Graduate Theses & Dissertations

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Automated Separation and Preconcentration of Ultra-Trace Levels of Radionuclides in Complex Matrices by Online Ion Exchange Chromatography Coupled with Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
Radionuclides occur in the environment both naturally and artificially. Along with weapons testing and nuclear reactor operations, activities such as mining, fuel fabrication and fuel reprocessing are also major contributors to nuclear waste in the environment. In terms of nuclear safety, the concentration of radionuclides in nuclear waste must be monitored and reported before storage and/or discharge. Similarly, radionuclide waste from mining activities also contains radionuclides that need to be monitored. In addition, a knowledge of ongoing radionuclide concentrations is often required under certain ‘special’ conditions, for example in the area surrounding nuclear and mining operations, or when nuclear and other accidents occur. Thus, there is a huge demand for new methods that are suitable for continuously monitoring and rapidly analyzing radionuclide levels, especially in emergency situations. In this study, new automated analytical methods were successfully developed to measure ultra trace levels of single or multiple radionuclides in various environmental samples with the goal of faster analysis times and less analyst involvement while achieving detection limits suitable for typical environmental concentrations. Author Keywords: automation, ICP-MS, ion exchange, radionuclide
Electrochemical Biosensors for Neurodegenerative Disease Biomarkers
The onset of neurodegenerative diseases such as Alzheimer’s disease (AD) and amyotrophic lateral sclerosis (ALS) are typically characterised by the aggregation of protein biomarkers into cytotoxic fibrils. Novel means of analysing these biomarkers are needed to expand the literature toward earlier diagnosis of these conditions. Electrochemical sensors could offer the sensitivity and selectivity needed for specialised analysis, including potential point-of-care applications. The AD biomarker Tau, and ALS biomarker TDP-43 proteins are explored here by using a label-free electrochemical sensors. Tau protein was covalently bound to gold electrode surface to study the in vitro mechanisms of aggregation for this protein. An immunosensor to TDP-43 was developed by covalently binding primary TDP-43 antibodies (Abs) on gold electrode surface. A novel direct ELISA sensor for TDP-43 with visual detection and electrochemical quantification was also developed. The results validated the experimental designs toward specialised and selective analysis of these biomarkers and their aggregation mechanisms. Author Keywords: ALS, Alzheimer's, Biosensors, Electrochemistry, Tau, TDP-43
Evaulating the American Woodcock Singing-Ground Survey Protocol in Ontario using Acoustic Monitoring Devices
The breeding phenology of American Woodcocks (Scolopax minor) was evaluated in Ontario, Canada to determine if changes in dates of courtship activity have introduced negative bias into the American Woodcock Singing-ground Survey (SGS). Long-term woodcock phenology and climate data for Ontario were analysed using linear regression to determine if woodcock breeding phenology has changed between 1968 and 2014. There was no significant trend in woodcock arrival date, but arrival date was correlated with mean high temperature in March. In 2011-2013, programmable audio-recording devices (song meters) were deployed at known woodcock singing-grounds to determine if peaks in courtship activity coincided with survey dates used by the SGS. Spectrogram interpretation of recordings and data analyses using mixed-effects models indicated the SGS survey dates were still appropriate, except during the exceptionally early spring in 2012 when courtship displays were waning in one region during the survey window. The methods for interpretation of song meter recordings were validated by conducting point counts adjacent to song meters deployed at singing-grounds, and at randomly selected locations in woodcock habitat. Recommendations for the SGS protocol are included. Author Keywords: detectability, phenology, Scolopax minor, Singing-ground Survey, song meter
Nutrient Metabolism of an Aquatic Invertebrate and its Importance to Ecology
