Faculty of Graduate Studies Online Theses

Permanent URI for this collectionhttps://hdl.handle.net/10222/11163

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Open Access
Beyond Passing: Reimagining Sites Adjacent to Transit Lines
(2025-09-09) Rasooli, Simin; No; Master of Architecture; School of Architecture; Not Applicable; Joyce Hwang; No; Cristina Verissimo; Catherine Venart
Transit lines often generate non-places—spaces of movement—shaped by efficiency and separated from civic life. This project explores how such spaces can be reimagined through continuity rather than interruption. By extending movement and allowing it to slow, overlap, and engage, transitional space becomes a threshold that supports presence and everyday life. The project looks at agora to understand how programs can be organized through historical and contemporary examples, such as arcades and courtyards, that show how movement shapes space. In doing so, it shifts the understanding from a purely functional definition toward grounded in programmatic interaction. Parking garages are studied as precedents where continuous movement defines form without fostering interaction. The thesis focuses on Gateway Station on the Expo Line in Surrey, BC—a growing transit hub with limited civic space—proposing the transformation of a transit-adjacent non-place into a civic environment responsive to urban rhythms and public needs.
Open Access
Agency as Praxis: A New Building for the Nova Scotia Association of Architects
(2025-09-09) Hawkes, Logan; Not Applicable; Master of Architecture; School of Architecture; Not Applicable; María Arquero de Alarcón; Not Applicable; Michael Faciejew; James Forren
This thesis begins from the observation that architects operate with diminished agency, constrained by market forces and institutional structures. Architecture’s historic pursuit of autonomy has contributed to this, distancing the discipline from political and social engagement. In response, the thesis proposes a design method that prioritizes process over outcome. Where fixed concepts risk closing possibilities, process allows for emergence—open-ended engagement where agency is enacted through continual decisions, translations, and adjustments. The method is structured around extradisciplinary models, architectural precedent, architectural representation, and iterative heuristics. It uses translation and abstraction not to impose meaning, but to draw it out. To test the method, a segment of professional basketball was analyzed, diagrammed, and transformed into nine architectural propositions—each corresponding to a floor in a building for the Nova Scotia Association of Architects. The resulting design embeds dynamic and unconventional spatial logics within a conventional frame, offering both critique and provocation.
Open Access
Understanding the Colonial Foundations of the Sri Lankan Civil War: Implications for Peacebuilding
(2025-08-31) Silva, Savandhi; Not Applicable; Master of Arts; Department of International Development Studies; Not Applicable; Daniel Salas - Gonzalez; Not Applicable; Nissim Mannathukkaren; Ajay Parasram
The Sri Lankan civil war (1983–2009) between the Sinhala-dominated state and the LTTE is often analysed in mainstream literature as a conflict rooted in discriminatory post-independence policies toward Tamils. While these accounts offer valuable insight into post-independence catalysts, they overlook the deeper structures that enabled a violent context to emerge. This study departs from such analyses by situating the trajectory of the conflict within the British colonial period (1815–1948). It examines administrative policies, constitutional reforms, and colonial ideologies that laid crucial foundations for civil war. Adopting a problematization of colonial structures as its methodological approach, the dissertation offers a critical re-narration of the war. In conclusion, it is argued that contextualizing the conflict within colonial legacies is vital for contemporary peacebuilding. Without this dimension, efforts risk reproducing the very structures that once facilitated violence, drastically limiting the prospects for peace.
Open Access
Sacred Place // Makerspace: Repointing St. Patrick’s Catholic Church
(2025-08-29) Basilio, Ceasar (Jam); Not Applicable; Master of Architecture; School of Architecture; Not Applicable; Joyce Hwang; Not Applicable; Catherine Venart; Michael Putman
As more churches close due to declining religious participation, many historic buildings are left empty and at risk. This thesis explores how the idea of sacredness can guide the transformation of St. Patrick’s Catholic Church in Halifax into a new kind of public space. Instead of replacing the church’s meaning, the project strengthens it, like repointing mortar between old bricks to help a wall stand strong. The proposal adds three new programs inside the church: a library at the front, maker pods in the center, and an exhibition space at the back. These are organized using the sequence of gate, path, and place. Each space supports learning, creativity, and reflection. Inspired by the church’s original role in serving the community, the project brings new life through practical use while respecting its sacred qualities. It offers a way to preserve sacred buildings by reimagining them with care and purpose.
