Graduate Theses & Dissertations

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Phosphorus deposition in forested watersheds
Phosphorus (P) is an essential macronutrient. In south-central Ontario, foliar P concentrations are low and studies have suggested that P may be limiting forest productivity. Current catchment mass balance estimates however, indicate that P is being retained suggesting that P should not be limiting to tree growth. Phosphorus deposition is measured using bulk deposition collectors, which are continuously open and therefore are subject to contamination by pollen and other biotic material with high P and potassium (K) concentrations and may therefore overestimate net P inputs to forested catchments. Average annual TP and K deposition at three long-term (1984 – 2013) monitoring sites near Dorset, Ontario ranged from 15 to 20 mg·m-2y-1 and 63 to 85 mg·m-2y-1, respectively, and was higher at Paint Lake compared with Plastic Lake and Heney Lake. Phosphorus and K in bulk precipitation were strongly positively correlated, but deposition patterns varied spatially and temporally among the three sites. Total phosphorus and K deposition increased significantly at Plastic Lake and decreased significantly at Paint Lake, but there was no significant trend in TP or K deposition at Heney Lake over the 30 year period. All sites, but especially Paint Lake, exhibited considerable inter-annual variation in TP and K deposition. To quantify the contribution of pollen, which represents an internal source of atmospheric P deposition, Durham pollen collectors during the spring and summer of 2014 were used. The three sites, Paint Lake, Heney Lake, and Plastic Lake had pollen deposition amounts of 5202 grains·cm-2, 7415 grains·cm-2, and 12 250 grains·cm-2, respectively in 2014. Approximately 83% of pollen deposition can be attributed to white pine and red pine that has a concentration of 3 mg·g-1 of P. It was estimated that pollen alone could account for up to one-third of annual bulk P deposition. Extrapolating winter P deposition values to exclude all potential biotic influences (insects, bird feces, leaves), indicates that bulk deposition estimates may double actual net P to forests, which has implications for long-term P availability, especially in harvested sites. Author Keywords: Atmospheric Deposition, Phosphorus, Pine, Pollen, Potassium, South-Central Ontario
Ground-truthing effective population size estimators using long-term population data from inland salmonid populations
Effective population size (Ne) is a foundational concept in conservation biology, in part due to its relationship to the adaptive potential of populations. Although Ne is often estimated for wild populations, it is rarely calibrated against actual population estimates (Nc) other than to produce Ne/Nc ratios. This project used demographic and genetic data for from two intensively-studied populations of lake trout (Salvelinus namaycush) in Ontario’s Experimental Lake Area (ELA) as baseline data for evaluating the performance of multiple Ne estimators. Several temporal and single-time (point) genetic methods of estimating Ne were compared against demographic Ne estimates and known population data, as well as variation and consistency within and among Ne estimators. Changes in genetic Ne estimates over time were also compared to changes in demographic structure and fluctuating census estimates, including the effect of an experimentally manipulated population bottleneck on demographic and genetic Ne estimates during population reduction and recovery. Sampling years that included the most pre-, during and post-bottleneck data revealed the lowest estimates using temporal estimators (Ne = 16 to 18) despite pre- and post-bottleneck census estimates of 591 and 565. Estimation of Ne had increasingly tighter confidence intervals as sample sizes approached the actual number of breeding individuals in each population. Performance differences among the tested estimators highlight their potential biases and reliance on different assumptions, illustrating their potential value and caveats for assessing adaptive potential of wild populations. Author Keywords: Effective Population Size, Experimental Lakes Area, Fish Population Assessment, Lake Trout, Population Demographics, Population Genetics
Protecting Sources of Drinking Water for the M'Chigeeng First Nation, Manioulin Island, Ontario