Aquatic consumers frequently face nutritional limitation, caused in part, by imbalances between the nutrients supplied by primary producers and the metabolic demands of the consumers. These nutritional imbalances alter many ecological processes including consumer life-history traits, population dynamics, and food web properties. Given the important ecological role of organismal nutrition, there is a need to have precise and specific indicators of nutritional stress in animals. Despite this need, current methods used to study nutrition are unable to distinguish between different types of nutritional limitation. Here I studied nutritional metabolism in the freshwater zooplankter, Daphnia. A greater understanding of nutritional metabolism would allow for the development of dietary bio-indicators that could improve the study of the nutritional ecology of animal consumers. Specifically, I addressed the question: What affects the biochemical composition of a generalist aquatic consumer? My overall hypothesis was that the quantity and quality of the diet affects the biochemical composition in a nutrient specific manner. To test this hypothesis, I examined various response variables involved in nutrient metabolism such as alkaline phosphatase activity, whole metabolome, and free amino acid composition. For each response variable, I grew Daphnia under various nutritional stressors and determined if responses are nutrient specific or are a general stress response. I found the current method of measuring alkaline phosphatase was not a phosphorus specific indicator, as activity increased in all nutrient stressed treatments. Analyzing the whole metabolome resulted in nutritional stressors being separated in multivariate space, with many identified metabolites being significantly different from nutrient rich Daphnia. Upon further examination the daphnids free amino acids profiles are caused by differences between the supply of amino acids from the algae and the demand within the Daphnia. These differences in supply and demand resulted in the ability to classify the nutritional status of Daphnia with the use of discriminant analysis, a classification multivariate model. In addition to a deeper understanding and advanced knowledge of the physiological changes caused by nutrient limitation, this research has provided strong evidence for the application of nutritional biomarkers/profiles to identified the nutritional status of Daphnia. Author Keywords: Bio-indictor, Ecological stoichiometry, Metabolism, Nutritional limitation, Nutritional status
Diversity, Biogeography, and Functional Traits of Native Bees from Ontario’s Far North and Akimiski Island, Nunavut
Bees (clade Anthophila), are poorly studied in northern Canada, as these regions can be difficult to access and have a short growing season. This study examined bees from two such regions: Ontario’s Far North, and Akimiski Island, Nunavut. I present this study as the largest biogeographical study of bees performed in these remote areas to enhance knowledge of northern native bees. I found 10 geographically unexpected species in Ontario and on Akimiski Island. Rarefaction and the Chao 1 Diversity Index showed that Akimiski is nearly as diverse as the Far North of Ontario, a significantly larger area. I also found, based on log femur length versus latitude, Bombus worker size was consistent with Bergmann’s rule, and there were no apparent statistical differences in the community weighted means of functional traits between the Far North’s Boreal Shield and Hudson Bay Lowlands ecozones. This work provides invaluable knowledge of the native bee species from these regions, which has implications for their future conservation. Author Keywords: Akimiski Island, Bergmann's rule, Chao 1, Community-weighted means, native bees, rarefaction
Responses of Primary Producers and Grazers to Silver Nanoparticle Exposure
The increasing production and use of silver nanoparticles (AgNPs) raise concerns on environmental exposure and impact. A large scale in situ enclosure study was conducted at the Experimental Lakes Area to determine the effect of AgNPs on natural phytoplankton and zooplankton communities. This study investigated AgNPs of varying concentrations (4, 16 and 64 μg/L), dosing regimens (chronic vs. pulse), and capping agents (poly-vinyl pyrrolidone vs. citrate). Phytoplankton communities were influenced only by the natural limnological properties of the system signifying tolerance to AgNPs. Zooplankton community structure significantly changed with AgNP concentration and dosing regimen indicating AgNP sensitivity. A microcosm study investigating the effect of AgNPs and phosphorus-dosed periphyton before and after grazing by two benthic invertebrate species (snails and caddisfly larvae) showed reduced periphyton stoichiometry with AgNP exposure. Grazers foraged less on silver dosed periphyton indicating a preferential choice in food quality. Phosphorus reduced the detrimental effects of AgNPs across all conditions. These studies verify the need for in situ experimental designs to fully investigate the effects of AgNPs and their interaction with environmental factors, multiple species assemblages, and across trophic levels. Author Keywords: benthic invertebrate, Experimental Lakes Area, periphyton, phytoplankton, silver nanoparticles, zooplankton
