Environmental science

The detection of ciguatoxins (CTXs) in biological samples is challenging due to their low concentrations, the presence of various congeners, and the absence of standardized methods. This study uses high resolution mass spectrometry (HRMS) with P-CTX-3B as a reference standard. The protonated molecules ([M+H]+) were most prevalent, especially when acetonitrile/water was utilized, providing enhanced sensitivity. Optimized collision energies of 15 eV for protonated molecules and flow rates of 10 µl/min enhance sensitivity and peak intensities, respectively. Acetonitrile/water (ACN/H2O) is recommended as the primary solvent for HRMS method, an aspect underexplored in existing literature. The detection of CTX-3B in fish tissue samples proved to be challenging, caused by variations in ion peak intensities and matrix effects, requiring a deeper exploration of the impact of complex matrices on CTX detection. The study emphasizes the need for a reliable internal standard to mitigate these effects and highlights the ongoing challenge of developing a rapid, simple, and sensitive detection method. The study's specific focus on the P-CTX-3B analogue significantly contributes to methodology development for this congener, serving as a foundational step in understanding and detecting CTX. Despite notable progress, the study acknowledges the absence of an ideal assay, outlining key challenges for future research on ciguatera analysis. It underscores the continuous necessity for method reevaluation, testing, and the broader goal of establishing a more clarified and rugged method for the identification of CTX in fish.

Author Keywords: Analytical Chemistry, Ciguatera Fish Poisoning, Ciguatoxin, High-Resolution Mass Spectrometry, Optimization, P-CTX-3B

Northern flying squirrels (NFS) are mycophagous specialists (fungi-dominated diet) thatmay be displaced with southern flying squirrel (SFS) range expansion, thereby limiting fungal dispersal in forest communities. To understand the implications of squirrel species turnover on mycophagy, we investigated the home ranges of both flying squirrel species who are living in stable sympatry. We found no significant difference in home range sizes and identified spatial overlap between the two species. Through habitat selection ratios we found SFS were strongly selecting for deciduous-dominated habitats more than NFS. Lastly, we conducted microscopy on flying squirrel scat and found NFS were eating more fungi than SFS. We conclude that the squirrels are sharing the same habitat landscape but are finding ways to partition the habitat accordingly to allow for sympatry. SFS may contribute to the spore-dispersal cycle similarly to their northern counterpart through moderate fungus consumption and large home range sizes.

Author Keywords: diet, flying squirrels, Glaucomys, home range, mycophagy, sympatry

The Wabigoon River is known for an historic mercury (Hg) pollution source, caused by a chlor-alkali facility operating in the 1960s. As legacy Hg contamination continues to cause serious adverse health effects to the local communities living in the Wabigoon River region, it is imperative to undertake additional research to understand the deposition and transport of historical mercury in this system and more importantly, its conversion into methylmercury (MMHg) which renders it bioavailable for ongoing bioaccumulation. The aim of this dissertation was to evaluate the transport and accumulation of Hg species by doing a spatial and temporal analysis of concentrations of mercury and methylmercury along the Wabigoon River, as well as assessing rates of methylation and demethylation, identifying areas of higher methylmercury production. Results show that locations downstream from the pollution source still show elevated mercury concentrations, with levels at least five times higher in water and up to 134 times higher in sediments compared to background levels. Among selected study sites, the Hydroelectric dam, the Wabigoon Rapids wetland and Clay Lake were identified to have high capacity for methylmercury production in the system, with notably Clay Lake presenting a higher potential for methylmercury accumulation due to the observed lower methylmercury demethylation rate. Furthermore, the impact of wetting and drying cycles on Hg methylation in riverbed and wetland locations within the Wabigoon River system was investigated through a laboratory simulation. Findings indicated increased susceptibility of riverbed locations to wetting and drying cycles.

Author Keywords: Demethylation, Mercury, Methylation, Methylmercury, Wabigoon River

Eutrophication is an ongoing global problem and agriculture is an important non-point source of nutrient loading. Specifically, nitrogen (N) and phosphorus (P) losses from agricultural landscapes continue to drive water quality issues. In southern Ontario, agriculture has intensified in recent decades, with major expansions of cash crop production and extensive tile drainage (TD). Through intensive monitoring of 12 tile outlets draining operational fields under the conventional corn-soybean-wheat rotation, this study examined differences in measured and volume-weighted total P, total N, and nitrate-N concentrations and loads over 28 months (October 2020- April 2023) amongst crop covers and between growing (GS; May – September) and non-growing seasons (NGS; October – April). Nitrogen concentrations (i.e., TN and NO3-N) in TD eluent were consistently high both between seasons and were found to be significantly highest from winter wheat (WW) fields in the NGS, and corn fields in the GS. Volume-weighted TP concentrations were not significantly different either amongst crop covers or between seasons, although TP losses tended to be highest from the cover crop (CC) fields in the NGS. Differences in N and P losses between years and amongst crop covers were attributed to differences in legacy soil nutrients, the establishment and decomposition of over-winter cover crops, and physical soil properties. The results of this study can inform agricultural management by addressing the urgent need for improved information around the relationship between agricultural practices and nutrient losses, especially in the NGS.

