups, yet non-heterosexual women reported slightly lower levels of refusal assertiveness. Implications for sexual education, therapy, and future research are discussed. Author Keywords: sexual assertiveness, sexual autonomy, sexual compliance, sexual double standard, sexual satisfaction, sexual self-disclosure
cascading effects of risk in the wild
Predation risk can elicit a range of responses in prey, but to date little is known about breadth of potential responses that may arise under realistic field conditions and how such responses are linked, leaving a fragmented picture of risk-related consequences on individuals. We increased predation risk in free-ranging snowshoe hares (Lepus americanus) during two consecutive summers by simulating natural chases using a model predator (i.e., domestic dog), and monitored hare stress physiology, energy expenditure, behaviour, condition, and habitat use. We show that higher levels of risk elicited marked changes in physiological stress metrics including sustained high levels of free plasma cortisol which had cascading effects on glucose, and immunology, but not condition. Risk-augmented hares also had lowered daily energy expenditure, spent more time foraging, and decreased rest, vigilance, and travel. It is possible that these alterations allowed risk-exposed hares to increase their condition at the same rate as controls. Additionally, risk-augmented hares selected, had high fidelity to, and were more mobile in structurally dense habitat (i.e., shrubs) which provided them additional cover from predators. They also used more open habitat (i.e., conifer) differently based on locale within the home range, using familiar conifer areas within cores for rest while moving through unfamiliar conifer areas in the periphery. Overall, these findings show that prey can have a multi-faceted, highly plastic response in the face of risk and can mitigate the effects of their stress physiology given the right environmental conditions. Author Keywords: behaviour, condition, daily energy expenditure, predator-prey interactions, snowshoe hare, stress physiology
Enhancing post-mortem interval estimates
The growth of immature insects that develop on human remains can be used to estimate a post-mortem interval (PMI). PMI estimate confidence is negatively affected by: larval killing and preservation methods altering their size, limited morphological parameters to assess larval growth and therefore age, and few available alternate species development data. I compared live specimens to preserved specimens of the same development stages to assess the effects of killing-preservation techniques on morphology, and I introduce a new method that uses digital photography to examine maggot mouthparts for stage grading of Phormia regina. Digital photographic methods enable live insects to be quantified and improve approximations of physiological age. I then use these digital methods to produce a growth-rate model for a beetle commonly found on human remains, Necrodes surinamensis, providing data for PMI estimates that was previously unavailable. Author Keywords: Forensic Entomology, Insect development, Morphometrics, Necrodes surinamensis, Phormia regina, Postmortem interval
Thinking High When Feeling Shy
Social anxiety often co-occurs with substance use disorders – various psychological variables, contextual factors, and implicit cognitions may help explain their relationship. This thesis examined whether social anxiety and psychological variables (jointly and independently) helped predict substance use and related problems. It also explored whether social anxiety group membership helped predict implicit cannabis-sedation associations and substance use desirability. A sample of undergraduate student volunteers (N = 65) completed a computer task, questionnaires with anxiety-provoking vignettes, and online questionnaires. Results indicate that fear of negative evaluation and anxiety sensitivity are important predictors of alcohol and cannabis (respectively) use and problems. Social anxiety group was related to increased cannabis desirability in performance contexts. No significant implicit cannabis-sedation associations were identified. Our findings highlight the importance of certain variables in social anxiety and substance use relationships, and considering contextual factors when assessing substance desirability. It also provides preliminary evidence of a novel implicit cannabis-sedation measure. Author Keywords: Coping, Emotion, Implicit Cognition, Social Anxiety, Substance Use

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Graduate student theses produced at Trent University. You may also browse theses and dissertations by year, program, or author.

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