Expression of Giardia intestinalis flavoenzyme GiOR-1 and characterization of its electron transfer properties
Giardia intestinalis possesses four isotypes of cytochrome b5 (gCYTB-I-IV) that differ from their mammalian counterparts, suggesting different functions in this protozoan parasite. Although the recently discovered Giardia flavoenzyme, GiOR-1, reduces these cytochromes, its properties have not been thoroughly studied, owing to the difficulty in its expression. Here I describe successful conditions for expression of GiOR-1 using autoinduction. GiOR-1 is obtained with flavins bound as indicated by its UV-visible spectrum. Its ability to catalyze electron transfer from donors (NADH, NADPH) to acceptors (oxygen, ferricyanide, cytochrome c, gCYTB5-III) were studied in spectrophotometric rate assays. NADPH is the preferred electron donor, while cytochromes are the preferred electron acceptors. Interestingly, the His-tag used to purify gCYTB5-III decreases its reaction rate with GiOR-1, as an untagged version has slightly faster rates. These findings establish the appropriate conditions for further studies on GiOR-1, including the identification of endogenous electron acceptors. Author Keywords: Autoinduction, Cytochrome b5, Cytochrome P450 oxidoreductase, Giardia intestinalis, GiOR-1, Polyhistidine tag
Syrphidae (Diptera) of northern Ontario and Akimiski Island, Nunavut
Syrphids, also known as hover flies (Diptera: Syrphidae) are a diverse and widespread family of flies. Here, I report on their distributions from a previously understudied region, the far north of Ontario, as well as Akimiski Island, Nunavut. I used samples collected through a variety of projects to update known range and provincial records for over a hundred species, bringing into clearer focus the distribution of syrphids throughout this region. I also analysed a previously un-tested trap type for collecting syrphids (Nzi trap), and report on results of DNA analysis for a handful of individuals, which yielded a potential new species. Author Keywords: Diptera, Ontario, range extension, Syrphidae
Influence of Nitrogen Deposition on Community Composition in Pinus banksiana Forests Across Northwestern Canada
Anthropogenic atmospheric emissions and subsequent deposition of nitrogen (N) can affect N-sensitive habitats and lead to shifts in plant species community composition. This study assessed the effects of N deposition on plant community composition for Jack pine forests across northwestern Canada and across a smaller subset of sites surrounding the Athabasca Oil Sands Region (AOSR) using ‘gradient forest’ analysis. Predictor influence on community composition varied depending on the scale of the study and relatively distinct thresholds were identified for different plant groups. In the larger scale study, a total deposited nitrogen (TDN) threshold of 1.5 – 3 kg N ha-1yr-1 was well suited to protect predominantly lichen species, consistent with lichen-based critical loads from other studies. Across the smaller scale study, a TDN threshold of 5.6 kg N ha-1yr-1 was primarily associated with vascular species changepoints but did include some important N-indicator lichen and bryophyte species. Author Keywords: critical loads, gradientForest, Jack pine, Nitrogen deposition, species composition
mycobiome and skin chemistry of bat wings in relation to white-nose syndrome
White-nose syndrome (WNS) is a skin disease of bats caused by the fungus Pseudogymnoascus destructans (Pd) that damages flight membranes during hibernation and can lead to death. The disease causes mortality of multiple bat species in eastern North America and is spreading into western North America. Future impacts of WNS on naïve bat populations are unknown. Variation in host susceptibility occurs among and within species, but mechanisms driving this variation are unclear. Multiple studies have characterized immunological responses to WNS, but skin physiology as a barrier to pathogens is understudied. The unique ability of Pd to actively penetrate the normal, intact skin of its mammalian host makes WNS an interesting study system to understand skin defenses. Aspects of the mammalian skin environment that can influence disease susceptibility include pH, sebaceous lipids, and microbiomes. I found skin mycobiomes of WNS-susceptible species had significantly lower alpha diversity and abundance compared to bat species resistant to Pd infection. Using