Graduate Theses & Dissertations

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Aquatic Invertebrate Studies from Two Perspectives
Leaf litter decomposition represents a major pathway for nutrient cycling and carbon flow in aquatic ecosystems, and macroinvertebrates play an important role in the processing of this material. To assess the causes of variable leaf breakdown and nutrient fluxes, I measured decomposition rates and the nutrient release ratios of decomposing leaf material across a broad latitudinal gradient in Ontario boreal lakes which varied in nutrients, temperature, and pH. I examined the effects of macroinvertebrates using inclusion and exclusion bags. Generally, leaves decomposed faster in nutrient-rich, warmer lakes. Macroinvertebrates increased decomposition rates but their effects were relatively small compared to regional effects of nutrients and temperature. In addition, we found differential effects of nutrients and temperature on nutrient release ratios, which were partially determined by the release and retention of N and P. These results indicate that changes in these important environmental lake variables could alter decomposition dynamics in Ontario lakes, with implications for nutrient cycling and the storage of this important external carbon source. I studied the biogeography of predaceous diving beetles (Coleoptera: Dytiscidae) in two remote and understudied regions: the Far North of Ontario, and Akimiski Island, Nunavut. I identified 35 species from northern Ontario, including three first provincial records for Ontario, Acilius athabascae Larson (1975), Hygrotus unguicularis (Crotch 1874), and Nebrioporus depressus (Fabricius 1775). I also documented three significant range extensions and six gap-infills for this region. I collected and identified 16 species from Akimiski Island, Nunavut, which include several first time reports for these species for the Nunavut territory. My collections also extend the known ranges of five species into the Hudson Plains Ecozone. This work provides important baseline information on the distribution of diving beetles for these regions. Author Keywords: biodiversity, Boreal Shield, decomposition, Dytiscidae, ecological stoichiometry, macroinvertebrates
Assessing Brook Trout (Salvelinus fontinalis) Seasonal Occupancy in Haliburton County, ON Using Environmental DNA
Brook trout (Salvelinus fontinalis) are declining across Ontario in both numbers and distribution, prompting concern for their future. Here, conventional, emerging, and predictive tools were combined to document brook trout occupation across seasons using streams in Haliburton County, ON as model systems. By using the Ontario Ministry of Natural Resources and Forestry’s (OMNRFs) Aquatic Ecosystem Classification (AEC) system variables with environmental DNA (eDNA) sampling and backpack electrofishing, my research supports the development of species occupancy models (SOMs) and eDNA as tools to document brook trout occurrence. To do this, eDNA sampling was validated in Canadian Shield stream environments by comparison with single-pass backpack electrofishing before seasonally sampling two river systems across their main channel and tributaries to assess occupancy. Streams were classified as potential high, moderate, and low-quality brook trout habitats using indicator variables within the AEC and sampled seasonally with eDNA to quantify occupancy and relate it to habitat potential at the county scale. Results showed eDNA to be an effective tool for monitoring fish across Canadian Shield landscapes and that brook trout occupancy varied seasonally within and across watersheds, suggesting that habitat and fish management strategies need to consider seasonal movement and spatial connectivity. Using these tools will enable biologists to efficiently predict and document brook trout occurrences and habitat use across the landscape. Author Keywords: Aquatic Ecosystem Classification, brook trout, Canadian Shield, connectivity, environmental DNA, seasonal occupation
Assessing Canada Lynx Dispersal Across an Elevation Barrier
Mountain ranges are often thought to restrict movement of wildlife, yet previous studies evaluating the role of the Rocky Mountains as a dispersal barrier for Canada lynx (Lynx canadensis) have been contradictory. Our study uses neutral microsatellite loci to evaluate the role of the Rocky Mountains as a barrier to gene flow for lynx. Although lynx exhibited low genetic differentiation, we detected a limited effect of the mountains. Furthermore, we inferred the role played by landscape variables in gene flow (genetic differentiation predicted by landscape resistance). Limited gene flow most strongly related to resistance from physical factors (low snow cover and elevation), rather than other topographic and ecological factors (high terrain roughness, low forest cover, low habitat suitability, and geographic distance). Structural connectivity was a relatively poor predictor of functional connectivity. Overall, the Rockies represent an area of reasonably high functional connectivity for lynx, with limited resistance to gene flow. Author Keywords: Canada lynx, connectivity, gene flow, genetic structure, landscape genetics, Rocky mountains
Assessing Measured and Perceived Risks to Drinking Water Sources
