Biological Sciences - Theses, Dissertations, and other Required Graduate Degree Essays

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Slime, safety and shorebirds: Biofilm production and grazing by migrating western sandpipers (Calidris mauri)

Author: 
Date created: 
2019-04-05
Abstract: 

The quality of stopover sites for migrant shorebirds is thought to be determined by food availability and safety from predators. This thesis investigates this interaction on an estuarine mudflat in British Columbia, where migrant western sandpipers graze biofilm. I measured biofilm concentration and grazing intensity on transects across the mudflat. I found that the concentration of biofilm rose 4.1 mg m-2 hr-1 during tidal emersion periods, with total accumulation matching that removed by sandpipers during grazing visits. During the higher-intensity (10 – 100 fold, based on daily sandpiper counts) northward migration, biofilm concentration increased and grazing decreased with proximity to the shoreline. In contrast, during southward migration biofilm was uniformly high. A danger manipulation experiment supported a trade-off with biofilm concentration: grazing declines with danger, but less so where biofilm is higher. Together the results indicate that dynamic trophic interactions between danger, sandpipers and biofilm create spatial patterns in biofilm concentration.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Ron Ydenberg
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

The effects of diluted bitumen on marine intertidal vascular plants

Author: 
Date created: 
2019-01-29
Abstract: 

Canada has the third largest oil reserves in the world, most of which exist in the form of bitumen in the oil sands of the Western Canada Sedimentary Basin. Plans are underway to increase the export of petroleum products including diluted bitumen (dilbit) and crude oil to overseas markets, highlighting the potential risk of a spill into the Canadian marine environment. Understanding and evaluating risk, and the development of chemical management plans require information on the toxicity of dilbit to key marine species. Little information exists regarding the toxic effects of most petroleum products to intertidal vascular plants. The objective of this project was to determine the lethal and sublethal toxicity of environmentally relevant concentrations of dilbit to eelgrass (Zostera marina), an intertidal vascular plant and keystone species in the Pacific Northwest. Eelgrass was collected from the intertidal zone of an uncontaminated site in the Strait of Georgia, near Boundary Bay, British Columbia. A short-term, 9-d exposure and a long-term 28-d exposure of shoots to multiple concentrations of a water-accommodated fraction (WAF) of dilbit were performed. Endpoints assessed in shoots from the short-term exposure included: total reactive oxygen species (ROS), activity of catalase and superoxide dismutase, and protein oxidation. Shoots from the long-term exposure were assessed for biological endpoints including plant growth, chlorophyll-a content, and the effective quantum yield of Photosystem II.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Christopher Kennedy
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.

The effects of diluted bitumen and the dispersant Corexit 9500A on Pacific marine organisms

Date created: 
2019-03-07
Abstract: 

Canada is expected to significantly increase the production and exportation of bitumen in the next decade. Raw bitumen is diluted with natural-gas condensates to produce diluted bitumen (dilbit), facilitating its flow through pipelines. Few data currently exist on dilbit toxicity to Pacific marine species, either alone or in combination with recently approved chemical dispersant Corexit 9500A. The current study investigated the toxicity of the water-accommodated fraction (WAF) of dilbit, Corexit 9500A, and the chemically enhanced water-accommodated fraction (CEWAF) of dilbit to representative marine species of the west coast of Canada. Oil chemically dispersed by Corexit showed evidence of higher toxicity than dilbit WAF to each test species including juvenile mysids (Mysidopsis bahia), juvenile topsmelt (Atherinops affinis) and adults spot prawns (Pandalus platyceros). Additionally, purple sea urchin (Strongylocentrous purpuratus) fertilization showed high susceptibility to Corexit toxicity, both with and without dilbit present, as nearly 100% of eggs exposed to Corexit remained unfertilized. Overall these results suggest that the use of Corexit as a remediation technique may increase the toxic impacts to Pacific marine species over those caused by a dilbit spill alone.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Dr. Christopher Kennedy
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.

The role of Kdnase (sialidase) in cell wall integrity and virulence of Aspergillus fumigatus

Author: 
Date created: 
2018-08-17
Abstract: 

Aspergillus fumigatus is the leading airborne fungal pathogen worldwide. In immunocompromised individuals, exposure to conidiospores can lead to an infection known as invasive aspergillosis. We have previously shown that A. fumigatus possesses a sialidase that preferentially cleaves the sialic acid, Kdn (3-deoxy-d-glycero-d-galacto-2-nonulosonic acid) and is therefore a Kdnase. The purpose of my research was to characterize a Δkdnase knockout strain. Under hyperosmotic stress, cell wall α-glucan and chitin levels were significantly increased in Δkdnase hyphae compared to wild type (WT). Δkdnase was more susceptible to growth inhibition by amphotericin B and caspofungin but resistant to nikkomycin. Virulence of the Δkdnase strain in neutropenic mice was attenuated compared to WT when mice were also treated with amphotericin B, but not in the absence of the drug. uHPLC-MS analysis showed that WT and Δkdnase conidiospores, and WT hyphae contained Kdn; however, Kdn was not detectable in Δkdnase hyphae.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Margo Moore
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