Open Access
ASSOCIATION BETWEEN PREHOSPITAL AIRWAY MANAGEMENT AND 30-DAY SURVIVAL AND HYPOXIA: A 5-YEAR RETROSPECTIVE COHORT STUDY
(2025-08-31) Stirling, Jeffrey; Not Applicable; Master of Applied Science; Department of Community Health & Epidemiology; Received; n/a; Not Applicable; Judah Goldstein; Samuel Campbell; Sanja Stanojevic; Jill Hayden
Prehospital airway management in respiratory failure remains controversial, particularly around the timing and choice of advanced interventions. This retrospective observational study reviewed 756 Emergency Medical Services activations in Nova Scotia, Canada, from 2015–2019 involving cardiac arrest, trauma, or medical causes. Trends in device use, outcomes, and associations with 30-day survival and hypoxia were assessed for bag-valve-mask, supraglottic airways, and endotracheal intubation. BVM use declined sharply across all cohorts, while SGA adoption increased. ETI rates were stable in cardiac arrest cases but rose modestly in trauma and medical presentations. Care times were shorter with BVM, yet advanced airway attempts carried higher hypoxia risk. Adjusted analyses found no survival differences between devices in cardiac arrest, but in trauma and medical cases BVM use was associated with reduced 30-day mortality. These findings suggest growing reliance on SGAs and potential survival advantages of less invasive airway strategies, supporting refinement of EMS protocols.
Open Access
The Scottish Reynard: Robert Henryson's Interpretation of Reynardian Fables
(2025-08-30) Timmons, Alex; Not Applicable; Master of Arts; Department of English; Not Applicable; n/a; Not Applicable; Andrew Brown; Trevor Ross; Kathy Cawsey
In medieval Europe, fictional depictions of animals were very popular. These works of fiction offer insight into the ways in which animals were viewed in this time. Scottish poet Robet Henryson offers a unique example of the depiction of animals in beast literature because he bends the rules of the literary genres he is working with and advocates on the behalf of animals. This is particularly apparent when comparing his works with stories and traditions that he took inspiration from, such as the “Reynard the Fox” cycle of fables. In his transformation of this popular narrative, Henryson creates a vibrant animal world that also allows a human reader to respect and relate to the creatures that occupy it, as well as considering how they may be more like beasts than they believe.
Open Access
LINEAR SHRINKAGE PRECISION MATRIX METHOD FOR IMPROVED FUNCTIONAL CONNECTIVITY ESTIMATION IN NEUROIMAGING
(2025-08-14) Tan, Bei Ni; No; Master of Computer Science; Faculty of Computer Science; Not Applicable; n/a; No; Janarthanan Rajendran; Gabriel Spadon; Carlos Hernandez Castillo
Neurological disorders, arising from abnormalities in the nervous system, impose a major global health burden due to the lack of curative treatments and challenges in early diagnosis. Resting-state functional MRI (rs-fMRI) enables non-invasive mapping of brain activity, but conventional functional connectivity (FC) estimation often fails to capture complex network interactions. This study combines machine learning with shrinkage-based FC estimation to identify discriminative features that may serve as biomarkers across multiple disorders. Five FC methods—Pearson’s, Spearman’s, Empirical Covariance, Ledoit–Wolf, and Oracle Approximating Shrinkage—were compared using classifiers including Logistic Regression, SVM, Random Forests, KNN, Naive Bayes, and CNNs. L1-regularized models guided feature selection. Shrinkage-based estimators outperformed traditional methods, and a proposed Weighted Connectivity Matrix further improved accuracy, particularly with interpretable classifiers. Synthetic data confirmed robustness, and sensitivity analysis showed greatest influence from ROI count, followed by sample size. Results highlight the potential of shrinkage-based FC approaches for neuroimaging-based classification.