Microcontaminants originating from wastewater effluent and run-off from agricultural lands may be present in the sources of drinking water for rural and Indigenous communities in mixed-use watersheds. In this study, a convergent parallel mixed-methods design was applied to assess measured and perceived risks of contamination in the sources of drinking water for two communities; the Six Nations of the Grand River community in Ontario and the community of Soufriere in St. Lucia, West Indies. The overall goal of the project was to assess how measured and perceived risks of exposure to chemical and biological contaminants in drinking water sources could inform water management strategies for the communities. Quantitative data obtained from the analysis of water samples collected indicated that the highest levels and occurrence of fecal bacteria were found in the Soufriere watershed while the highest concentrations and occurrence of pesticides were found in the Grand River watershed. In the Grand River watershed, conventional treatment of water followed by activated carbon filtration and UV disinfection removed fecal bacteria and also removed many chemical microcontaminants with efficiencies as high as 98%. Data from both watersheds indicated that there was a strong positive correlation between the levels of caffeine and sucralose (i.e. indicators of wastewater contamination) in water samples and the levels of either Total Coliforms or fecal bacteria of human origin. Human health risk assessments of individual pesticides and pesticide mixtures performed by applying a hazard quotient (HQ) and hazard index (HI) model, respectively indicated that there were no apparent risks to human health from those microcontaminants. Qualitative data obtained from face-to-face interviews with water managers and health professionals working in the two communities, which were collected and analysed concurrently but independently, illustrated that there were cross-cultural similarities and differences in factors influencing the perceptions of risks associated with the sources of drinking water. These perceptions of risks were mainly influenced by factors such as heuristics or informal and informal reasoning, cognitive-affective factors, social-political institutions and cultural factors. These factors may have also influenced water managers and health professionals, as they often recommended more “soft” strategies for managing water resources in the communities. Key words: pesticides, fecal bacteria, microcontaminants, POCIS, measured risks, perceived risks, water management, First Nations, Grand River, Soufriere, St. Lucia Author Keywords: fecal bacteria, measured risks, microcontaminants, perceived risks, POCIS, water management
Assessing basin storage
Water storage is a fundamental component of drainage basins, controlling the synchronization between precipitation input and streamflow output. The ability of a drainage basin to store water and regulate streamflow may mediate sensitivity to climate and land cover change. There is currently no agreement on the best way to quantify basin storage. This study compares results of a combined hydrometric and isotopic approach for characterizing inter-basin differences in storage across the Oak Ridges Moraine (ORM) in southern Ontario. The ratio of the standard deviation of the stable isotope signature of streamflow relative to that of precipitation has been shown to be inversely proportional to mean water transit times, with smaller ratios indicating longer water transit times and implying greater storage. Stable isotope standard deviation ratios were inversely related to baseflow index values. Basins demonstrating longer transit times were associated with hydrological characteristics that promote infiltration and recharge of storage. Author Keywords: baseflow, basin storage, climate change, mean transit time, Oak Ridges Moraine, stable isotopes
Assessing effects and fate of environmental contaminants in invasive, native, and endangered macrophytes
Macrophytes play an important role in aquatic ecosystems, and thus are integral to ecological risk assessments of environmental contaminants. In this dissertation, I address gaps in the assessments of contaminant fate and effects in macrophytes, with focus on glyphosate herbicide use for invasive plant control. First, I evaluated the suitability of Typha as future standard test species to represent emergent macrophytes in risk assessments. I concluded that Typha is ecologically relevant, straight-forward to grow, and its sensitivity can be assessed with various morphological and physiological endpoints. Second, I assessed effects from glyphosate (Roundup WeatherMAX® formulation) spray drift exposure on emergent non-target macrophytes. I performed toxicity tests with five taxa, Phragmites australis, Typha × glauca, Typha latifolia, Ammannia robusta, and Sida hermaphrodita, which in Canada collectively represent invasive, native, and endangered species. I found significant differences in glyphosate sensitivity among genera, and all species’ growth was adversely affected at concentrations as low as 0.1% (0.54 g/L), much below the currently used rate (5%, 27 g/L). Third, I assessed the potential for glyphosate accumulation in and release from treated plant tissues. I found that P. australis and T. × glauca accumulate glyphosate following spray treatment, and that accumulated glyphosate can leach out of treated plant tissues upon their submergence in water. Finally, I assessed effects of released glyphosate on non-target macrophytes. I found that P. australis and T. × glauca leachate containing glyphosate residues can stimulate the germination and seedling growth of T. latifolia, but can exert an inhibiting effect on A. robusta, although leachate without glyphosate caused similar responses in both plants. Additionally, I found no negative effects in A. robusta when exposed to glyphosate residues in surface water, or when grown with rhizosphere contact to an invasive plant that was wicked (touched) with glyphosate. My results show that non-target macrophytes can be at risk from glyphosate spray for invasive plant control, but risks can be mitigated through informed ecosystem management activities, such as targeted wick-applications or removing plant litter. Integrating contaminant fate and effect assessments with emergent macrophytes into ecological risk assessments can support the protection of diverse macrophyte communities. Author Keywords: Ecosystem management, Ecotoxicology, Glyphosate, Herbicide, Invasive plant, Species at risk