Semiochemical communication between yellowjacket wasps and their yeast symbionts

Author: 
Date created: 
2018-07-03
Abstract: 

My research investigated whether (i) symbiotic yeasts isolated from the digestive tract of social wasps, (ii) commercial yeasts, or (iii) the volatiles these yeasts produce can be used as trap baits for capturing yellowjackets. I found that adding brewer’s yeast to dried fruit and fruit powder enhanced attraction of yellowjackets in Argentina. I also found that the two yeast species Hanseniaspora uvarum and Lachancea thermotolerans, isolated from North American yellowjackets and grown on grape juice-infused agar, attract yellowjackets. Lachancea thermotolerans in admixture with fruit powder was also attractive and expressed an additive effect when combined with a commercial wasp lure. Synthetic analog blends of the volatiles produced by H. uvarum growing on grape juice-infused media and L. thermotolerans growing on fruit powder were both attractive to western yellowjackets, but not to other yellowjackets. In summary, symbiotic yeasts and their semiochemicals, respectively, show potential as yellowjacket trap baits or lures.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Gerhard Gries
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.P.M.

Hepatic gene profile analysis for chronic exposure of clothianidin in early life stage sockeye salmon (Oncorhynchus nerka)

Date created: 
2018-06-25
Abstract: 

This study investigated the effects of the neonicotinoid insecticide clothianidin on hepatic gene expression in juvenile sockeye salmon. Four genetically distinct pairs of wild sockeye salmon were collected and fertilized in clean water, and were subsequently exposed to 0.15, 1.5, 15, 150 μg/L clothianidin from 1 hour post-fertilization through to the swim-up fry developmental stage. Individual swim-up fry livers from all genetic crosses and each treatment were collected and various genes of interest were quantified using quantitative PCR. The genes of interest evaluated in this study were estrogen receptor alpha and beta 2, cytochrome P450 1A, suppressor of cytokine signaling 3, and glucocorticoid receptor 2. The glucocorticoid receptor 2 showed a significant 4-fold downregulation at 150 μg/L compared to the control treated fish (p <0.05). This study indicates the utility of quantitative PCR in these early life-stage studies and potential impacts on the stress axis after prolonged exposure to clothianidin.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Vicki Marlatt
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.

Effects of the aquatic herbicide, Reward®, on the Fathead minnow and Northwestern Salamander

Date created: 
2018-05-24
Abstract: 

In this study the commercial formulation of the aquatic herbicide Reward® (active ingredient diquat dibromide [DB]) was tested. In larval and adult Fathead minnows (Pimephales promelas; FHM) after two 24 h pulse exposures spaced two weeks apart the LC50’s of 4.19 mg/L and 6.71 mg/L were obtained, respectively. A lowest observed effect concentration of 1.18 mg/L for larval growth in FHMs during a 7 d continuous exposure was also derived. An acute 96 h LC50 of 71.5 mg/L DB was obtained for Northwestern salamander (Ambystoma gracile) larvae, while a 21 d continuous exposure LC50 was dramatically lower (1.56 mg/L DB) for these larvae. Few reports of environmental concentrations of this pesticide could be found for Canadian waters. Whether aquatic and/or terrestrial applications and/or DB’s persistent nature in sediments translate into acute or sub-chronic toxicity exposure scenarios in Canadian aquatic systems is unknown and should be the focus of future studies.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Vicki Marlatt
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

River network structuring of climate and landscape effects in salmon watersheds

Author: 
Date created: 
2019-01-09
Abstract: 

Climate change is altering historic patterns of temperature and precipitation worldwide with significant implications for the abiotic and biotic dynamics of river ecosystems. Flowing downhill, precipitation aggregates into creeks, streams and eventually rivers, forming a branching network over the landscape architecturally similar to the branches, limbs and trunk of a tree. Linking disparate locations, these river networks integrate the varied expressions of climate within a watershed. Thus, the river network offers a framework for understanding how spatial patterns of climate are organized and become manifest in rivers. By considering the river network's structuring of climate and landscape interactions, we might better understand how climate and land-use change impact river ecosystems and more clearly identify particularly vulnerable biota. In chapter 2, I examine how river networks dampen signals of climate change in hydrologic flow by integrating varied flow trends from upstream. I demonstrate that by integrating a diverse climate portfolio, the network accumulates changing flow regimes of different volatility, direction and magnitude, such that on average downstream climate change trends are moderated. In chapter 3, I consider the match-mismatch potential of juvenile salmon migrating towards the springtime zooplankton resource pulse in the estuary. I show that populations further from, and whose climate is more dissimilar to, the estuary, are more likely to miss the peak zooplankton bloom. These findings suggest migratory distance influences phenological mismatch risk among populations. My fourth chapter develops an unsupervised machine learning method for cleaning stream temperature data to facilitate big data studies. In chapter 5, I gathered temperature data at over 100 locations throughout a watershed the size of Ireland, over 4 years at 2-hour intervals resulting in over 1 million data points. These data informed a spatial stream network model that quantified how landscape features and river connectivity control seasonal temperature dynamics. These temperature dynamics across space and time revealed that different adult salmon migrations have very different exposures to warm temperatures. Collectively, these findings illustrate that river networks: 1. integrate and dampen signals of climate change, 2. structure phenological match-mismatch patterns and 3. organize thermal exposure potential of biota.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Jonathan Moore
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

