Graduate Theses & Dissertations

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wind tunnel based investigation of three-dimensional grain scale saltation and boundary-layer stress partitioning using Particle Tracking Velocimetry
Aeolian transport of sand particles is an important geomorphic process that occurs over a significant portion of the earth’s land surface. Wind tunnel simulations have been used for more than 75 years to advance the understanding of this process; however, there are still several principles that lack validation from direct sampling of the sand particles in flight. Neither the three-dimensional dispersion of, nor the momentum carried by particles in flight have been properly measured. This has resulted in the inability to validate numerical particle dispersion models and the key boundary-layer momentum partitioning model that serves as the framework for understanding the air-sand feedback loop. The primary impediment to these measurements being made is a lack of tools suited for the task. To this end, this PhD aims to improve existing particle tracking technology, thus enabling the collection of particle measurements during wind tunnel experiments that would address the aforementioned knowledge gaps. Through the design and implementation of the Expected Particle Area Searching method, a fully automated particle tracking velocimetry system was developed with the capability to measure within ½ grain diameter of the bed surface under steady state transport conditions. This tool was used to collect the first 3-D data set of particle trajectories, from which it was determined that a mere 1/8th of sand transport is stream aligned and 95% is contained within ± 45o of the mean wind direction. Particles travelling at increasing spanwise angles relative to the stream aligned flow were found to exhibit different impact and ejection velocities and angles. The decrease in the number of particles with increasing height in the saltation cloud, very close to the bed is observed to transition from a power to a linear relation, in contrast to previous literature that observed an exponential decay with coarser vertical resolution. The first direct measurements of particle-borne stress were captured over a range of wind velocities and were compared with earlier fluid stress measurements taken using Laser Doppler Anemometry. In support of established saltation theory, impacting particle momentum is found to contribute strongly to particle entrainment under equilibrium conditions. In opposition to established theory, however, particle-borne stress was found to reach a maximum above the surface and does not match the change in air-borne stress with increasing distance from the surface. Near surface splashed particles, measured herein for the first time, appear to play a greater role in stress partitioning than previously thought. This study suggests that research is needed to investigate the role of bed load transport on stress partitioning, to differentiate between airborne trajectory types, and to develop particle tracking tools for field conditions. Author Keywords: Aeolian Transport, Eolian Transport, Particle Tracking Velocimetry, Saltation, Stress Partitioning, Wind Tunnel Simulation
successful invader in expansion
Researchers have shown increasing interest in biological invasions for the associated ecological and economic impacts as well as for the opportunities they offer to study the mechanisms that induce range expansion in novel environments. I investigated the strategies exhibited by invasive species that facilitate range expansion. Invasive populations exhibit shifts in life-history strategy that may enable appropriate responses to novel biotic and abiotic factors encountered during range expansion. The spatio-temporal scales at which these shifts occur are largely unexplored. Furthermore, it is not known whether the observed dynamic shifts represent a consistent biological response of a given species to range shifts, or whether the shifts are affected by the abiotic characteristics of the new systems. I examined the life-history responses of female round gobies Neogobius melanastomus across fine and coarser spatial scales behind the expansion front and investigated whether invasive populations encountering different environmental conditions (Ontario vs France) exhibited similar life-history shifts. In both study systems, I found an increase in reproductive investment at invasion fronts compared to longer established areas at coarse and fine scales. The results suggest a similar response to range shifts, or a common invasion strategy independent of environmental conditions experienced, and highlight the dynamic nature of an invasive population’s life history behind the invasion front. The second part of my research focused on the development of an appropriate eDNA method for detecting invasive species at early stages of invasion to enable early detection and rapid management response. I developed a simple, inexpensive device for collecting water samples at selected depths for eDNA analysis, including near the substrate where eDNA concentration of benthic species is likely elevated. I also developed a protocol to optimise DNA extraction from water samples that contain elevated concentration of inhibiters, in particular near-bottom samples. Paired testing of eDNA and conventional surveys was used to monitor round goby expansion along its invasion pathway. Round gobies were detected in more sites with eDNA, permitting earlier, more accurate, upstream detection of the expansion front. My study demonstrated the accuracy and the power of using eDNA survey method to locate invasion fronts. Author Keywords: Age-specific reproductive investment, DNA extraction, Energy allocation, Fecundity, Invasion front, Range expansion
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
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