Assessing habitat suitability and connectivity for an endangered salamander complex
Habitat loss and fragmentation have significantly contributed to amphibian population declines, globally. Evaluating the state of remaining habitat patches can prove to be beneficial in identifying areas to prioritize in conservation efforts. Pelee Island, Ontario is home to a complex of salamanders including small-mouthed salamanders (Ambystoma texanum), blue-spotted salamanders (A. laterale) and unisexual Ambystoma (small-mouthed salamander dependent population). These populations have declined from intense landscape changes since the late 1800s, particularly from the historical drainage of wetlands. In this thesis, I evaluated the suitability and connectivity of habitat patches occupied by these salamanders to assess the size of, and dispersal capabilities between, remaining habitat patches. I found that there was a low amount of suitable terrestrial habitat available for this complex of salamanders, and existing habitat patches were small and isolated. Forested areas and non-breeding wetlands were considered to be suitable habitat when adjacent to existing breeding locations, suggesting that these habitats should be a focus for conservation efforts. Notably, intervention may be necessary to maintain this amphibian complex as many assemblages are isolated from one another and potential corridors currently consist of primarily unsuitable habitat. Given that much of the salamander complex is reliant on one species for reproduction, the long-term viability of this population of Ambystoma salamanders may rely on the enhancement of suitable habitat near current breeding sites by conservation organizations and local stakeholders. Ultimately, the approach used in this thesis emphasizes the value of evaluating habitat within a fragmented landscape to focus conservation efforts on imperilled species. Author Keywords: amphibians, connectivity, habitat suitability, landscape fragmentation, landscape resistance, unisexual
Assessing limnological characteristics of subarctic Québec thaw ponds and mercury methylation and methylmercury demethylation within their sediments
Thawing permafrost due to increasingly warm temperatures in northern subarctic regions is releasing mercury. The consequent formation of thaw ponds in the peatland palsa valley of the Sasapimakwananisikw (SAS) river in Whapmagoostui-Kuujjuarapik, Québec may provide a pool for MMHg formation and a potential risk to aquatic and human life, if these ponds facilitate MMHg export through hydrological connections to nearby waterways. Hg methylation and MMHg demethylation activities were examined in thaw pond sediments using a Hg tracer isotope incubation experiment. Analysis by coupling gas chromatography cold-vapor atomic fluorescence spectrophotometry (GC-CVAFS) with inductively coupled mass spectrometry (ICP-MS) techniques showed that MMHg was produced at a higher rate and within the first 2 h of incubation for both summer and winter seasons. For thaw ponds SAS1A, SAS1B and SAS2A, MMHg was formed at 0.0048 % h-1, 0.0012 % h-1, and 0.0008 % h-1, respectively during winter and at 0.0001 % h-1, 0.0016 % h-1, and 0.0010 % h-1, respectively during summer. Detection of MMHg losses were not as expected likely due to limitations of the combined tracer spike and overestimation of the in situ ambient mercury levels. Physical and chemical properties vary within ponds, among ponds and between winter and summer. SAS1B’s location nearby an organic carbon rich palsa may be ideal to study DOC – Hg interactions. Variability in pond characteristics including depth, surface area, age, pH, temperature, colour, oxygen concentration, total dissolved and suspended solids, conductivity, carbon, mercury, ammonium, calcium, magnesium, sulfate, total phosphorous, potassium, and sodium between seasons indicate the challenge of predicting future environmental impacts of climate change related thaw pond creation in the north. Author Keywords: demethylation, mercury, methylation, methylmercury, SAS, thaw ponds
Assessing the Potential for Contamination of Lakes from Upwelling of Arsenic-Laden Groundwater Through Sediments
A bedrock fracture hosting arsenic (As) contaminated groundwater was suspected to be transported to Ramsey Lake, a drinking water resource for more than 50,000 residents of Sudbury, Ontario. A high resolution, spatial, water quality mapping technique using an underwater towed vehicle (UTV) was used to identify sources of upwelling groundwater into lake water and localize the upwelling As contaminated groundwater vent site. The top 7 cm of lake sediments (in-situ) at this vent site were observed to adsorb 93 % of the dissolved As, thus inhibiting lake water quality degradation from this contaminant source. Sediment samples from this location were used in laboratory experiments to assess the potential for this system to become a source of As contamination to Ramsey Lake water quality and elucidate As(III) fractionation, transformation and redistribution rates and processes during aging. Arsenic speciation is important because As(III) has been shown to be more toxic than As(V). To accomplish this a sequential extraction procedure (SEP) that maintains As(III) and As(V) speciation in (sub)oxic sediments and soils was validated for the operationally defined fractions: easily exchangeable, strongly sorbed, amorphous Fe oxide bound, crystalline Fe oxide bound, and the residual fraction for total As because the characteristics of the reagents required to extract the final fraction do not maintain As species. Batch reaction experiments using sediment