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Recent Submissions

Access status: Open Access ,
THE APPLICATION OF PALEOLIMNOLOGY TO INFORM FRESHWATER MANAGEMENT: THE CASE OF URBAN LAKES IN HALIFAX REGIONAL MUNICIPALITY, NOVA SCOTIA, CANADA
(2026-04-28) Hipwell, Kathleen; Not Applicable; Master of Environmental Studies; School for Resource & Environmental Studies; Not Applicable; Dr. Josh Kurek; Yes; Dr. Alana Westwood; Dr. Andrew S. Medeiros
Watershed-scale stress from urbanization can negatively impact ecosystem services communities rely on. Yet, a lack of historical context for individual-lake conditions impedes management planning that promotes evidence-based restoration/remediation targets and the efficient allocation of resources. Halifax Regional Municipality (HRM) Nova Scotia, Canada, has hundreds of lakes that are increasingly influenced by residential development, and most lakes in the urban/suburban core are developed to some degree. Here, I assessed surface sediment subfossil chironomid assemblages (Diptera: Chironomidae) from 40 HRM lakes and used a development index to determine if there is a relationship between assemblage structure and watershed development level. Chironomid assemblages were analyzed to understand the broader context of urban influence and to identify lake-specific environmental stressors that influence assemblage structure with water quality parameters for a subset of 29 lakes. Through the additional biostratigraphic analysis of three lakes we used paleolimnology to fill the gap in long-term monitoring data and to infer the influence of watershed development on urban lakes (Chocolate Lake and Settle Lake lie in residentially developed watersheds, and Spider Lake is in an undeveloped watershed). I found that chironomid assemblages followed a productivity gradient with development level, and that conductivity and ions were the primary drivers explaining variation in surface sediment assemblages. In the two lakes in developed watersheds, shifts in chironomid assemblages over time reflected documented patterns of human disturbance and indicate increased productivity. In contrast, the lake in an undeveloped watershed has remained oligotrophic throughout its history. Our results could facilitate informed decisions related to restoration/remediation targets and assist in the planning and management of freshwater resources.
Access status: Open Access ,
The Marine Predation, Migration, and Habitat Use of Inner Bay of Fundy Atlantic Salmon (Salmo salar) Kelts
(2026-04-23) Brown, Caliyena; Not Applicable; Master of Science; Department of Biology; Not Applicable; Tommi Linnansaari; Not Applicable; Marc Trudel; Sarah Tuziak; Sarah Fortune; Robert Lennox
Atlantic salmon (Salmo salar) populations have declined across much of their range, and the inner Bay of Fundy (iBoF) population has experienced one of the most severe collapses in North America. Despite supplementation-based recovery efforts restoring juvenile freshwater abundance, the number of adults returning to spawning rivers remains critically low and repeat spawners are largely absent, indicating that poor marine survival is hindering population recovery. Using temperature-sensing acoustic transmitters, this thesis examines the marine predation, migration, and habitat use of captive-reared iBoF Atlantic salmon kelts (post-spawned adults) to better understand the marine ecology of this critical life stage. Chapter 2 evaluates the role of predation in kelt marine mortality. Predation was observed in ~ 37% of iBoF salmon kelts detected in the Bay of Fundy (BoF). Neither fish size (total length; m) nor fish sex significantly influenced predation risk, but distinct spatial and temporal patterns of predation were evident, with events occurring predominantly during late spring and summer in the outer BoF. Thermal signatures indicated that most predation events were attributable to mesothermic predators, with limited evidence of marine mammal predation. Chapter 3 characterizes marine migration and seasonal habitat use of iBoF salmon kelts within the BoF. Seasonal modelling revealed increased kelt presence in the middle and outer BoF during late spring and summer, with spatial use shifting across months and concentrating in regions previously identified as important marine habitat. Kelts exhibited variable movement patterns, including both prolonged residency within the BoF and streamlined exits into the Gulf of Maine. About one third of the kelts exited the Bay at least once, primarily in May and June. Collectively, these findings provide contemporary evidence that predation is a prominent driver of marine mortality for iBoF salmon kelts, and that both survival and marine movements vary across space and time. This work directly informs recovery planning for this endangered population, including improving understanding of factors influencing marine survival, refinement of hatchery release strategies, and progress towards identifying important marine habitat for iBoF salmon kelts.
Access status: Embargo ,
Genomic Characterization of Five Isolates of Blastocystis Subtype 7
(2026-04-27) Seaton, Gregory; No; Doctor of Philosophy; Department of Biochemistry & Molecular Biology; Not Applicable; Dr. Laura Wegener Parfrey; No; Dr. Claudio H. Slamovits; Dr. James M. Kramer; Dr. Morgan Langille; Dr. Andrew Roger
Blastocystis spp. are common, genetically diverse anaerobic colonizers of the gastrointestinal tracts of both humans and animals. Although they are traditionally regarded as parasites, their precise role in host health remains unclear, in part because cryptic genetic diversity is masked by morphological similarity among divergent lineages. Subtype 7 (ST7) contains several isolates (C, H, E, G and B) that have been shown to exhibit distinct phenotypic differences in experimental settings, suggesting genetic diversity within the subtype. This thesis presents a comparative genomic analysis of those five ST7 isolates, with a focus on genetic differences between the isolates. Genomes of four of the five isolates presented here are newly sequenced using a long-read-based assembly approach resulting in new genomic assemblies that are >98% complete and range from 19.8 (ST7C) to 20.2 (ST7G) Mbp in size and were found to be highly syntenic. Short-read data suggests these Blastocystis ST7 isolates are haploid. For two of the newly sequenced genomes, ST7C and ST7G, the assembly was complete enough to capture 8 and 9 complete chromosomes respectively. Through comparisons of shared syntenic scaffolds amongst isolates, 16 nuclear chromosomes could be hypothetically reconstructed in ST7C. Comparative analyses revealed clear evidence of genomic rearrangements in ST7G and ST7H relative to ST7C. Manual curation was used to create a high-quality gene annotation for ST7C that was propagated to the other genomes yielding 8625-8896 predicted genes per genome. The predicted gene set for ST7B contained 2593 more genes than a previously published genome analysis for this isolate. A pangenome analysis of the five isolates was conducted and a small (228) accessory genome was identified compared to a far larger core gene set (6198) shared by all the isolates. An abundance of endogenous viral elements belonging to the Midsized Eukaryotic Linear dsDNA (MELD) virus class were found and comparative analyses suggest that the MELD viruses first invaded the common ancestor of ST7 and ST6, and then greatly proliferated in the ST7 genomes. The analyses presented here offers insight into the genomic structure and differences between these Blastocystis ST7 isolates.