Author Keywords: Best management practices, Crop rotation, Over-winter cover crops, Seasonality, Tile drainage, Water quality

Glyphosate burndown and tillage, followed by the cultivation of cash crops, are frequently used techniques in LUC from perennial cropping systems (PS) to annual cropping systems (AS). Agricultural LUC can result in the loss of soil nitrogen (N) via emission of nitrous oxide (N2O), a potent greenhouse gas (GHG). The purpose of this thesis is to investigate the short-term impacts of agricultural LUC from PS to AS on soil health parameters and the nitrogen (N)-cycling bacterial communities responsible for nitrification and denitrification processes that result in the emission of N2O. The study field site was in Stone Mills, Ontario and comprised of four fields: two annual cropping systems were regularly cultivated for cash crops (AS), and two perennial cropping systems had not been cultivated for cash crops for over 50 years (PS). One PS was left intact while the other PS was subjected to LUC (converted system [CS]) from PS to AS within the study period. The results of this study indicate that PS promotes soil health, as illustrated through higher soil organic matter % (2.3 ± 0.2 %), beta-glucosidase activity (0.41 ± 0.04 mmol g-1 dry soil h-1), and N-acetylglucosaminidase activity (0.18 ± 0.03 mmol g-1 dry soil h-1). The PS soils exhibited higher nitrifier (6.0  0.3 log10 copies per g dry soil) and denitrifier (nirS, nirK and nosZI: 7.8  0.05, 8.1  0.1 and 5.0  0.1 log10 copies per g dry soil, respectively) gene abundances compared to AS (amoA, nirS, nirK and nosZI: 5.7  0.1, 7.7  0.04, 7.9  0.1 and 4.8  0.1 log10 copies per g dry soil, respectively). Moreover, LUC from PS to AS deteriorated soil health parameters and significantly decreased the nosZI/16S rRNA gene ratio, leading to potential N loss through N2O emissions. A laboratory incubation study revealed that the use of N-containing fertilizer in conjunction with easily metabolized C cumulatively resulted in 64.2% increase in N2O and 42.1% increase in CO2 fluxes in AS soils compared to PS soils. The AS soils also produced 69.8% more N2O and 13.4% more CO2 when compared to CS soils. The results suggest that the availability of C and N promote R-strategists, leading to increased production of CO2 and N2O. Additionally, results also suggest that LUC mediates fluxes depending on resource availability. The findings of this research demonstrate the significance of LUC in shaping N-cycling microbial communities and GHG emissions, emphasizing the importance of transitioning towards less intensive management practices to ensure the long-term sustainability of the agri-food system.

Author Keywords: annual, denitrification, greenhouse gas, laboratory incubation, nitrification, perennial

Advanced generation/backcrossed (non-F1) hybrids can be challenging to identify when their traits are similar to those of parental taxa, F1 hybrids, or both. This is particularly evident in the North American hybrid zone involving Typha latifolia, T. angustifolia, F1 T. × glauca and non-F1 hybrids. Cattails are challenging to differentiate based on gross morphological characteristics. Microscopic characteristics in female inflorescences have not been previously studied to differentiate parental taxa from non-F1 hybrids. To investigate whether researchers can use microscopic floret and bracteole characteristics for taxonomic identification, I compared pistillate flower length, bracteole length and width, and bracteole colour among taxa. I found that floret and bracteole characteristics can be useful for identifying T. latifolia but cannot accurately differentiate T. angustifolia and F1 T. × glauca from non-F1 hybrids. Further, a flowering bias can lead to the underestimation of the frequency of T. latifolia when using floral characters to examine the relative abundance of cattail taxa.

Author Keywords: advanced-generation hybrids, backcrossed hybrids, invasive species, morphology, species identification, Typha spp.