effects of particulate matter on the fate and toxicity of silver nanoparticles
As an emerging contaminant, the antimicrobial agent silver nanoparticles (AgNPs) have been receiving considerable attention to determine their potential effects to aquatic ecosystems. However, estimates of aquatic consumer survivorship and other toxicological endpoints vary considerably among experiments, largely due to the environment in which the test takes place. Throughout this thesis I aim to understand which natural environmental variables impact toxicity to the common aquatic consumer Daphnia. I focus on the effects of particulate matter as it may play a role in animal nutrition as well as interact with AgNPs. I explore particulate matter’s effect on survival in the complex matrices including other natural variables that could impact toxicity. I conduct a series of complimentary field and laboratory studies to understand how particles impact AgNP toxicity and how those interactions vary within whole lake ecosystems. Using laboratory studies, I establish that algal particles mitigate the toxic effects of AgNPs on Daphnia survival through removing Ag from the water column and that phosphorus increases this effect. Using wild Daphnia and lake water, I demonstrate the ability of particulate matter to mitigate toxicity in complex natural settings. It was also one of the major predictors of AgNP toxicity to Daphnia along with dissolved organic carbon and daphnid seasonal health. Finally, using a whole lake AgNP addition experiment, I demonstrate that particles and AgNPs interact variably in the lake. Silver from AgNPs binds to particles and is removed to the sediments through the actions of settling particles without impacting the dynamics of living communities. Overall, I am able to demonstrate that the natural components of lake ecosystems, especially particulate matter, are able to mitigate the effects of AgNPs in lake ecosystems to a point where they likely will be never pose a threat to the survivorship of aquatic consumers such as Daphnia. Author Keywords: Daphnia, ecotoxicity, particulate matter, Silver nanoparticles, whole lake experiment
effects of parasitism on consumer-driven nutrient recycling
Daphnia are keystone consumers in many pelagic ecosystems because of their central role in nutrient cycling. Daphnia are also frequently infected, and the parasites causing these infections may rival their hosts in their ability to regulate ecosystem processes. Therefore, parasitic exploitation of Daphnia may alter nutrient cycling in pelagic systems. This thesis integrates existing knowledge regarding the exploitation of Daphnia magna by 2 endoparasites to predict parasite-induced changes in the nutrient cycling of infected hosts and ecosystems. In chapter 1, I I contextualizing the integration of these themes by reviewing the development of the fields of elemental stoichiometry and parasitology. In chapter 2, we show how the bacterial parasite, Pasteuria ramosa, increased the nitrogen (N) and phosphorus (P) release rates of D. magna fed P-poor diets. We used a mass-balance nutrient release model to show that parasite-induced changes in host nutrient accumulation rates and diet-specific changes in host ingestion rates were responsible for the accelerated nutrient release rates that we observed. In chapter 3, we extended our examination of the nutrient mass balance of infected D. magna to include another parasite, the microsporidian H. tvaerminnensis. We found differences in the effects of these two parasites on host nutrient use as well as support for the hypothesis that parasite-induced changes in Daphnia N release are caused by the effects of infection on Daphnia fecundity. In chapter 4, we examined the relationship between P concentrations and the presence and prevalence of H. tvaerminnensis in rock pools along the Baltic Sea. We found that particulate P concentrations were negatively associated with the prevalence of this parasite, a result that is consistent with the increase in P sequestration of H. tvaerminnensis-infected Daphnia that we observed in chapter 3. I discuss the potential implications of the work presented in chapters 2-4 for other parasite-host systems and ecosystems in chapter 5. Overall, the research presented here suggests that parasite-induced changes in host nutrient use may affect the availability of nutrients in the surrounding environment, and the magnitude of this effect may be linked to parasite-induced reductions in fecundity for many invertebrate hosts. Author Keywords: consumer, ingestion rates, mass-balance, nutrient-recycling, parasitism, phosphorus
effects of heat dissipation capacity on avian physiology and behaviour
In endotherms, physiological functioning is optimized within a narrow range of tissue temperatures, meaning that the capacity to dissipate body heat is an important parameter for thermoregulation and organismal performance. Yet, experimental research has found mixed support for the importance of heat dissipation capacity as a constraint on reproductive performance. To investigate the effects of heat dissipation capacity on organismal performance, I experimentally manipulated heat dissipation capacity in free-living tree swallows, Tachycineta bicolor, by trimming feathers overlying the brood patch, and monitored parental provisioning performance, body temperature, and offspring growth. I found that individuals with an enhanced capacity to dissipate body heat (i.e., trimmed treatment) provisioned their offspring more frequently, and reared larger offspring that fledged more consistently. Although control birds typically reduced their nestling provisioning rate at the highest ambient temperatures to avoid overheating, at times they became hyperthermic. Additionally, I examined inter-individual variation in body temperature within each treatment, and discovered that body temperature is variable among all individuals. This