Graduate Theses & Dissertations


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
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 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
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
Understanding Historical and Contemporary Gene Flow Patterns of Ontario Black Bears
Consequences of habitat loss and fragmentation include smaller effective population sizes and decreased genetic diversity, factors that can undermine the long-term viability of large carnivores that were historically continuously distributed. I evaluated the historical and contemporary genetic structure and diversity of American black bears (Ursus americanus) in Ontario, where bear habitat is largely contiguous, except for southern regions that experience strong anthropogenic pressures. My objectives were to understand gene flow patterns in a natural system still largely reflective of pre-European settlement to provide context for the extent of genetic diversity loss in southern populations fragmented by anthropogenic influences. Phylogeographic analyses suggested that Ontario black bears belong to a widespread "continental" genetic group that further divides into 2 subgroups, likely reflecting separate recolonization routes around the Great Lakes following the Last Glacial Maximum. Population genetic analyses based on individual genotypes showed that Ontario black bears are structured into 3 contemporary genetic clusters. Two clusters, located in the Northwest (NW) and Southeast (SE), are geographically vast and genetically diverse. The third cluster is less diverse, and spatially restricted to the Bruce Peninsula (BP). Microsatellite analyses revealed that the NW and SE clusters are weakly differentiated from each other relative to mitochondrial DNA findings, suggesting male-biased dispersal and isolation by distance across the province. I also conducted simulations to assess competing hypotheses that could explain the reduced genetic diversity on the BP, which supported a combination of low migration and recent demographic bottlenecks. I showed that management actions to increase genetic variation in BP black bears could include restoring landscape connectivity between BP and SE; however, the irreversible human footprint in the area makes regular translocations from SE individuals a more practical alternative. Overall, my work suggests that: 1) historical genetic processes in Ontario black bears were likely predominated by isolation by distance, 2) large mammalian carnivores such as black bears can become isolated and experience reduced diversity in only a few generations, and 3) maintaining connectivity in regions under increased anthropogenic pressures could prevent populations from becoming small and geographically and genetically isolated, and should be a priority for conserving healthy populations. Author Keywords: American black bear, carnivore, conservation genetics, Ontario, phylogeography, population genetics
Time to adapt
To better understand species’ resilience to climate change and implement solutions, we must conserve environments that maintain standing adaptive genetic variation and the potential generation of new beneficial alleles. Coding trinucleotide repeats (cTNRs) providing high-pace adaptive capabilities via high rates of mutation are ideal targets for mitigating the decline of species at risk by characterizing adaptively significant populations. Ultimately, adaptive genetic information will inform the protection of biological diversity below the species level (i.e., “Evolutionarily Significant Units” or “ESUs”). This dissertation investigates cTNRs within candidate genes to determine their prevalence and influence under selection in North American mammals. First, I evaluated the potential for somatic mosaicism in Canada lynx (Lynx canadensis), and found that tissue-specific mosaicism does not confound cTNR genotyping success in lynx. Second, I assessed a selection of clock gene cTNRs across characterized mammals and found that these repeats are abundant and highly variable in length and purity. I also identified preliminary signatures of selection in 3 clock gene cTNRs in 3 pairs of congeneric North American mammal species, highlighting the importance of cTNRs for understanding the evolution and adaptation of wild populations. I further evaluated the influence of selection on the NR1D1 cTNR within Canada lynx sampled across Canada using environmental correlation, where I estimated the variation in NR1D1 cTNR alleles explained by environmental and spatial variables after removing the effects of neutral population structure. Although most variation was explained by neutral structure, environment and spatial patterns in eastern lynx populations significantly explained some of the variation in NR1D1 alleles. To examine the role of island populations in the generation and distribution of adaptive genetic variation, I used 14 neutral microsatellites and a dinucleotide repeat within a gene linked to mammalian body size, IGF-1, and found that both genetic drift and natural selection influence the observed genetic diversity of insular lynx. Finally, I estimated the divergence dates of peripheral lynx populations and made recommendations towards the conservation of Canada lynx; high levels of genetic differentiation coupled with post-glacial colonization histories and patterns of divergence at cTNR loci suggest at least 4 ESUs for Canada lynx across their range. Author Keywords: adaptation, Canada lynx, candidate genes, coding trinucleotide repeats, evolution, natural selection
Stress Axis Function and Regulation in New World Flying Squirrels
