Graduate Theses & Dissertations

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significance of topographically-focused groundwater recharge during winter and spring on the Oak Ridges Moraine, southern Ontario
The Oak Ridges Moraine (ORM) is a key hydrogeologic feature in southern Ontario. Previous work has emphasized the importance of depression-focused recharge (DFR) for the timing and location of groundwater recharge to the ORM’s aquifers. However, the significance of DFR has not been empirically demonstrated and the relative control of land cover, topography, and surficial geology on DFR is unclear. The potential for DFR was examined for topographic depressions under forested and open, agricultural land covers with similar soils and surficial geology. Recharge (R) was estimated at the crest and base of each depression during the 2012-13 and 2013-14 winter-spring periods (~December – May) using both a 1-dimensional water balance approach and a surface-applied Br- tracer. At each depression, air temperatures, precipitation, snow depth and water equivalent, soil water contents, soil freezing, and depression surface-water levels were monitored and soil properties (texture, bulk density, porosity, and hydraulic conductivity) were measured. Both forested and agricultural land covers experienced soil freezing; however, concrete frost did not develop in the more porous and conductive forest soils. Concrete frost in agricultural depressions resulted in overland flow, episodic ponding and drainage of rain-on-snow and snowmelt inputs. Recharge was an order-of-magnitude greater at the base of open depressions. Observations of ponding (as evidence of DFR) were made at an additional 14 depressions with varying land cover, geometry, and soil type during the 2014 snowmelt period and measurements of pond depth, pond volume, land cover (i.e., percentage of agricultural vs. forested cover), depression geometry (i.e., contributing area, average slope, relief ratio) and soil texture were made. Ponding was restricted to depressions under mostly agricultural cover and a positive, non-linear relationship between pond volume and average slope was shown for sites with similar land cover and soil texture, but neither pond depth nor volume were related to any other depression characteristics. Results suggest that DFR is a significant hydrologic process during winter and spring under agricultural land cover on the ORM. Topographic depressions under agricultural land cover on the ORM crest may serve as critical recharge “hot spots” during winter and spring, and the ability of the unsaturated zone beneath these depressions to modify the chemistry of recharging water deserves further attention. Author Keywords: Concrete frost, Depression-focused groundwater recharge, Oak Ridges Moraine, Ponding, Topographic depressions, Water balance
role of corticosterone in breeding effort and reproductive success in tree swallows
Glucocorticoids (e.g., corticosterone (CORT)) are hypothesized to mediate decisions regarding reproductive investment during breeding, but the directionality of the relationship is not clear. The CORT-fitness hypothesis posits that high levels of CORT arise from challenging environmental conditions in which an individual will conserve resources for future reproduction or self-maintenance, and thus result in lower reproductive success (a negative relationship). In contrast, the CORT-adaptation hypothesis suggests that, during energetically demanding periods, CORT will mediate physiological or behavioural changes that result in increased reproductive investment and success (a positive relationship). Inconsistencies arise due to the various species and life-history stages studied, and the complex interactions between fitness and glucocorticoids. Using an experimental approach, I investigated the relationship between CORT and reproductive success by manipulating baseline CORT levels in female tree swallows Tachycineta bicolor prior to laying using silastic implants. Implants failed to raise CORT levels of females during either incubation or the nestling stage, and maternal treatment had no effect on indices of fitness at either stage. Using a correlative approach, partial support for the CORT-adaptation hypothesis was found: There was a positive relationship between CORT and hatching success. This only occurred when CORT was measured during incubation, when baseline CORT levels may stimulate increased reproductive effort and success. In contrast, during the nestling stage baseline CORT levels were not related to reproductive investment or success. Maternal CORT levels during incubation also did not influence nestling phenotype, although nestling stress CORT levels were higher in individuals that survived to fledging. In conclusion, CORT mediates reproductive effort and success during some breeding stages, but it is still unclear why this is the case and whether this same pattern will prevail in other contexts. Author Keywords: corticosterone, HPA axis, maternal effects, reproductive success, tree swallow
