Graduate Theses & Dissertations

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Reintroducing species in the 21st century
Climate change has had numerous impacts on species' distributions by shifting suitable habitat to higher latitudes and elevations. These shifts pose new challenges to biodiversity management, in particular translocations, where suitable habitat is considered crucial for the reintroduced population. De-extinction is a new conservation tool, similar to reintroduction, except that the proposed candidates are extinct. However, this novel tool will be faced with similar problems from anthropogenic change, as are typical translocation efforts. Using ecological niche modelling, I measured suitability changes at translocation sites for several Holarctic mammal species under various climate change scenarios, and compared changes between release sites located in the southern, core, and northern regions of the species' historic range. I demonstrate that past translocations located in the southern regions of species' ranges will have a substantial decline in environmental suitability, whereas core and northern sites exhibited the reverse trend. In addition, lower percentages (< 50% in certain scenarios) of southern sites fall above the minimal suitability threshold for current and long-term species occurrence. Furthermore, I demonstrate that three popular de-extinction candidate species have experienced changes in habitat suitability in their historic range, owing to climate change and increased land conversion. Additionally, substantial increase in potentially suitable space is projected beyond the range-limits for all three species, which could raise concerns for native wildlife if de-extinct species are successfully established. In general, this thesis provides insight for how the selection of translocation sites can be more adaptable to continued climate change, and marks perhaps the first rigorous attempt to assess the potential for species de-extinction given contemporary and predicted changes in land use and climate. Author Keywords: climate change, de-extinction, ecological niche models, MaxEnt, reintroduction, translocation
ADAPT
This thesis focuses on the design of a modelling framework consisting of loose-coupling of a sequence of spatial and process models and procedures necessary to predict future flood events for the years 2030 and 2050 in Tabasco Mexico. Temperature and precipitation data from the Hadley Centers Coupled Model (HadCM3), for those future years were downscaled using the Statistical Downscaling Model (SDSM4.2.9). These data were then used along with a variety of digital spatial data and models (current land use, soil characteristics, surface elevation and rivers) to parameterize the Soil Water Assessment Tool (SWAT) model and predict flows. Flow data were then input into the Hydrological Engineering Centers-River Analysis System (HEC-RAS) model. This model mapped the areas that are expected to be flooded based on the predicted flow values. Results from this modelling sequence generate images of flood extents, which are then ported to an online tool (ADAPT) for display. The results of this thesis indicate that with current prediction of climate change the city of Villahermosa, Tabasco, Mexico, and the surrounding area will experience a substantial amount of flooding. Therefore there is a need for adaptation planning to begin immediately. Author Keywords: Adaptation Planning, Climate Change, Extreme Weather Events, Flood Planning, Simulation Modelling
Nutritional stoichiometry and growth of filamentous green algae (Family Zygnemataceae) in response to variable nutrient supply
In this study, I investigate the effects of nitrogen (N) and phosphorus (P) on the nutritional stoichiometry and growth of filamentous green algae of the family Zygnemataceae in situ and ex situ. I found a mean of Carbon (C):N:P ratio of 1308:66:1 for populations growing in the Kawartha Lakes of southern Ontario during the summer of 2012. FGA stoichiometry was variable, with much of the variation in algal P related to sediment P (p < 0.005, R2 = 0.58). Despite large variability in their cellular nutrient stoichiometry, laboratory analysis revealed that Mougeotia growth rates remained relatively consistent around 0.28 day-1. In addition, Mougeotia was found to be weakly homeostatic with respect to TDN:TDP supply (1/HNP = 0.32). These results suggest that FGA stoichiometry and growth rates are affected by sediment and water N and P. However, they will likely continue to grow slowly throughout the summer despite variable nutrient supply. Author Keywords: Chlorophyll concentration, Filamentous algae, Growth rate, Homeostatic regulation, Nutritional stoichiometry