The potential impacts of domestic wastewater (DWW) on the source of drinking water for the M’Chigeeng First Nation were monitored as part of the development of a Source Water Protection plan. During a period of continuous overflow of the Gaaming Wastewater Lagoon serving the community, the chemical tracers, caffeine and sucralose were tracked in West Bay with Passive Organic Chemical Integrative Samplers (POCIS). From the results, we speculated that DWI impacts could have been from three possible DWW sources. POCIS deployed above and below the thermocline indicated a higher mean sucralose concentration of 2.52 ± 1.83 ng/L in the hypolimnion of West Bay relative to mean epilimnetic sucralose concentrations of 0.56 ± 0.02 ng/L, suggesting possible wastewater percolation with an estimated time of travel of 61.5 days. Microbial loads of 200 CFU/100 ml E. coli from the lagoon overflow into Mill Creek decreased to 60 CFU/100 ml before entering West Bay. West Bay’s wastewater assimilative capacity met Provincial Water Quality Objectives in the epilimnion and hypolimnion except for dissolved oxygen in the hypolimnion at 4.16 ± 1.86 mg/L, which is a threat to the onset of hypoxia for fish (i.e. <5 mg/L). Assimilative capacity results support a Fall lagoon discharge. Author Keywords: caffeine, drinking water, Passive Organic Chemical Integrative Samplers (POCIS), sucralose, thermocline, wastewater
Wastewater Impacts on Freshwater Mussels and Water Quality in a Tributary of the Lower Grand River in Southwestern Ontario, Canada
The main goal of this thesis was to assess the potential impacts of discharges of treated effluent from a small facultative sewage lagoon serving approximately 300 residents of the Mississaugas of the Credit First Nation to freshwater mussel populations in Boston Creek, a small tributary of the lower Grand River. The current resident mussel populations inhabiting Boston Creek were assessed using semi-qualitative visual surveying methods. In addition to various population level observations, other possible point and non-point influences on water quality in Boston Creek were identified. Following this, Lasmigona costata mussels were deployed as biomonitoring organisms alongside passive samplers during the October 2017 lagoon discharge period. Time weighted average (TWA) concentrations of select Contaminants of Emerging Concern (CECs) and Polycyclic Aromatic Hydrocarbons (PAHs) were estimated from levels of these compounds accumulated on passive samplers to understand the influence of wastewater on water quality in Boston Creek. Finally, mussel tissues were analyzed for various biomarkers of exposure to contaminants. Population surveys indicated that Boston Creek supports a plentiful and diverse community of freshwater mussels and may be a refuge for the Species of Special Concern, Villosa iris. Passive sampling revealed that most PAHs measured were present at concentrations below detection limits, while CECs were typically detected at relatively low concentrations (ng/L) directly downstream of the lagoon discharge. Biomarker responses detected in Lasmigona costata generally could not be attributed to exposure to the lagoon effluent but these data may indicate response to other point and non-point sources of pollution that could be affecting resident freshwater mussel populations in Boston Creek. The mussels surveyed in Boston Creek may be displaying community level effects of exposure to other sources of pollution in the area. The results of this thesis will help in establishing water quality guidelines in the lower Grand River watershed that will assist in the recovery strategy for freshwater mussel species at risk in Ontario. Author Keywords: Biomarkers, Biomonitoring, CECs, First Nations, Freshwater Mussels, SAR
Characterizing the demographic history and prion protein gene variation to infer susceptibility to chronic wasting disease in a naïve population of white-tailed deer (Odocoileus virginianus)
Assessments of the adaptive potential of natural populations are essential for understanding and predicting responses to environmental stressors like climate change and infectious disease. The range of stressors species face in a human-dominated landscape, often have contrasting effects. White-tailed deer (Odocoileus virginianus, deer) are expanding in the northern part of their range following decreasing winter severity and increasing forage availability, caused by climate change. Chronic wasting disease (CWD), a prion disease affecting cervids, is likewise expanding and represents a major threat to deer and other cervids We obtained tissue samples from free-ranging deer across their native range in Ontario, Canada which has yet to detect CWD in wild populations of cervids. High throughput sequencing was used to assess neutral genomic variation and variation in the gene responsible for the protein that misfolds into prions when deer contract CWD, known as the PRNP gene. Neutral variation revealed a high number of rare alleles and no population structure, consistent with an expanding population of deer. Functional genetic variation revealed that the frequencies of variants associated to CWD susceptibility and disease progression were evenly distributed across the landscape and the frequencies were consistent with deer populations not infected with CWD. These findings suggest that an observable shift in PRNP allele frequencies likely coincides with the start of a novel CWD epidemic. Sustained surveillance of genomic and genetic variation can be a useful tool for CWD-free regions where deer are managed for ecological and economic benefits. Author Keywords: Canadian wildlife, population genetics, prion, PRNP, RADseq, ungulate