role of Cln5 in autophagy, using a Dictyostelium discoideum model of Batten disease
This thesis investigated the role of the neuronal ceroid lipofuscinosis protein, Cln5, during autophagy. This was accomplished by performing well-established assays in a Dictyostelium cln5 knockout model (cln5-). In this study, cln5- cells displayed a reduced maximum cell density during growth and impaired cell proliferation in autophagy-stimulating media. cln5- cells had an increased number of autophagic puncta (autophagosomes and lysosomes), suggesting that autophagy is induced when cln5 is absent. cln5- cells displayed increased amounts of ubiquitin-positive proteins but had no change in proteasome protein abundance. During the development of cln5- cells, fruiting bodies developed precociously and cln5- slug size was reduced. Lastly, when cln5- cells were developed on water agar containing ammonium chloride (NH4Cl), a lysosomotropic agent, the formation of multicellular structures was impaired, and the small slug phenotype was exaggerated. In summary, these results indicate that Cln5 plays a role in autophagy in Dictyostelium. The cellular processes that regulate autophagy in Dictyostelium are similar to those that regulate the process in mammalian cells. Thus, this research provides insight into the undefined pathological mechanism of CLN5 disease and could identify cellular pathways for targeted therapeutics. Author Keywords: Autophagy, Batten disease, Cln5, Dictyostelium discoideum, NCL
review of the first- and second-year experience of a group of Trent University students admitted below admission requirements
This study used qualitative research methods to explore the first- and second-year experiences of Trent University students who were admitted below admission requirements in September 2015. Through review of an on-line questionnaire completed by 13 students and two-rounds of semi-structured interviews completed by 5 students, information was gathered on the students’ experiences, specifically regarding self-efficacy for academic achievement, self-efficacy for self-regulated learning, locus of control, student engagement, and sense of belonging. The major findings of this case study were grouped into four driving themes: self-awareness as a learner, goal-setting and motivation, the Trent community, and course experience. Participants of the study felt that the inclusive social and learning environments at Trent University enhanced their sense of belonging within the university community. These findings are not meant to be generalized, as they arose from this specific group of students at Trent University. Author Keywords: first-year experience, locus of control, post-secondary, self-efficacy, sense of belonging, student engagement
regional comparison of the structure and function of benthic macroinvertebrate communities within Precambrian Shield and St. Lawrence lowland lakes in south-central Ontario
Benthic macroinvertebrtes (BMI) are functionally important in aquatic ecosystems; as such, knowledge of their community structure and function is critical for understanding these systems. BMI were sampled from ten lakes in each of two regions of south-central Ontario to investigate which chemical and physical variables could be shaping their community structure and function. Ten Precambrian Shield lakes in the Muskoka-Haliburton region, and ten St Lawrence lowland lakes in the Kawartha lakes region were sampled. These lakes are geologically and chemically distinct, creating natural chemical and physical gradients within and between both regions. Community function was assessed using stable isotope analysis to elucidate carbon transfer dynamics (δ13C) and food web interactions (δ15N). It was predicted that the BMI from Shield lakes would have a δ13C signature indicative of allochthonous carbon subsidies, whereas the lowland lake BMI signatures would reflect autochthonous production. Additionally, it was predicted that the food web length (measured in δ15N units) would be different in Shield and lowland lakes. Both of these predictions were supported; however, the data indicate that δ13C signatures are more likely influenced by catchment geology (represented by bicarbonate concentration) than the extent of allochthony. The best predictor of food web length was found to be region. To assess BMI community structure, taxonomic richness, %EPT (% Ephemeroptera, Plecoptera, Trichoptera; a water quality index), and distribution of functional feeding groups were examined. Based on chemistry it was expected that the Shield lakes would be more speciose, and of greater water quality (relatively lower nutrient levels). These predictions were rejected; since there were no significant regional differences in taxonomic richness or biologically