Early Responses of Understory Vegetation to Above Canopy Nitrogen Additions in a Jack Pine Stand in Northern Alberta
Abstract Early Responses of Understory Vegetation After One Year of Above Canopy Nitrogen Additions in a Jack Pine Stand in Northern Alberta Nicole Melong Nitrogen (N) emissions are expected to increase in western Canada due to oil and gas extraction operations. An increase in N exposure could potentially impact the surrounding boreal forest, which has adapted and thrived under traditionally low N deposition. The majority of N addition studies on forest ecosystems apply N to the forest floor and often exclude the important interaction of the tree canopy. This research consisted of aerial NH4NO3 spray applications (5, 10, 15, 20, 25 kg N ha-1yr-1) by helicopter to a jack pine (Pinus banksiana Lamb.) stand in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada. The main objective was to assess the impacts of elevated N after one year of treatment on the chemistry of understory vegetation, which included vascular plants, terricolous lichens, epiphytic lichens and a terricolous moss species. Changes in vegetation chemistry are expected to be early signs of stress and possible N saturation. Increased N availability is also thought to decrease plant secondary compound production because of a tradeoff that exists between growth and plant defense compounds when resources become available. Approximately 60% of applied N reached the ground vegetation in throughfall (TF) and stemflow (SF). Nitrate was the dominant form of N in TF in all treated plots and organic N (ON) was the dominant form of N in SF in all plots. The terricolous non-vascular species were the only understory vegetation that responded to the N treatments as N concentration increased with increased treatment. Foliar chemistry of the measured epiphytic lichens, vascular species, and jack pine was unaffected by the N treatments. Based on biomass measurements and N concentration increases, the non-vascular terricolous species appear to be assimilating the majority of TF N after one year. Vegetation from the high treatment plot (25 kg N ha-1yr-1) was compared to a jack pine forest receiving ambient high levels of N (21 kg N ha-1yr-1) due to its proximity to Syncrude mining activities. Nitrogen concentrations in plant tissues did not differ between the two sites; however, other elements and compounds differed significantly (Ca, Mg, Al, Fe). After one year of experimental N application, there were no environmental impacts consistent with the original N saturation hypothesis. Author Keywords: Athabasca Oil Sands Region, Canopy Interactions, Jack Pine, Nitrogen, Secondary Chemistry, Understory Vegetation
Longitudinal trends of benthic invertebrates in regulated rivers
The Serial Discontinuity Concept describes the downstream recovery of key biophysical variables below an impoundment. With the proliferation of hydropower dams to meet increasing societal demands, further refinement and understanding of the Serial Discontinuity Concept is needed to accurately predict downstream impacts and ensure the proper management of rivers. In this study, I examine SDC predictions on physical, chemical and biological recovery in regulated rivers providing evidence from 1) a comprehensive literature review and 2) a formal test using two regulated rivers in Northern Ontario. I specifically address how these changes are reflected in benthic invertebrate abundance, diversity, and community composition. The literature review and case studies support the predicted recovery of temperature, periphyton, substrate, and drift. In addition, the study suggests that two recovery gradients exist in regulated rivers: 1) a longer, thermal gradient taking up to hundreds of kilometres downstream; and 2) a shorter, resource subsidy gradient recovering within 1-4 km downstream of an impoundment. Total benthic invertebrate abundance varies considerably and depends on the degree of flow alteration and resource subsidies from the upstream reservoir. In contrast, benthic diversity is reduced below dams irrespective of dam location and operation with little recovery observed downstream. Contrary to SDC predictions, the longitudinal gradient in regulated rivers is not a compaction of functional changes seen over several stream orders in natural rivers but a response to dam design and reservoir conditions. Stoneflies and dragonflies are particularly sensitive to regulation while filter feeding invertebrates are enhanced. Ward and Stanford's (1983) Serial Discontinuity Concept is still a useful framework for testing hypotheses. Future studies should further expand the SDC through empirical estimation within the context of the landscape to gain a better scientific understanding of regulated river ecology. Author Keywords: benthic invertebrates, dams, longitudinal, recovery, River Continuum Concept, Serial Discontinuity Concept