Open Access
ON OUR OWN TERMS: USING WÂHKÔHTOWIN AND MIYO-WÎCÊHTOWIN AS A NÊHIYAW RESPONSE TO ARTICLE 31 OF THE UNITED NATIONS DECLARATION ON THE RIGHTS OF INDIGENOUS PEOPLES
(2025-08-29) Lafond, Alphonsine; Not Applicable; Master of Laws; Faculty of Law; Not Applicable; Sara Ross; Not Applicable; Naiomi Metallic; Cheryl Simon
This thesis examines the role of nêhiyaw (the Plains Cree) “intellectual inheritance” within its legal order, framed through wâhkôhtowin and miyo-wîcêhtowin, and positions this as a legal response to Canada’s implementation of Article 31 of the United Nations Declaration on the Rights of Indigenous Peoples (the UN Declaration). It argues that the re-configuration of Canada’s domestic intellectual property regime for implementing Article 31 must be done through a broader, more fulsome approach that aligns with the UN Declaration’s overarching purpose: Indigenous self-determination. Rather than speak definitively on the nêhiyaw legal order, this thesis offers a potential framework for understanding it in relation to broader discussions on Indigenous intellectual property protection, with the aim of supporting legal revitalization efforts and underscoring the importance of Indigenous legal autonomy.
Open Access
Vacant to Vibrant: Reimagining Windsor’s Built Environment Through Community-Focused Design
(2025-07-29) Golovenko, Michael; Not Applicable; Master of Architecture; School of Architecture; Not Applicable; n/a; Not Applicable; Rashida Zakia Ng; Kenneth Acton; Diogo Burnay
The “hollow city” phenomenon affects many urban centres worldwide. The downtown core of Windsor, Ontario has struggled to deal with its many vacant buildings, surface-level parking lots, and underutilized spaces. Despite a strong local identity of artistic expression and agricultural availability the downtown lacks engaging, year-round public spaces for people to enjoy. This thesis proposes the creation of a permanent cultural anchor at the heart of downtown Windsor to counteract the “hollow city” effect and promote a sustainable urban future. By integrating an all-season farmers’ market with public art, and residential spaces, this centre will be the starting point for the city of Windsor to rebuild its downtown community. The project aims to foster community connections, revitalize the area, and showcase the transformation of a vacant space into a hub of continuous public interaction.
Open Access
PROBING THE DEGRADATION MECHANISMS OF LI-ION CELLS CONTAINING SILICON AND SINGLE-WALLED CARBON NANOTUBES
(2025-08-31) Dressler, Reid; No; Doctor of Philosophy; Department of Physics & Atmospheric Science; Not Applicable; Dr. Steen Schougaard; Yes; Dr. Theodore Monchesky; Dr. Ian Hill; Dr. Jeff Dahn
This work explores the improvements that can be made to energy density by changing the active materials within the negative electrode. Current batteries use graphite as the lithium-storing active anode material as it can reversibly incorporate lithium atoms efficiently and safely. Swapping graphite for a different kind of active material such as silicon presents many advantages but also many challenges surrounding lifetime. Silicon provides almost 10x the specific capacity of graphite and is incredibly abundant but experiences strong capacity fade due to its surface interaction with the electrolyte. The volume expansion silicon experiences during lithiation leads to constant parasitic chemical reactions and mechanical degradation leading to early cell failure. The introduction of a silicon anode in place of graphite improves stack energy density by up to 59%. The work done in this thesis explores alternative anode active materials including silicon and silicon based composite particles by evaluating their energy density and cycle life. Silicon active materials showed promising results when used in conjunction with single-walled carbon nanotubes and a conductive additive. The addition of carbon nanotubes to the electrode coating process allowed the use of common binders as it creates a strong electrical network between active particles that can withstand large volume changes. To further the development of silicon negative electrodes their degradation mechanisms and failure pathways in full cells must be fully understood. In-situ stack pressure, in-situ gas evolution and post cycling differential voltage analysis are used to pinpoint and track capacity loss mechanisms in full cells. These results highlight the failure of silicon based full cells as lithium inventory losses due to the constant SEI forming reactions on the anode. These results reinforce the need for engineered silicon composites that limit the particle volume fluctuations during cycling.