inferred water quality (%EPT). However, sediment size was found to best explain the variability in both metrics, with greater richness and %EPT found at sites with medium and small substrates than those with large substrates. Significant regional differences were found in the distribution of functional feeding groups. Most notably, there were significantly greater proportions of scrapers and shredders in the lowland and Shield lakes, respectively. Based on the feeding mechanisms of these invertebrates it can be inferred that allochthonous subsidies are likely of greater importance to Shield lake BMI communities than those of the lowland lakes; supporting the carbon transfer prediction. These findings provide insight about the structure and function of BMI communities from two dominant lake types in Ontario, and could be useful when determining how future chemical and physical changes will impact these communities. Author Keywords: benthic macroinvertebrates, community function, community structure, Precambrian Shield, stable isotopes, St. Lawrence lowlands
origin and ecological function of an ion inducing anti-predator behaviour in Lithobates tadpoles
Chemical cues are used commonly by prey to identify predation risk in aquatic environments. Previous work has indicated that negatively-charged ions of m/z 501 are possibly a kairomone that induces anti-predator responses in tadpoles. This thesis found that this ion species: (i) is produced by injured tadpoles; (ii) exhibits increased spectral intensity with higher tadpole biomass; and (iii) is not produced by starved predators. These results refute the hypothesis that the ion is a kairomone, and rather support its role as an alarm cue released from tadpoles. High resolution mass spectrometry (HR-MS) revealed a unique elemental composition for [M-H]-, m/z 501.2886, of C26H45O7S-. Collision induced dissociation (CID) of ion m/z 501 formed product ions of m/z 97 and m/z 80, HSO4- and SO3-, respectively, indicating the presence of sulfate. Green frog (Lithobates clamitans) tadpoles exposed to m/z 501, and an industrial analogue, sodium dodecyl sulphate (NaC12H25O4S), exhibited similar anti-predator responses, thereby suggesting the potential role of organic sulfate as a tadpole behavioural alterant. Author Keywords: Alarm cue, Amphibian, Chemical Ecology, Mass spectrometry, Predator-prey interactions
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
multi-faceted approach to evaluating the detection probability of an elusive snake (Sistrurus catenatus)
Many rare and elusive species have low detection probabilities, thereby imposing unique challenges to monitoring and conservation. Here, we assess the detection probability of the Eastern Massasauga (Sistrurus catenatus) in contrast to a more common and conspicuous species, the Eastern Gartersnake (Thamnophis sirtalis). We found that patterns of detection probability differed between species, wherein S. catenatus was detected less often and under a more specific set of sampling conditions. Correspondingly, detection trials with S. catenatus found a high non-detection rate, while detection trials with artificial models suggest that regional differences in detection probability are driven by variation in population density and habitat use. Our results suggest that current monitoring efforts are not sufficient, and that S. catenatus is frequently undetected. Accordingly, we highlight the importance of species-specific monitoring protocols when monitoring rare and elusive species, and recommend a multi-faceted approach that estimates detection probability and identifies species-specific challenges to monitoring. Author Keywords: detection probability, elusive species, monitoring programs, non-detection, S. catenatus, snakes
methodological framework for the assessment and monitoring of forest degradation under the REDD+ programme based on remote sensing techniques and field data
In this thesis, a methodological framework for the assessment and monitoring of forest degradation based on remote sensing techniques and field data, as part of the REDD+ programme, is presented. The framework intends to support the implementation of a national Monitoring, Verification and Report (MRV) system in developing countries. The framework proposed an operational definition of forest degradation and a set of indicators, namely Canopy Cover (CC), Aboveground Biomass (AGB) and Net Primary Productivity (NPP), derived from remote sensing data. The applicability of the framework is tested in a sub-deciduous tropical forest in the Southeast of Mexico. The results from the application of the methodological framework showed that the higher rates of forest degradation, 1596-2865 ha·year-1, occur in areas with high population density. Estimations of aboveground biomass in these degraded areas span from 1 to 24 Mg·ha-1, with a rate of carbon fixation ranging from 130 to 246 gC·m2·year. The