variability is also consistent over time (i.e., is repeatable), irrespective of treatment. Further, I found that individuals consistently differed in how they adjusted their body temperature across ambient temperature, demonstrating that body temperature is a flexible and repeatable physiological trait. Finally, I used a bacterial endotoxin (lipopolysaccharide) to examine the regulation of body temperature of captive zebra finches (Taeniopygia guttata) during an immune challenge. Exposure to lipopolysaccharide induces sickness behaviours, and results in a fever, hypothermia, or a combination of the two, depending on species and dosage. I asked what the relative role of different regions of the body (bill, eye region, and leg) is in heat dissipation/retention during the sickness-induced body temperature response. I found that immune-challenged individuals modulated their subcutaneous temperature primarily through alterations in peripheral blood flow, particularly in the legs and feet, detectable as a drop in surface temperature. These results demonstrate that the importance of regional differences in regulating body temperature in different contexts. Taken together, my thesis demonstrates that heat dissipation capacity can affect performance and reproductive success in birds. Author Keywords: body temperature, heat dissipation, tree swallow, zebra finch
effects of Dissolved Organic Matter (DOM) sources on Pb2+, Zn2+ and Cd2+ binding
Metal binding to dissolved organic matter (DOM) determines metal speciation and strongly influences potential toxicity. The understanding of this process, however, is challenged by DOM source variation, which is not always considered by most existing metal speciation models. Source determines the molecular structure of DOM, including metal binding functional groups. This study has experimentally showed that the allochthonous-dominant DOM (i.e. more aromatic and humic) consistently has higher level of Pb binding than the autochthonous-dominant DOM (i.e. more aliphatic and proteinaceous) by more than two orders of magnitude. This source-discrimination, however, is less noticeable for Zn and Cd, although variation still exceeds a factor of four for both metals. The results indicate that metal binding is source-dependent, but the dependency is metal-specific. Accordingly, metal speciation models, such as the Windermere Humic Aqueous Model (WHAM), needs to consider DOM source variations. The WHAM input of active fraction of DOM participating in metal binding (f) is sensitive to DOM source. The commonly-used f = 0.65 substantially overestimated the Pb and Zn binding to autochthonous-dominant DOM, indicating f needs to be adjusted specifically. The optimal f value (fopt) linearly correlates with optical indexes, showing a potential to estimate fopt using simple absorbance and/or fluorescence measurements. Other DOM properties not optically-characterized may be also important to determine fopt, such as thiol, which shows strong affinity to most toxic metals and whose concentrations are appreciably high in natural waters (< 0.1 to 400 nmol L-1). Other analytical techniques rather than Cathodic Stripping Voltammetry (CSV) are required to accurately quantify thiol concentration for DOM with concentration > 1 mg L-1. To better explain the DOM-source effects, the conditional affinity spectrum (CAS) was calculated using a Fully Optimized ContinUous Spectrum (FOCUS) method. This method not only provides satisfactory goodness-of-fit, but also unique CAS solution. The allochthonous-dominant DOM consistently shows higher Pb affinity than autochthonous-dominant DOM. This source-discrimination is not clearly observed for Zn and Cd. Neither the variability of affinity nor capacity can be fully explained by the variability of individual DOM properties, indicating multiple properties may involve simultaneously. Together, the results help improve WHAM prediction of metal speciation, and consequently, benefit geochemical modelling of metal speciation, such as Biotic Ligand Model for predicting metal toxicity. Author Keywords: Dissolved organic matter, Metal binding, Source, Windermere Humic Aqueous Model
collaborative ecotoxicological risk assessment of in-place pollutants in Owen Sound Bay, Lake Huron within the Saugeen Ojibway Nation Territory
Owen Sound Bay, which is located within the traditional territory of the Saugeen Ojibway Nation (SON), is contaminated as a result of historical industrial and shipping activity. Gross contamination of the sediments in the inner part of the Bay (i.e., Owen Sound Harbour) includes high concentrations of polycyclic aromatic hydrocarbons (PAHs) and other organic compounds, as well as metals that may pose a risk to the SON fishery for lake whitefish (Coregonus clupeaformis). However, evaluating the environmental risks posed by contaminated sediments is a challenge, as these risks are dependent upon several factors and require multiple lines of evidence. Including Indigenous communities in environmental risk assessment and the management of those risks is vital for sustaining ecosystem integrity, as well as respecting Treaty Rights. In this study, a risk assessment framework was developed that included several risk assessment tools used in Western science and also encompassed the concerns and values of the SON, including the application of SON-ecological knowledge. Methods for risk evaluation included gathering lines of evidence though community workshops, as well as field sampling in the Bay to determine the concentrations of PAHs and other organic contaminants in sediments and in the water column. Laboratory studies of toxicity to early life stages of lake whitefish and Japanese medaka (Oryzias latipes) and sediment disturbance simulations to evaluate biological responses in juvenile lake whitefish were also completed as lines of evidence. The results indicate that leaving the harbour “as is” without a thorough analysis of remediation options fails to address the concerns of the people within the SON communities. Overall, this research demonstrated a successful process for developing a collaborative risk assessment framework that recognizes the sovereignty of Indigenous peoples and promotes Nation-to-Nation decision making. Author Keywords: biomarkers, Coregonus clupeaformis, Indigenous knowledge, polycyclic aromatic hydrocarbons, risk assessment, source tracking