Across vertebrate taxa, the hypothalamic-pituitary-adrenal axis (or the stress axis) is highly conserved, and is central to vertebrate survival because it allows appropriate responses to psychological stressors. Habitat shapes successful physiological and ecological strategies, and to appreciate how individual species respond to stressors in their environment, it is essential to have a thorough knowledge of the basic stress physiology of each species. In this dissertation, I studied the functioning and evolution of the stress physiology of New World flying squirrels. I showed that baseline, circulating cortisol levels in northern (Glaucomys sabrinus) and southern (G. volans) flying squirrels are some of the highest ever reported for mammals, indicating that their stress axes operate at a higher set point than most other species. I also assessed other aspects of their acute stress response, including free fatty acid and blood glucose levels, and indices of immune function, and showed that the flying squirrels’ physiological reaction to stressors may differ from that of other mammals. Using immunoblotting, I found that corticosteroid-binding globulin (CBG) expression levels in flying squirrels appeared to be higher than previously reported using alternative methods. I also concluded however, that these levels did not appear to be high enough to provide their tissues with the protective CBG-bound buffer from their high circulating cortisol concentrations experienced by the majority of vertebrates. Thus, this arm of cortisol regulation within the flying squirrel stress axes may be weak or non-existent. Following this, I focused on southern flying squirrels and showed evidence that the second arm of cortisol regulation — the negative feedback mechanism at the level of the brain — functions effectively, but that this species is glucocorticoid resistant. Their tissue receptors appear to have a reduced affinity for cortisol, and this affinity may change seasonally to allow for the onset of other biological processes required for survival and reproduction. Due to their distinctive stress physiology, northern and southern flying squirrels may provide comparative physiologists with model systems for further probing of the function and evolution of the stress axis among vertebrates. Author Keywords: corticosteroid-binding globulin, flying squirrel, Glaucomys, glucocorticoids, physiological ecology, stress physiology
Size and fluorescence properties of allochthonous dissolved organic matter
Dissolved organic matter (DOM) is a mixture of molecules with dynamic structure and composition that are ubiquitous in aquatic systems. DOM has several important functions in both natural and engineered systems, such as supporting microorganisms, governing the toxicity of metals and other pollutants, and controlling the fate of dissolved carbon. The structure and composition of DOM determine its reactivity, and hence its effectiveness in these ecosystem functions. While the structure, composition, and reactivity of riverine and marine DOM have been previously investigated, those of allochthonous DOM collected prior to exposure to microbes and sunlight have received scant attention. The following dissertation constitutes the first in-depth study of the structure, composition, and reactivity of allochthonous DOM at its point of origin (i.e. leaf leachates, LLDOM), as detected by measuring its size and optical properties. Concomitantly, novel chemometric methods were developed to interpret size-resolved data obtained using asymmetrical flow field-flow fractionation, including spectral deconvolution and the application of machine learning algorithms such as self-organizing maps to fluorescence data using a dataset of more than 1000 fluorescence excitation-emission matrices. The size and fluorescence properties of LLDOM are highly distinct. Indeed, LLDOM was correctly classified as one of 13 species/sources with 92.5% accuracy based on its fluorescence composition, and LLDOM was distinguished from riverine DOM sampled from eight different rivers with 98.3% accuracy. Additionally, both fluorescence and size properties were effective conservative tracers of DOC contribution in pH-controlled mixtures of leaf leachates and riverine DOM over two weeks. However, the structure of LLDOM responded differently to pH changes for leaves/needles from different tree species, and for older needles. Structural changes were non-reversible. Copper-binding strength (log K) differed for the different fluorescent components of DOM in a single allochthonous source by more than an order of magnitude (4.73 compared to 6.11). Biotransformation preferentially removed protein/polyphenol-like fluorescence and altered copper-binding parameters: log K increased from 4.7 to 5.5 for one fluorescent component measured by fluorescence quenching, but decreased from 7.2 to 5.8 for the overall DOM, as measured using voltammetry. The complexing capacity of DOM increased in response to biotransformation for both fluorescent and total DOM. The relationship between fluorescence and size properties was consistent for fresh allochthonous DOM, but differed in aged material. Since the size and fluorescence properties of LLDOM are strikingly different from those of riverine DOM, deeper investigation into transformative pathways and mixing processes is required to elucidate the contribution of riparian plant species to DOM signatures in rivers. Author Keywords: Analytical chemistry, Chemometrics, Dissolved organic matter (DOM), Field-flow fractionation, Fluorescence spectroscopy, Parallel factor analysis (PARAFAC)


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