Open Access
OLFACTORY DISCRIMINATION, REVERSAL LEARNING AND OVERTRAINING EFFECTS IN NRXN1+/- AND NRXN1+/+ MICE IN AN OPERANT OLFACTOMETER
(2025-08-30) Ortibus, Wyatt; No; Master of Science; Department of Psychology and Neuroscience; Received; n/a; No; Dr. Simon Gadbois; Dr. Tamara Franklin; Dr. Ian Weaver; Dr. Richard Brown
Autism spectrum disorder (ASD) is characterized by deficits in social communication, social interaction, repetitive behaviours, and poor responses to social cues. ASD is most likely caused by multiple interactions between environmental and genetic factors, including the Neurexin (NRXN) family of membrane protein synaptic organizers. These proteins are implicated in neurodevelopmental disorders, such as ASD and schizophrenia, due to their unique functions at the synapse. Neurexins are encoded by three genes (Nrxn1, Nrxn2, and Nrxn3) and classified into three isoforms (α, β, and γ), all of which are thought to have specific functions at the synapse by binding to postsynaptic neuroligins. These cell adhesion proteins modulate synaptic transmission and downstream gene regulatory networks (e.g., DAT) that control neural function. Nrxn1 gene disruption leads to synaptic destabilization and cognitive impairment, suggesting that Nrxn1 may play an important role in learning and memory. Using an operant olfactometer, we tested cognitive flexibility in wild-type (C57BL/6J) and Nrxn1+/- mice, which were developed as a model for human autism. We used rodent translational studies to examine the cognitive and behavioral consequences of alterations (e.g., knockdowns) in the Nrxn1 genes. Our novel Nrxn1+/- mice have a 140 bp deletion knocking down the α, β, and γ isoforms and have no learning and memory comparisons to wild-type controls. Mice were trained at 2-4 months of age to discriminate an initial odour pair (A vs. B) to a criterion of 85% accuracy, then to a criterion of 85% accuracy on a second odour pair (C vs. D), and then to a criterion of 85% accuracy on reversal learning of the second odour pair, where the rewarded outcomes are switched (S+ becomes S- and vice versa). Secondly, we tested for overtraining effects by overtraining mice on the second odour pair for an extra 180 trials after 85% accuracy criterion before a reversal to study its effects on total errors in reversal. Our results found no significant memory performance differences between Nrxn1+/- and wildtype (C57BL/6J) littermates in the initial odour pair discrimination, second odour pair discrimination or reversal learning discrimination. We also observed no sex differences or interactions on total errors in these discriminations, as well as no effect of overtraining on any of the genotypes compared to mice that were not overtrained. Our investigations into individual learning differences using our models determined common response phases in learning styles during tasks. We used signal detection theory to examine these learning style patterns in the olfactometer based on four possible outcomes: hits, misses, false alarms (FA), and correct rejections (CR). Using these responses, we coded discrimination and reversal learning styles into four different learning phases, which we defined as Perseverance (Misses & FA), Responds None (Misses & CR), Responds All (FA & Hits), and Respond S+ (Hits & CR). These phases of reversal learning allow us to analyze individual differences and explain how mice perform operant reversal tasks within an olfactometer. Our reversal learning theory also showed that “Learning to Learn” performance increases in reversal learning tasks is the reduction of Perseveration and Responds None responses. Future studies should consider the effects of age on reversal learning to determine whether age affects cognitive flexibility in the Nrxn1+/− mouse model.
Open Access
Adapting Health Economic Evaluation Metrics to Incorporate Estimates of Environmental Impact: An Examination of Spinal Laminectomy and Fusion Procedures in Canada
(2025-08-29) Nsitem, Kelachi; No; Master of Science; Department of Community Health & Epidemiology; Not Applicable; na; Yes; Sean Christie; Mohammad Hajizadeh; Daniel Rainham; George Kephart
Climate change is an urgent threat to public health, yet healthcare contributes substantially to environmental damage. This thesis explores how environmental impacts can be incorporated into health economic evaluations to support sustainable healthcare decision-making. A narrative review synthesized literature on ecological economics, planetary health, and sustainable healthcare to identify key themes relevant to health technology assessment. An empirical analysis examined the environmental footprint of a common surgical procedure, using real-world data to estimate emissions and explore opportunities for reduction. While environmental costs were small relative to total healthcare costs, they revealed where emissions are concentrated, and which aspects of care may be more easily changed. Patient travel emerged as a key contributor and a target for low-disruption reductions. By combining conceptual insights with practical analysis, this work demonstrates how environmental costs can be integrated into healthcare evaluation frameworks, helping healthcare systems align service delivery with broader climate and sustainability goals.