Non-lethal human-shark interactions and their ecological consequences

Date created: 
2018-10-31
Abstract: 

Collapses of predator populations, caused mainly by unsustainable fishing, have been documented in many marine ecosystems. Predators are thought to play critical roles in marine environments where, through direct predation and fear effects, they can shape demographic processes and community structure. My thesis focusses on the effects of two non-lethal anthropogenic impacts on sharks: prey depletion and shark provisioning tourism. Using stable isotopes and a time series of shark vertebrae, I first examine the historical isotope ecology of seven shark species from the southwest Indian Ocean. Two species with generalist diets showed no change over two decades in δ15N or δ13C signatures. Large individuals of five primarily piscivorous species exhibited isotope signatures that deviate from historical baselines, suggesting long-term changes in diet and/or foraging strategy. Next, I measure the effects of tourism-related provisioning on the trophic signatures and movement patterns of Caribbean reef sharks Carcharhinus perezi in the Bahamas. Combining stable isotope analyses, acoustic telemetry and direct observations, I show that individual sharks that are provisioned more frequently have elevated δ15N signatures, but similar residency and movement patterns to un-provisioned conspecifics, suggesting that their broader ecological roles are not affected by long-term provisioning. Finally, I use the gradient of shark abundance generated by provisioning for ecotourism to reveal the wider coral reef community corollaries of reef shark presence. Benthic community structure varied across this gradient, with less macroalgae and more turf algae at sites with more sharks. Herbivorous parrotfish were abundant but fed less selectively and consumed more macroalgae at sites with more sharks, suggesting that fear effects may drive the patterns observed. Teleost fish biomass was almost twice as high near the provisioning site than further away, a pattern driven by fisher avoidance of areas of more sharks. Effective shark conservation may thus deliver broad cascading benefits to coral reef communities. While most marine predator declines are due to direct fishing mortality, my thesis evokes additional mechanisms by which anthropogenic activities may drive change in predator populations and their communities.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Isabelle Côté
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

The pollination ecology of highbush blueberry (Vaccinium corymbosum) in British Columbia

Author: 
Date created: 
2018-05-28
Abstract: 

Agricultural systems often support low beneficial insect diversity because they reduce habitat quality. Agricultural management increases landscape homogeneity resulting in low habitat and resource diversity. Crops that rely on wild pollinators for fruit production or predators and parasitoids for pest control may lose access to these services as the agroecosystem becomes increasingly managed. I used yield data from pollination experiments conducted over four years, along with insect surveys, to better understand the dynamics between insect communities in agroecosystems and their use of the agricultural landscape in highbush blueberry (Vaccinium corymbosum) in the Fraser Valley of southern British Columbia, Canada. Regional land use was identified as being an important component in structuring beneficial insect communities. Semi-natural habitat, such as pasture or fallow, was found to support greater abundances and diversity of all beneficial insects. Land use with greater disturbance, like conventional non-flowering agriculture, reduced pollinator species richness but increased the abundance of generalist predators. The differences between groups in their response to land use types might be driven by variability in access to resources (ex. floral resources or pest insects) in the larger agricultural landscape. However, surrounding landscape composition did not affect blueberry yield deficit, which was instead determined primarily by bumble bee visits and minimum daily temperatures. This finding highlights the importance of weather conducive to pollinator foraging for crop production. Despite the importance of bumble bees for reducing yield deficit, experimental introduction of two managed bumble bee species did not mitigate these deficits. Differences in bumble bee species characteristics associated with reproduction predicted pollen forager recruitment, which when coupled with differences in foraging preferences (blueberry pollen comprised 50% of pollen loads in one species, but less than 20% in the other and in managed honey bees) provides some insight into which managed species is best suited for further commercial development. My results highlight the complexity associated with predicting crop pollination levels and demonstrate how the impact of wild insects on production will vary with surrounding land-use, species characteristics, and abiotic factors. In crops highly reliant on wild pollinators, like highbush blueberry, understanding the needs of beneficial insects may allow farmers to modify practices to improve ecosystem services.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Elizabeth Elle
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.