Nitrogen and phosphorus bioavailability in soil amended with alkaline stabilized biosolids
Agricultural land application of biosolids recycles nutrients and organic matter to the soil, however the effect of treatment process on nutrient availability requires further research for better nutrient management. This study examined the bioavailability of nitrogen (N) and phosphorus (P) in alkaline treated biosolids (TB) when amended into three different soils. Despite a 45% reduction in total N and P content during treatment, TB did not show reduced N or P availability compared with sewage sludge (SS). Results of a corn growth experiment and a soil incubation showed that TB amendment resulted in little mineralization and generally net immobilization of N, and 2% total P availability to corn from TB. Results suggest that TB are not a source of bioavailable N in the short-term, but can be used as a P amendment for corn. Nutrient management of agricultural land receiving these materials should focus on P added and liming properties. Author Keywords: Alkaline treated biosolids, Nitrogen, Phosphorus, Soil fertility
Relationships between bird densities and distance to mines in Northern Canada
Increased mining activity in the Canadian Arctic has resulted in significant changes to the environment that may be influencing some tundra-nesting bird populations. In this thesis I examine the direct and indirect effects of mining on birds nesting in the Canadian Arctic. I first perform a literature review of the effects that mining in the Arctic has on northern environments and wildlife and outline several ways in which mines affect Arctic-breeding birds. By using the Program for Regional and International Shorebird Monitoring (PRISM) Arctic plot-based bird survey data from across the Canadian Arctic, collected from 1995 to 2018, I identify the effects of distance to mining operations on the occupancy patterns of Arctic-breeding bird species. Six species’ densities were significantly impacted by mine proximity (Canada/Cackling Goose, Long-tailed Duck, Long-tailed Jaeger, Pectoral Sandpiper, Savannah Sparrow, and Rock Ptarmigan) across five major mine sites. Each species has its own unique relationship to distance from mining activity. Author Keywords: Bird populations, Canadian Arctic, Mining, Mining activities, PRISM, Tundra-nesting birds
Biosynthesis and impact of cytokinins on growth of the oyster mushroom, Pleurotus ostreatus
The oyster mushroom, Pleurotus ostreatus, is one of the most widely cultivated edible basidiomycetes. It has gained increased attention for its economic, environmental, and medicinal properties. While a lot is known about cytokinins (CKs) and their actions at the molecular and cellular levels in plants, much less is known about the function of CKs in other kingdoms. Cytokinins, which have been detected in several fungal species, play a role in pathogenic attack against plants or during plant growth promotion by plant beneficial microbes; however, the role of CKs in fungal physiology, separate from plant associations remains largely unknown. This thesis focuses on the occurrence of fungal-derived CKs in P. ostreatus when grown in vitro as submerged or aerial mycelium. Cytokinin profiling by UHPLC-HRMS/MS revealed that P. ostreatus produces CKs and that the tRNA degradation pathway is the main source of these molecules. CK dynamics within fungal growth supported previous evidence, which suggested that tRNA degradation products have a role in the physiological development of fungi for which CKs act as fungal growth regulators. A second component of the thesis demonstrated that P. ostreatus responds to exogenous applications of aromatic and isoprenoid CKs and their effects were dependent on the dose and CK type. N6-Benzyladenine (BAP), Kinetin (KIN), N6-isopentenyladenine (iP), and trans-zeatin (tZ) bioassays revealed hormone-type responses (hormesis: biphasic response). At low doses, mycelium growth could be stimulated, whereas, at high doses only inhibitory effects were observed. This stimulation/inhibition was observed whether the measured response was an increase/decrease of aerial mycelium colony diameter, biomass accumulation or a change in mycelium morphology as compared to the controls. Results indicated there is potential to alter mycelium growth and development of P. ostreatus; thus, CKs may play the role of a “mycohormone” and may be specifically helpful for medicinal fungi by increasing growth and efficiency to produce many biologically active substances with valuable medical and environmental applications. Author Keywords: cytokinins, fungal-derived CKs, hormesis, mycelium, mycohormone, Pleurotus ostreatus