Open Access
Digital Scribing: Applications of Accessible Hyper-Imaging in Architectural Design
(2025-08-26) Samuel, Beckley; Not Applicable; Master of Architecture; School of Architecture; Not Applicable; Joyce Hwang; Not Applicable; Huschang Pourian; Roger Mullin
This thesis explores the application of scanning technology to architectural scribing techniques using digital, analogue and hybrid workflows. The project investigates ishibadate a traditional Japanese footing technique as a case study for precise scribing of manufactured material to a natural surface. The thesis then looks for avenues where digital workflows could be useful in the manufacture of precisely scribed material in an architectural context.
Open Access
INVESTIGATING THE EFFECT OF CEMENT STABILIZATION ON A SLATE WASTE ROCK
(2025-08-30) Walker, Matthew; Not Applicable; Master of Applied Science; Department of Civil and Resource Engineering; Not Applicable; n/a; Not Applicable; Gordon Fenton; Rob Jamieson; Craig Lake
Acid-producing waste rock is a by-product of urban construction, and its environmental impact necessitates proper disposal. Cement solidification and stabilization is a technique to limit the effect of acid drainage leaching from waste rock material and consists of mixing the waste rock with a cementitious binder, followed by placement in a containment cell. This technique aims to reduce water flow through the material and to increase the pH/decrease effluent contaminant concentrations. Many test methods are available to assess the performance of the stabilized material. Humidity cell testing weathers the treated material over time by repeatedly exposing the stabilized mixture to cycles of air and water. Based on humidity cell testing performed, the cement stabilization was effective in neutralizing the pH of the effluent leachate and slowing the release of most contaminants. Notable exceptions were sulfur and sulfate, which were detected in higher concentrations in the binder treated samples.
Open Access
Numerical Simulations of a Simplified Aeroengine Bearing Chamber
(2025-08-30) Boudreau, Eric; Yes; Master of Applied Science; Department of Mechanical Engineering; Not Applicable; Dr. Sophia He; Not Applicable; Dr. Mohammad Saeedi; Dr. Dominic Groulx; Dr. Baafour Nyantekyi-Kwakye
This research presents a comparison of several numerical multiphase approaches used to study a simple bearing chamber. Oil film thickness and scavenge efficiency are the main indicators used to quantify performance, and the models are validated against published experimental data. The test case conditions are meant to represent the transitional flow regime, which is the point at which viscous forces overcome the gravitational forces in the film. This case is particularly challenging to resolve due to high rotational speeds and large gradients in the film thickness. A novel approach was developed which couples Discrete Phase Modelling (DPM) for oil droplets, Lagrangian Wall Film (LWF) for thin-films, and Volume of Fluid (VOF) for thick-films. The technique was then used to validate two additional bearing chamber configurations: a protruded vent and a covered ramp leading to the scavenge pipe
Open Access
Urban-Rural Divide: Investigation of Travel Patterns, Work Arrangement Choices, and Electric Vehicle Preferences in Nova Scotia
(2025-08-28) Ghani, Maisha; Not Applicable; Master of Applied Science; Department of Civil and Resource Engineering; Not Applicable; NA; Not Applicable; Dr. Lei Liu; Dr. Uday Vnekatadri; Dr. Ahsan Habib
This thesis addresses the long-standing urban-centric bias in transportation research by foregrounding the urban–rural divide as a critical dimension for sustainable and inclusive mobility planning in the post-pandemic era. Using data from the 2022–23 Nova Scotia Travel Activity (NovaTRAC) survey, conducted across diverse communities, it evaluates multiple sampling methods, civic address, landline, cellphone, and social media, to improve representation, especially among hard-to-reach rural households. The mixed-mode approach captures socio-demographic, behavioral, and attitudinal differences across regions, offering a comprehensive portrait of how Nova Scotians live, move, and work. A Hybrid Choice (HCM) framework integrates observed and latent factors to explain both choices and motivations. The analysis focuses on two domains: public electric vehicle charging location preferences, highlighting region-specific infrastructure needs, and post-pandemic work arrangements, showing how contextual and attitudinal factors influence decisions. Findings clarify spatial inequities and inform inclusive EV infrastructure planning, flexible work policies, and sustainable mobility strategies.