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
White-Tailed Fear
The primary method used to maintain white-tailed deer (Odocoileus virginianus) populations at densities that are ecologically, economically, socially, and culturally sustainable is hunter harvest. This method considers only the removal of animals from the population (the direct effect) and does not conventionally consider the costs imposed on deer as they adopt hunter avoidance strategies (the risk effect). The impact of risk effects on prey can exceed that of direct effects and there is interest in applying this concept to wildlife management. Deer are potential candidates as they have demonstrated behavioural responses to hunters. I explored the potential of such a management practice by quantifying how human decisions around hunting create a landscape of fear for deer and how deer alter their space use and behaviour in response. I used a social survey to explore the attitudes of rural landowners in southern and eastern Ontario towards deer and deer hunting to understand why landowners limited hunting on their property. I used GPS tracking devices to quantify habitat selection by hunters and hunting dogs (Canis familiaris) to better understand the distribution of hunting effort across the landscape. I used GPS collars to quantify the habitat selection of deer as they responded to this hunting pressure. I used trail cameras to quantify a fine-scale behavioural response, vigilance, by deer in areas with and without hunting. Human actions created a highly heterogeneous landscape of fear for deer. Landowner decisions excluded hunters from over half of the rural and exurban landscape in southern and eastern Ontario, a pattern predicted by landowner hunting participation and not landcover composition. Hunter decisions on whether to hunt with or without dogs resulted in dramatically different distributions of hunting effort across the landscape. Deer showed a high degree of behavioural plasticity and, rather than adopting uniform hunter avoidance strategies, tailored their response to the local conditions. The incorporation of risk effects into white-tailed deer management is feasible and could be done by capitalizing on a better understanding of deer behaviour to improve current management practices or by designing targeted hunting practices to elicit a landscape of fear with specific management objectives. Author Keywords: Brownian bridge movement models, hunting, landscape of fear, resource utilization functions, risk effects, white-tailed deer
Using ultra high-resolution mass spectrometry to characterize the biosorbent Euglena gracilis and its application to dysprosium biosorption
Euglena gracilis is an enigmatic and adaptable organism that has great bioremediationpotential and is best known for its metabolic flexibility. The research done in this dissertation addresses (1) how growth conditions impact cellular composition, and (2) how chemometric approaches (such as statistical design of experiments and artificial neural networks) are viable alternatives to the conventional biosorption models for process optimization. Using high-resolution mass spectrometry for biosorbent characterization is a powerful way to assess the chemical characteristics of lyophilized and fractionated cells with high precision, especially to screen for compound classes that may have potentiality for rare earth element removal. Growth conditions impacted cellular composition and separated size fractions of cells yielded different molecular/chemical properties as described by compositional abundances, thus different biosorptive potential. Untargeted analysis demonstrated that exponential dark-grown cells with glucose supplementation were abundant in polyphenolic- and carbohydrate-like compounds, molecular species highly involved in rare earth element binding. Light grown cells had more heterogeneity and the highest molecular weighted fractions from light grown cells (fraction D) had the most abundances of polyphenolic- and protein-like structures. Chemometric modeling used identified the best and worst conditions for iii dysprosium sorption and showed that pH had the most significant influence on bioremoval. Bioremoval ranged from 37% at pH 8 to 91% at pH 3 at Dy concentration ranging from 1 to 100 μg L-1. The work presented in the PhD dissertation will aid in understanding the chemical characteristics of biosorbents by using a Van krevelen analysis of elemental ratios whether algal cells are grown in different environmental growth conditions, or when algal cell are size fractionated. This is especially applied for the screening for metal binding potentiality to Dysprosium. Chemometric methods provide an alternative method for the investigating factors for bioremoval, and applications for process optimization and for real-world applications. This dissertation will aid in understanding chemical characteristics when a biosorbent is grown in a given condition and which factors are important for rare earth element (REE) bioremoval. The significance of this work aims to look for alternate ways to screen biosorbents and using a more efficient experimental design for REE bioremoval. Author Keywords: bioremoval, biosorption, chemometrics, dysprosium, euglena, mass spectrometry

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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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