Speciation of Aluminum and Zinc in Three Streams of a Forested Catchment of the Boreal Zone
This study presents a detailed assessment of the chemical speciation of aluminum and zinc in three streams of a small, acid-sensitive forested catchment on the southern edge of the Precambrian Shield. Speciation analysis was achieved using an in-situ analytical technique known as Diffusive Gradient in Thin film (DGT) which measures labile metals, and a predictive computer algorithm (WHAM VI) which calculates metal species concentrations. Three types of DGT with different metal scavenging capabilities were used and a total of 11 deployments performed across four seasons. WHAM VI predictions showed that the organic fraction of aluminum was the main contributor to the dissolved concentrations in the main inflow stream (PC1) (~ 80 %) and the lake's outflow (PCO) (~ 75%); in the upland stream (PC1-08) the inorganic fraction contributed ~ 75%. For zinc the free ion was the single most important contributor to the dissolved concentration (< 90%) in all three streams. A comparative study of the DGT and WHAM methods showed an agreement between their inorganic concentrations during the spring season. Both methods indicate the greatest environmental impact for Al takes place during snow melt period in PCO and PC1-08 and in the summer for PC1. The greatest environmental impact for Zn predicted with WHAM VI, occurs during the spring in all three streams. Author Keywords: Aluminum, DGT, Metal speciation, WHAM, Zinc
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
Fate of Silver Nanoparticles in Lake Mesocosms
The fate of silver nanoparticles (AgNPs) in surface waters determines the ecological risk of this emerging contaminant. In this research, the fate of AgNPs in lake mesocosms was studied using both a continuous (i.e. drip) and one-time (i.e. plug) dosing regime. AgNPs were persistent in the tested lake environment as there was accumulation in the water column over time in drip mesocosms and slow dissipation from the water column (half life of 20 days) in plug mesocosms. In drip mesocosms, AgNPs were found to accumulate in the water column, periphtyon, and sediment according to loading rate; and, AgNP coating (PVP vs. CT) had no effect on agglomeration and dissolution based on filtration analysis. In plug mesocosms, cloud point extraction (CPE), single-particle-inductively coupled mass spectroscopy (spICP-MS), and asymmetrical flow field-flow fractionation (AF4-ICP-MS) confirmed the temporal dissolution of AgNPs into Ag+ over time; however, complexation is expected to reduce the toxicity of Ag+ in natural waters. Author Keywords: AF4-ICP-MS, cloud point extraction, fate, mesocosms, silver nanoparticles, SP-ICP-MS
Development and Use of Passive Samplers for Monitoring Dissolved and Nanoparticulate Silver in the Aquatic Environment
Silver nanoparticles (nAg) are the largest and fastest growing class of nanomaterials, and are a concern when released into aquatic environments even at low μg L-1+). Diffusive gradient in thin films (DGT) with a thiol-modified resin were used to detect labile silver and carbon nanotubes (CNT-sampler) were used to measure nAg. Laboratory uptake experiments in lake water provided an Ag+ DGT diffusion coefficient of 3.09 x 10 -7 cm2s-1 and CNT sampling rates of 24.73, 5.63, 7.31 mL day-1, for Ag+, citrate-nAg and PVP-nAg, respectively. The optimized passive samplers were deployed in mesocosms dosed with nAg. DGT samplers provided estimated Ag+ concentrations ranging from 0.15 to 0.98 μg L-1 and CNT-samplers provided nAg concentrations that closely matched measured concentrations in water filtered at 0.22 μm. Author Keywords: ICP-MS, mesocosms, nanoparticles, nanosilver, passive sampling
Models of partitioning, uptake, and toxicity of neutral organic chemicals in fish