results also showed that 43 % of the forests of the study area remain with no evident signs of degradation, as detected by the indicators selected, during the period evaluated. The integration of the different elements conforming the methodological framework for the assessment and monitoring of forest degradation enabled the identification of areas that maintain a stable condition and areas that change over the period evaluated. The methodology outlined in this thesis also allows for the identification of the temporal and spatial distributions of forest degradation based on the indicators selected, and it is expected to serve as the basis for operations of the REDD+ programme with the appropriate adaptations to the area in turn. Author Keywords: Forest degradation, Monitoring, REDD+, Remote Sensing, Tropical forest
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
maskihkîyâtayôhkêwina; mashkikiiwaadizookewin
maskihkîyâtayôhkêwina- mashkikiiwaadizookewin: Cree and Anishnaabe Narrative Medicine in the Renewal of Ancestral Literature Jud Sojourn This work represents an experiment in developing Cree and Anishnaabe nation-specific approaches to understanding Cree and Anishnaabe texts. The binding premise that guides this work has to do with narrative medicine, the concept that narrative arts, whether ancestral storytelling or current poetry have medicine, or the ability to heal and empower individuals and communities. As âtayôhkêwin in Cree and aadizookewin in Anishnaabemowin refer to ancestral traditional narratives, and while maskihkiy in Cree, and mashkiki in Anishnaabemowin refer to medicine, maskihkîyâtayôhkêwina and mashkikiiwaadizookewin mean simply `narrative medicine' in Cree and Anishnaabemowin respectively. After establishing a formative sense for what narrative medicine is, this work continues by looking at the bilingual Ojibwa Texts (1917, 1919) transcribed by William Jones in 1903-1905 on the north shore of Lake Superior and in northern Minnesota Anishnaabe communities, those spoken by Anishnaabe community members Gaagigebinesiikwe, Gaagigebinesii, Midaasookanzh, Maajiigaaboo, and Waasaagooneshkang. Then focus then turns to the bilingual Plains Cree Texts (1934) transcribed by Leonard Bloomfield at the Sweet Grass Reserve in Saskatchewan and spoken by Cree community members nâhnamiskwêkâpaw, sâkêwêw, cicikwayaw, kâ-kîsikaw pîhtokêw , nakwêsis, mimikwâs, and kâ-wîhkaskosahk. The themes that emerge from looking at these texts when combined with an appreciation for the poetics of the Cree and Anishnaabe languages provide the foundation for looking at newer poetry including the work of Cree poet Skydancer Louise Bernice Halfe, centering on the contemporary epic prayer-poem The Crooked Good (2007) and the works of Anishnaabe poet Marie Annharte Baker, focusing on Exercises in Lip Pointing (2003). Each poet emerged as having an understanding her own role in her respective nation as renewing the narrative practices of previous generations. Understandings of the shape or signature of each of the four works' unique kind of narrative medicine come from looking at themes that run throughout. In each of the four works the maskihkîyâtayôhkêwina - mashkikiiwaadizookewin, the narrative medicine they express occurs through or results in mamaandaawiziwin in Anishnaabemowin or mamâhtâwisiwin, in Cree - the embodied experience of expansive relationality. Keywords: Cree, Anishnaabe, nêhiyawêwin, Anishnaabemowin, narrative medicine, traditional stories, poetics, poetry, literary criticism, literary nationalism, Indigenous, indigenist. Author Keywords: Anishnaabe, Anishnaabemowin, Cree, Indigenous, nêhiyawêwin, Poetics
knight and his horse
This thesis examines the social impact of horses on French elites between 1150 and 1300. Using courtly literature, a veterinary treatise, manuscript illuminations, archeological studies, material artefacts, and account books, it explores the place of horses in elite society—practical and symbolic—and assesses the social costs of elite use and ownership of horses. While horses served practical functions for elites, their use and investment in horses clearly went far beyond practicality, since elites used horses recreationally and sought prestigious horses and highly decorated equipment. Their owners used horses in displays of power, status, and wealth, as well as in displays of conspicuous consumption and the performance of gender roles. The social display associated with horses was integrally tied to the ideology and performance of chivalry. This study examines the broader use of horses by elites to understand their place in the elite culture of the High Middle Ages. Author Keywords: Horses, Knighthood, Medieval France, Military History, Nobility, Social History

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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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