Open Access
Establishing a Spatio-Temporal Atlas of Gene Expression after Traumatic Spinal Cord Injury
(2025-08-29) Dauphinee, Laura M.; Not Applicable; Master of Science; Department of Medical Neuroscience; Received; n/a; Not Applicable; Sultan Darvesh; Adam Johnston; Carman Giacomantonio; Sean Christie
Traumatic spinal cord injury (tSCI) has no cure, and effective treatments will require targeting secondary injury mechanisms at specific times and locations. This demands understanding how gene expression changes across space and time. Previous transcriptomic studies lack spatial context due to tissue homogenization. To overcome this, spatial transcriptomics was applied to characterize spinal cord gene regulation after tSCI. Female Thy1-YFP mice (14–16 weeks) received moderate T12 contusion injuries and were sacrificed at 4 hours, 48 hours, and 7 days, with a naïve control. Coronal and longitudinal sections were analyzed using the 10x Genomics® Visium HD platform. Graph-based clustering, spatially variable gene detection, differential expression, cell-type deconvolution, and ligand-receptor analysis revealed region-specific patterns among ~16,500 genes. Neuronal and glial genes decreased, while transcription factors and immune-related genes increased. Egr1, Spp1, and Apoe showed dynamic spatiotemporal responses. Findings highlight spatial transcriptomics as a powerful tool to guide development of targeted SCI therapies.
Open Access
Validation and Application of a Needs-Based Complexity Case-Mix System for Community-Based Primary Health Care Planning and Research
(2025-08-29) McDougall, Erin (Beth); Not Applicable; Doctor of Philosophy; Department of Community Health & Epidemiology; Received; Dr. Robert Reid; Yes; Dr. Ruth Lavergne; Dr. Adrian MacKenzie; Dr. Emily Marshall; Erin Christian; Dr. George Kephart
Background: Canadian provinces are transforming their primary health care (PHC) systems by developing networks of resources at community and practice levels. This leaves provinces with the challenge of determining how to meaningfully measure the PHC needs of communities and practices. Currently, methods for systematically measuring PHC needs at community and practice levels are inadequate for PHC planning and are not routinely used. Objectives: The objectives of this research were to (1) operationalize and evaluate a complexity case-mix system to measure variation in PHC needs across practices and communities, and (2) apply the system to two areas of resource alignment relevant for PHC planning a) comparing the case-mix of PHC needs of patients unattached to a PHC provider with the attached population, and b) assessing if there are systematic differences in the case-mix of PHC needs between groups with different commuting patterns for PHC. Approach and Results: The setting of this research was Nova Scotia (NS), Canada. We adapted a previously developed case-mix approach for PHC, leveraging administrative data to classify Nova Scotians into a set of needs-based segments ranging from low to high complexity. We evaluated the complexity case-mix system against a set of criteria including consistency with research on what makes PHC needs complex, utility for PHC decision makers, and segment associations with healthcare use. Segments were consistent with research on what makes PHC needs complex, and decision makers found the NS complexity case-mix system to be useful, identifying multiple areas for application including evaluating PHC performance. Segments were further found to be predictive of healthcare costs and primary care costs. We then applied the case-mix system to the unattached patient centralized waitlist in NS and found that patients who are unattached to PHC have less complex needs than the attached population. We further rostered patients to providers and found variability in commuting for PHC by community, region, and need segment, with those who commute for PHC having less complex needs compared to those who do not commute. Impact: The results of this embedded research are enhancing the capacity to design and iteratively improve community PHC systems.