Models of partitioning, uptake, and toxicity of neutral organic chemicals in fish Alena Kathryn Davidson Celsie A novel dynamic fugacity model is developed that simulates the uptake of chemicals in fish by respiration as applies in aquatic toxicity tests. A physiologically based toxicokinetic model was developed which calculates the time-course of chemical distribution in four tissue compartments in fish, including metabolic biotransformation in the liver. Toxic endpoints are defined by fugacity reaching a 50% mortality value. The model is tested against empirical data for the uptake of pentachloroethane in rainbow trout and from naphthalene and trichlorobenzene in fathead minnows. The model was able to predict bioconcentration and toxicity within a factor of 2 of empirical data. The sensitivity to partition coefficients of computed whole-body concentration was also investigated. In addition to this model development three methods for predicting partition coefficients were evaluated: lipid-fraction, COSMOtherm estimation, and using Abraham parameters. The lipid fraction method produced accurate tissue-water partitioning values consistently for all tissues tested and is recommended for estimating these values. Results also suggest that quantum chemical methods hold promise for predicting the aquatic toxicity of chemicals based only on molecular structure. Author Keywords: COSMOtherm, fish model, fugacity, Partition coefficient, tissue-water, toxicokinetics
CO2 dynamics of tundra ponds in the low-Arctic Northwest Territories, Canada
Extensive research has gone into measuring changes to the carbon storage capacity of Arctic terrestrial environments as well as large water bodies in order to determine a carbon budget for many regions across the Arctic. Inland Arctic waters such as small lakes and ponds are often excluded from these carbon budgets, however a handful of studies have demonstrated that they can often be significant sources of carbon to the atmosphere. This study investigated the CO2 cycling of tundra ponds in the Daring Lake area, Northwest Territories, Canada (64°52'N, 111°35'W), to determine the role ponds have in the local carbon cycle. Floating chambers, nondispersive infrared (NDIR) sensors and headspace samples were used to estimate carbon fluxes from four selected local ponds. Multiple environmental, chemical and meteorological parameters were also monitored for the duration of the study, which took place during the snow free season of 2013. Average CO2 emissions for the two-month growing season ranged from approximately -0.0035 g CO2-C m-2 d-1 to 0.12 g CO2-C m-2 d-1. The losses of CO2 from the water bodies in the Daring Lake area were approximately 2-7% of the CO2 uptake over vegetated terrestrial tundra during the same two-month period. Results from this study indicated that the production of CO2 in tundra ponds was positively influenced by both increases in air temperature, and the delivery of carbon from their catchments. The relationship found between temperature and carbon emissions suggests that warming Arctic temperatures have the potential to increase carbon emissions from ponds in the future. The findings in this study did not include ebullition gas emissions nor plant mediated transport, therefore these findings are likely underestimates of the total carbon emissions from water bodies in the Daring Lake area. This study emphasizes the need for more research on inland waters in order to improve our understanding of the total impact these waters may have on the Arctic's atmospheric CO2 concentrations now and in the future. Author Keywords: Arctic, Arctic Ponds, Carbon dioxide, Carbon Fluxes, Climate Change, NDIR sensor
Aeolian Impact Ripples in Sand Beds of Varied Texture
A wind tunnel study was conducted to investigate aeolian impact ripples in sand beds of varied texture from coarsely skewed to bimodal. Experimental data is lacking for aeolian megaripples, particularly in considering the influence of wind speed on ripple morphometrics. Additionally, the modelling community requires experimental data for model validation and calibration. Eighteen combinations of wind speed and proportion of coarse mode particles by mass were analysed for both morphometrics and optical indices of spatial segregation. Wind tunnel conditions emulated those found at aeolian megaripple field sites, specifically a unimodal wind regime and particle transport mode segregation. Remote sensing style image classification was applied to investigate the spatial segregation of the two differently coloured size populations. Ripple morphometrics show strong dependency on wind speed. Conversely, morphometric indices are inversely correlated to the proportion of the distribution that was comprised of coarse mode particles. Spatial segregation is highly correlated to wind speed in a positive manner and negatively correlated to the proportion of the distribution that was comprised of coarse mode particles. Results reveal that the degree of spatial segregation within an impact ripple bedform can be higher than previously reported in the literature. Author Keywords: Aeolian, Impact Ripples, Megaripple, Self-organization, Wind Tunnel

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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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