these data, I predicted that most naïve bat species in western North America will be susceptible to WNS based on the low diversity of their skin mycobiomes. Some fungi isolated from bat wings inhibited Pd growth in vitro, but only under specific salinity and pH conditions, suggesting the microenvironment on wings can influence microbial interactions and potentially WNS-susceptibility. I measured the wing-skin pH of bats in eastern Canada and found that Eptesicus fuscus (WNS-tolerant) had more acidic skin than M. lucifugus (WNS-susceptible). Differences in sebum quantity and composition among and within mammalian species may help explain variation in skin disease susceptibility and the composition of skin microbiomes. This is due to the antimicrobial properties of sebum and the use of sebum as a nutrition source by microbes. Outcomes of this work further our understanding of inter- and intra-specific differences among bat species and individuals in skin mycobiomes and physiology, which may contribute to variation in WNS-susceptibility. Future research should focus on characterizing the physical and chemical landscape of skin as this is essential for understanding mechanisms structuring skin microbial assemblages and skin disease susceptibility in wildlife. Author Keywords: bat, fungi, microbiome, mycology, physiology, white-nose syndrome
HABITAT SELECTION AND LIFE-HISTORY TRAITS OF BREEDING BIRDS IN THE BOREAL-TUNDRA ECOTONE, WITH SPECIAL ATTENTION TO THE AMERICAN ROBIN (TURDUS MIGRATORIUS)
I investigated biodiversity of birds and vegetation associations along the boreal-tundra ecotone in Ivvavik National Park, Yukon Territory, and breeding adaptations used by American Robins (Turdus migratorius) at high latitudes. Twenty bird species were detected over three years using point-count surveys. Densities of American Robin, Dark-eyed Juncos (Junco hyemalis), and Yellow-rumped Warbler (Dendroica coronata) had positive relationships with tree and shrub density, whereas density of White-crowned Sparrows (Zonotrichia leucophrys) was negatively related to tree density. American Robins at this latitude raised only one brood, but females laid slightly larger clutches, the young fledged earlier, and pairs experienced higher nest-success than American Robins at more southerly latitudes. American Robins selected nest sites with high vegetation volume, at both the nest-site, and the nest-patch. This study is important for the first description of the bird community at this high latitude location, and describing how a species at the northern limit of the boreal forest has adapted to living with short-breeding seasons. Author Keywords: American Robin, Ivvavik National Park, Life History, Nest-stie selection, Northern limit
Effect of Carbon Source and Phytohormones on the in vitro Growth of Euglena Gracilis
Microalgae are a promising source of valuable compounds relevant to biofuels, biomaterials, nutraceuticals as well as animal and human nutriment. Unfortunately, low cell density and slow growth result in reduced economic feasibility. Heterotrophic cell culturing using an organic carbon source in lieu of light has proven to be an effective alternative to photobioreactors; however, further improvement may be possible with the addition of growth promoting phytohormones. In this thesis, growth and endogenous hormone profiles in heterotrophic cultures of Euglena gracilis were evaluated using glucose and ethanol as carbon sources. Cytokinin (CK) and abscisic acid (ABA) were quantified by HPLC-ESI-MS/MS and compared to culture growth dynamics. Exogenous phytohormones treatments were also conducted to determine if they may mitigate nutrient reduction and improve growth. Phytohormones CK and ABA were purified and analyzed at seven points along the growth curve in small scale (250 mL flasks, 100 mL working volume) cultures. Among the key findings was that ethanol cultures undergoing exponential growth, primarily synthesize freebase cytokinins (FBCKs) and methylthiol-cytokinins (MeSCKs), while not producing detectable levels of ABA. In exogenous studies, dry biomass was positively influenced with the addition of exogenous ABA; however, the most notable result revealed the ability of transZ to alleviate nutrient reduction. These findings suggest a communication network in algal culture using FBCKs and MeSCKs, as well as the potential for exogenous hormone supplementation to increase growth rates and overall biomass productivity. Author Keywords: abscisic acid, cytokinin, Euglena gracilis, heterotrophy, phytohormones

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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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