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
Genetic diversity and differentiation of Ontario’s recolonizing fishers (Pekania pennanti)
Fishers (Pekania pennanti) were extirpated from many parts of Ontario in the early 20th century, but as of the early 2000s the species had recolonized most of its historical range. While the primary population genetic structure of fishers in central and eastern Ontario has not changed drastically over the past ten years, we did find evidence of increased secondary structure and a reduction in northward movement from southeastern Ontario, a site of recent immigration from the Adirondacks in northern New York. This may be indicative of a reduction in density and thus in density-dependent migration, or it may be a consequence of the population reaching equilibrium following a period of rapid expansion associated with recolonization. We also observed no variation within central and eastern Ontario at 14 of 15 candidate functional loci we screened, suggesting possible directional or stabilizing selection and a lack of adaptive potential. Author Keywords: fisher, functional genes, Ontario, Pekania pennanti, population genetics, recolonization
Frog Virus 3
Understanding the maintenance and spread of invasive diseases is critical in evaluating threats to biodiversity and how to best minimize their impact, which can by done by monitoring disease occurrences across time and space. I sought to apply existing and upcoming molecular tools to assess fluctuations in both presence and strain variation of frog virus 3 (FV3), a species of Ranavirus, across Canadian waterbodies. I explored the temporal patterns and spatial distribution of ranavirus presence across multiple months and seasons using environmental DNA techniques. Results indicate that ranavirus was present in approximately 72.5% of waterbodies sampled on a fine geographical scale (<10km between sites, 7,150 km2), with higher detection rates in later summer months than earlier. I then explored the sequence variability at the major capsid protein gene (MCP) and putative virulence gene (vIF-2α) of FV3 samples from Ontario, Alberta, and the Northwest Territories, with the premise of understanding pathogen movement across the landscape. However, a lack of genetic diversity was found across regions, likely due to a lack of informative variation at the chosen genetic markers or lack of mutation. Instead, I found a novel FV3-like ranavirus and evidence for a recombinant between FV3 and a ranavirus of another lineage. This thesis provides a deeper understanding into the spatio-temporal distribution of FV3, with an idea of how widespread and threatening ranaviruses are to amphibian diversity. Keywords: ranavirus, frog virus 3, amphibians, environmental DNA, phylogenetics, wildlife disease, disease surveillance, major capsid protein, vIF-2α Author Keywords: amphibians, environmental DNA, frog virus 3, phylogenetics, ranavirus, wildlife disease
Carbon and Nitrogen Isotope Changes in Streams along an Agricultural Gradient
Nitrogen is a major constituent of agricultural fertilizers, and nitrogen inputs to stream water via runoff and groundwater lead to a variety of negative environmental impacts. In order to quantify the movement of nitrogen through aquatic food webs, fourteen streams with varying land uses across South-Central Ontario were sampled for two species of fish, freshwater mussels, and water for measurement of isotope ratios of δ15N and δ13C. I found that nitrogen isotopes in fish, water, and mussels were related to the percentage of riparian monoculture, and that carbon isotopes were unrelated to monoculture. Though all species were enriched as monoculture increased, the rate of δ15N enrichment as monoculture increased did not vary between species. This study has improved our understanding of how monoculture affects nutrient enrichment in stream food webs, and assesses the validity of using nitrogen isotopes to measure trophic positions of aquatic organisms across an environmental gradient. Author Keywords: agriculture, fish, food webs, nitrogen, stable isotopes, streams

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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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