Open Access
Mi’kma’ki in Bloom: Wood-Splint Flowers: Art, Resistance, and Cultural Continuity
(2025-08-26) Clarke, Ava; Not Applicable; Master of Arts; Department of History; Not Applicable; n/a; Not Applicable; Dr. Jerry Bannister; Margaret Robinson; Dr. Lisa Binkley
Wood-splint flowers, an art form practiced by Mi’kmaw artist Madeline Knockwood in the late 1930s, represent a distinct and enduring art form in Mi’kma’ki (the traditional homeland of the Mi’kmaq) today by artists who continue the practice. Mi’kmaw artists continue to make these intricate flowers, sustaining Knockwood’s legacy and reinforcing the cultural significance of this art form. Examples of Knockwood’s wood-splint flowers can be found in museums and educational collections in Kjipuktuk (Halifax, Nova Scotia), underscoring their historical and contemporary significance. This thesis uses a material culture methodology to examine wood-splint flowers as a lens through which to understand Mi’kmaw artistic traditions, their connection to Mi’kmaw ways of knowing, the euro-settler/traveler souvenir economy, and the strategic use of commodity art as a counter to assimilation pressures. I argue that wood-splint flowers are a marker of Mi’kmaw cultural continuity, yet simultaneously, material evidence of adaptation, innovation, and the enduring human drive to honour creative traditions amidst social and economic changes.
Embargo
GROWTH RATE, ELEMENTAL AND BIOCHEMICAL COMPOSITION, AND SINKING DYNAMICS OF SMALL NANOPLANKTONIC DIATOMS: IMPLICATIONS FOR SEASONAL BIOGEOCHEMICAL CYCLING IN MARINE ECOSYSTEMS
(2025-08-28) Samarasinghe Gunasekara Liyanage , Ishari Nuwanthi; Not Applicable; Doctor of Philosophy; Department of Oceanography; Not Applicable; John Berges; Not Applicable; Anya Waite; Andrew Irwin; Christopher Algar; Zoe V. Finkel
Diatoms are a highly diverse group of phytoplankton that contribute approximately half of global marine primary production and span a wide size range from less than 3 μm to more than 1000 μm in diameter. To date, most studies have focused on medium-sized diatoms between 4 to several 10s of µm in diameter. There is accumulating evidence that small nano-sized diatoms (> 2 and <4 µm in diameter) are common members of phytoplankton communities. Laboratory experiments were conducted to quantify the growth rate, elemental (C: N: Si: P), and macromolecular (protein, carbohydrate, lipids, RNA, and DNA) composition of two nanoplanktonic diatoms, Minidiscus trioculatus (CCMP 501) and Minutocellus polymorphus (CCMP 496) in comparison to the slightly larger (~5 μm) Thalassiosira pseudonana (CCMP 1335), across a gradient of irradiance (5–800 μmol photons m⁻² s⁻¹) and temperature (5–25 °C). Results showed that carbon to nitrogen (C: N) ratios were not size-dependent, but C: P, N: P, and Si: N were consistently lower in the small nanoplanktonic diatoms. The low C: P and N: P in the small nanoplanktonic diatoms are correlated with elevated of DNA: C and DNA: P. Complementary year-round field sampling (2023-2024) of surface particulate organic matter (POM) from the Bedford Basin (44.69°N, 63.64°W) supported these findings, with the lower values of C: P and N: P and higher DNA: C in the smaller size fraction (0.4 - 3 μm) relative to a larger size fraction (3 -300 μm). There were pronounced seasonal variation in C: N: Si: P in both size fractions, with spring characterized by low C: N: P and high Si: C, suggesting diatom dominance in both size fractions in spring. Elevated RNA: DNA and RNA: protein ratios during spring further supported rapid diatom growth in Spring. To evaluate whether small nanoplanktonic diatoms can sink as rapidly as larger species, a set of sinking experiments were conducted comparing the rates of M. trioculatus and M. polymorphus with that of the ~13 μm diatom Thalassiosira weissflogii (CCMP1010). Sinking experiments revealed that small nanoplanktonic diatoms, especially when forming chains or aggregates, can sink at rates comparable to or exceeding those of larger diatoms. Sinking rates increased during stationary phase, likely due to physiological and morphological changes, though species-specific responses to light and aggregate structure moderated this effect. Integrated laboratory and field data reveal that small nanoplanktonic diatoms, characterized by distinct elemental stoichiometry (low C: P, N: P), elevated DNA content, and enhanced sinking potential during aggregation significantly influence marine nutrient cycling, carbon export efficiency, and food web dynamics over different seasons.