spiked with As(III) or As(V) and aged for up to 32 d were sequentially extracted and analysed for As(III) and As(V). Consecutive reaction models illustrate As(III) is first adsorbed to the sediment then oxidized to As(V). Fractionation analyses show As(III) most rapidly adsorbs to the easily exchangeable fraction where it is oxidized and redistributes to the strongly sorbed and amorphous Fe oxide bound fractions. Oxidation of As(III) adsorbed to the amorphous and crystalline Fe oxide bound fractions is less efficient and possibly inhibited. Select samples amended with goethite provide evidence supporting Mn(II) oxidation is catalyzed by the goethite surface, thus increasing As(III) oxidation by Mn(III/IV) complexed with the strongly sorbed fraction. Although As immobilization through groundwater sediment interactions may be inhibited by increased ion activity, particularly phosphate or lake eutrophication, this threat in Ramsey Lake is likely low. Author Keywords: arsenic, fractionation, modelling, redistribution, speciation, water quality mapping
Assessing the Potential of Permaculture as an Adaptation Strategy Towards Climate Change in Central Ontario
This thesis uses three approaches to assess the potential of permaculture in Central Ontario. This was done using a vegetable field trial and modelling programs to determine the effectiveness of permaculture to decrease negative impacts of climate change based on projected climate values derived from regional circulation models. The first approach showed no statistical difference (P<0.05) of applying varied volumes and combinations of organic amendments on crop yields. The second approach indicated permaculture may be a sustainable production system with respect to soil erosion when compared to traditional agricultural practices. The third approach was inconclusive due to the lack of quantitative literature on permaculture management impacts on biomass yields, soil carbon or nutrient retention, which were missing from basic and scientific literature searches. The models used within this thesis include USLE, RUSLE2, AgriSuite, RothC and Holos. Author Keywords: Agriculture, Climate Change, Computer Modelling, Permaculture, Soil Erosion and Assessment
Assessing the environmental correlates of a lethal amphibian pathogen, Batrachochytrium dendrobatidis, in Ontario wetlands
Many emerging infectious diseases are caused by pathogens that possess free-living life stages, in which they interact with the environment directly rather than through the mediation of a host. These diseases represent major impediments to wildlife conservation; however, the dynamics of their interaction with the environment are poorly studied, often due to the difficulty of detecting these microscopic pathogens in environmental samples. One of these pathogens is Batrachochytrium dendrobatidis (Bd), a fungus that has been linked to declines in many amphibian species. In this thesis I use an emerging technique, environmental DNA detection (eDNA), to detect and quantify Bd in the water of southern Ontario (Canada) wetlands and examine its correlation with a variety of aspects of water quality, surrounding habitat, and seasonal timing. My purpose was to inform not only on potential environment-pathogen dynamics for Bd in northern environments, but to provide insight into the use of eDNA as a disease surveillance tool. I found that not only was there high geographic variation in Bd detection and intensity, but also high temporal variation within the same site on time scales as low as two weeks. While Bd prevalence was not strongly correlated with any of the variables tested, intensity showed strong correlation with canopy cover, with greater canopy cover over a waterbody correlating to lower Bd intensity. My results present several promising avenues for further examination of Bd in northern ecosystems, and indicate that, while caution is warranted in its implementation, eDNA may become an important tool in amphibian pathogen surveillance. Author Keywords: amphibian disease, Batrachochytrium dendrobatidis, disease monitoring, environment-pathogen dynamics, environmental DNA, wildlife disease
Assessing the population genetic structure of the endangered Cucumber tree (Magnolia acuminata) in southwestern Ontario using nuclear and chloroplast genetic markers.
Magnolia acuminata (Cucumber tree) is the only native Magnolia in Canada, where it is both federally and provincially listed as endangered.Magnolia acuminata in Canada can be found inhabiting pockets of Carolinian forest within Norfolk and Niagara regions of southwestern Ontario. Using a combination of nuclear and chloroplast markers, this study assessed the genetic diversity and differentiation of M. acuminata in Canada, compared to samples from the core distribution of this species across the United States. Analyses revealed evidence of barriers to dispersal and gene flow among Ontario populations, although genetic diversity remains high and is in fact comparable to levels of diversity estimated across the much broader range of M. acuminata in the USA. When examining temporal differences in genetic diversity, our study found that seedlings were far fewer than mature trees in Ontario, and in one site in particular, diversity was lower in seedlings than that of the adult trees. This study raises concern regarding the future viability of M. acuminata in Ontario, and conservation managers should factor in the need to maintain genetic diversity in young trees for the long-term sustainability of M. acuminata in Ontario. Author Keywords: conservation genetics, cpDNA, forest fragmentation, Magnolia acuminata, microsatellites, population genetic structure

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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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