Phosphorus is the growth-limiting nutrient in freshwater environments. Dissolved organic phosphorus (DOP) refers to phosphorus within dissolved organic matter (DOM). Much of DOP is bioavailable, but it is poorly understood due to its complexity. This thesis explores the export DOP to Lake Erie from its tributaries, by investigating its speciation and concentration seasonally through weekly sampling of two tributaries and spatially across a river to lake transect. The rivermouth was a site of rapid transition, with lower concentrations of DOP in the lake than in the river and a greater proportion of P as DOP in the lake. Phosphomonoesters and aromatic DOM were coupled in the medium-sized Grand River, but not in the Upper Great Lakes-influenced Detroit River. Phosphodiesters and highly processed DOM were coupled in the Detroit River, but only during periods of low terrestrial inputs. Finally, we found that DOP is a large contributor to tributary phosphorus exports.

Author Keywords: dissolved organic matter, dissolved organic phosphorus, enzymatic hydrolysis, Lake Erie, nutrient export, rivermouth

Wetlands are highly susceptible to the invasion of invasive species. The invasive hybrid cattail (Typha × glauca) is prevalent in the southeastern Prairie Pothole Region (PPR) wetlands. However, concerns arise about its recent proliferation in the northwestern PPR without maternal T. angustifolia. To determine taxonomic distribution, I used species-specific PCR-RFLP and microsatellite markers for genotyping 245 samples from 50 northwest PPR sites. I found 75% T. latifolia, 7% T. angustifolia, 16% T. × glauca, and 2% backcrossed or advanced-generation hybrids. F1 T. × glauca has expanded in western PPR without its mother species, and the low occurrence of later-generation hybrids indicates their recent range expansion. Additionally, T. angustifolia offspring make fewer hybrids, which suggests that reproductive barriers may limit hybridization between parental species. This study highlights the vulnerability of prairies to cryptic invasions by Typha hybrids, and early detection of invasive species is a critical factor in wetland management success.

Agricultural and urban land uses have been linked to the recent resurgence of eutrophication and salinization issues in the lower Great Lakes. This thesis examined the relationship between watershed land use and stream nitrate-nitrogen (NO3-N), total phosphorus (TP), and chloride (Cl) concentrations across southern Ontario. Using a self-organizing map analysis, the watersheds were classified into eight distinct spatial clusters, representing four agricultural, two urban, and two natural clusters. Agricultural clusters under intensive row crop agriculture exhibited NO3-N and TP concentrations up to twelve and five times higher, respectively, than the most natural-dominated cluster. Urban clusters had Cl concentrations up to nine times greater than the natural-dominated clusters. Three agricultural land use practices, namely continuous corn-soybean rotation, synthetic fertilizer application, and tile drainage, were positively correlated with stream NO3-N concentrations, whereas Cl concentrations increased with urban area and human population density. This thesis also characterized sampling trends of the provincial stream water quality monitoring program and found that sampling frequency has declined since the mid-1990s, while current sites are monitored almost exclusively during the ice-free period. Sampling year-round is critical to capture seasonal variations in NO3-N and Cl, while sampling across a full range of flow conditions is important for describing TP. Exclusion of sampling sites in close proximity of downstream municipal wastewater treatment plants and greenhouses can help isolate and better understand water quality impacts of non-point sources. Although intensive agricultural watersheds in southwestern Ontario draining into Lake Erie remain a priority for research and management, regions experiencing row crop expansion such as along the northern shore of Lake Ontario as well as rapidly urbanizing areas require further attention as these land use shifts will likely increase stream NO3-N and Cl concentrations, placing further pressure on water resources in the lower Great Lakes.

Author Keywords: Chloride, Nitrogen, Phosphorus, Self-organizing map, Southern Ontario, Water quality

In this study, twenty lake catchments surrounding Iqaluit, Baffin Island, were assessed for trace element concentrations (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, THg, V, Zn) in lake water, catchment soil, lake sediment, and moss (Hylocomium splendens). Additionally, the sources of each trace element were determined through the positive matrix factorization (PMF) model and enrichment factors (only in moss). Geogenic trace elements had the highest median concentrations (Fe>Al>Mn) throughout the study media and across the study catchments. Anthropogenic trace elements had the lowest median concentrations (Pb>As>Cd>THg) across the lake catchments, which were generally several orders of magnitude lower compared to geogenic elements. The PMF model identified trace elements associated with geogenic or anthropogenic sources, i.e., THg (47%), Cd (40%), Zn (34%), and Al (27%) were identified as originating from industrial emission sources deposited onto lakes because they accounted for a large proportion within the model.

Author Keywords: Arctic lake catchments, Biomonitoring, Enrichment factors, Positive matrix factorization model, Trace elements, Water chemistry