Access status: Open Access ,
Seismic Retrofit of Dry Precast Concrete Beam To Column Joint Using Shape Memory Alloy
(2026-04-27) Chen, DeZhen; Not Applicable; Master of Applied Science; Department of Civil and Resource Engineering; Not Applicable; N/A; Not Applicable; Pedram Sadeghian; Zoheir Farhat; Fadi Oudah
Superelastic shape memory alloy (SMA) is regarded as an ideal material for enhancing the seismic capacity of structures due to its superelasticity and self-centering properties. This research introduces and validates a new concept for the structural upgrade of seismically deficient precast concrete structures using SMA. The proposed approach establishes partial moment transfer at the beam-column joint, enabling the frame to partially resist lateral loads alongside the building's shear core. To achieve this, a novel device—termed the SMA Partial Moment Transfer (SMA-PMT) device—is developed and validated through experimental testing and analytical modeling using hybrid simulation. The research was executed in three stages, including model development, the experimental joint design and the experimental test. The discussion summarizes the behavior of the experimental joint specimens, focusing on joint moment capacity (yield moment), energy dissipation capabilities, and joint damage assessments. Recommendations for future research are also provided.
Access status: Open Access ,
Phase Change Materials and Storage Design for Pumped Thermal Energy Storage
(2026-04-24) VanLuxemborg, John; Not Applicable; Master of Applied Science; Department of Mechanical Engineering; Not Applicable; Dr. Michael Pegg; Not Applicable; Dr. Baafour Nyantekyi-Kwakye; Dr. Dominic Groulx
Pumped Thermal Energy Storage (PTES) is an emerging energy storage technology; a key component of the system is the Thermal Energy Storage (TES) unit. This thesis investigates the optimization of a multi-tube shell-and-tube TES unit through both numerical simulation and experimental material characterization to enhance thermal performance. A numerical model was developed to evaluate the performance of nine bare-tube configurations, varying from dual to oct-tube arrangements. The addition of longitudinal fins was explored to improve the charging time, while the impact of the length of the TES was also studied. In parallel to the initial numerical studies, potential Phase Change Materials (PCMs) were identified, and four selected materials, adipic acid, D-mannitol, hydroquinone, and LiNO3-LiOH (81:19 wt%), were characterized experimentally using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The numerical results indicated that the Oct-4F configuration delivered the most efficient charging performance and highest energy storage density. It was found that a system length between 0.50 m and 0.75 m balanced a sustained power output with maximal latent energy utilization. Experimentally, the synthesized LiNO3-LiOH (81:19 wt%) eutectic proved to be the most viable PCM, exhibiting excellent thermal stability with a melting temperature of 176.24 °C and a latent heat of fusion of 385.28 J/g. However, when the Oct-4F geometry was simulated using the LiNO3-LiOH (81:19 wt%) eutectic and Therminol 59 as the Heat Transfer Fluid (HTF), the system was unable to complete charging within the target eight-hour window. This was driven by the combination of the PCMs extremely high latent heat of fusion and the substantially lower specific heat capacity of the HTF, indicating that further geometric or operational optimizations are required to fully harness the material’s storage potential.
Access status: Open Access ,
Hospital Location Optimization Mixed-Integer Linear Programming Model for Timely Access to EVT Treatment
(2026-04-27) Baradaran-Noveiri, Borna; Not Applicable; Master of Applied Science; Department of Industrial Engineering; Not Applicable; na; Not Applicable; Dr. Peter Vanberkel; Dr. Adela Cora; Dr. Noreen Kamal
Timely access to endovascular thrombectomy (EVT) is critical for improving outcomes in acute ischemic stroke, yet access varies across Canada due to geographic and system-level constraints. This thesis develops a mixed-integer linear programming (MILP) model to optimize the designation of Comprehensive Stroke Centers (CSCs) within existing stroke systems. The objective is to minimize population-weighted time to EVT treatment while incorporating patient routing, inter-facility transfers, time-dependent EVT eligibility decay, and feasibility constraints. Population and travel-time data were used to model access at a granular geographic level, and candidate CSC hospitals were identified through a structured feasibility assessment. Results show that optimized CSC configurations can reduce treatment times by up to 25 minutes and increase the projected number of patients receiving EVT by 7.42%. This framework provides a data-driven approach to improving stroke system design and reducing disparities in EVT access across Canada.