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I investigated the climate vulnerability of a cold-water salmonid by observing the upper thermal tolerance of brook trout (Salvelinus fontinalis) across multiple life stages. Using hatchery- and wild-ancestry fish, I assessed variation in thermal tolerances and carryover effects within and among brook trout life stages and populations that were reared under varying winter thermal regimes as embryos. Embryonic, fry, and gravid adult upper thermal tolerance were tested via CTmax. Warm acclimation was associated with an increase in embryonic upper thermal tolerance. CTmax variability was markedly higher in embryos than juvenile or adult salmonids. Effects of thermal incubation treatments varied by life stage, with incubation temperature and life stage both influencing body size and thermal tolerance. Collectively, these results suggest that brook trout only exhibit short-term carryover effects from thermal stressors during embryo incubation, with no lasting effects on phenotype beyond the first few months (10 weeks) after hatch.

Author Keywords: acclimation response, climate change, ontogeny, salmonid, stress, thermal plasticity

Although stormwater management ponds (SWMPs) are frequently used to mitigate flooding in urban areas, we still do not fully understand how these systems impact water quality in a watershed. Currently, most research focuses on the effectiveness of SWMPs to retain nutrients during high flows, even though there is potential for internal nutrient releases to occur in these systems during low flows. To investigate if SWMPs act as nutrient sources or sinks during low flow conditions, we analyzed how sewershed characteristics, pond properties, and hydrological and limnological factors influenced nutrient dynamics and stoichiometry in 10 SWMPs. Our study ponds were located in Peterborough, Whitby, and Richmond Hill, which are urbanized municipalities in southern Ontario, Canada. During October 2010 to 2011, we took monthly measurements of various carbon (C), nitrogen (N), and phosphorus (P) forms. We collected samples in the inlets, permanent pools, and outlets to determine any changes in concentrations, loads, and stoichiometric ratios into and out of the ponds. At the time of sampling, we also measured a variety of hydrological and limnological parameters. Our findings indicate that more urbanized sewersheds with higher drainage densities tend to have higher inflowing particulate and dissolved nutrient loads. In addition, we found that pond properties such as depth, length-to-width ratio, volume, and age differentially influence the retention of particulate and dissolved C, N, and P forms. Influential hydrological and limnological factors were antecedent moisture conditions, season, and thermal stratification. We found higher particulate P concentrations near the sediments when the catchments were drier and the ponds were ice-free and stratified. As well, we found higher outflowing stoichiometric ratios for DOC:TDN and DOC:TDP. This indicates an enrichment of C compared to N and P and suggests biogeochemical processes may be occurring in SWMPs. Overall, our results demonstrate that SWMPs are complex aquatic systems, and we need to consider biogeochemical processes in our design and maintenance activities, so that the effectiveness of SWMPs is not compromised during low flow conditions as a result of internal nutrient releases.

Author Keywords: Carbon, Nitrogen, Phosphorus, Urban biogeochemical cycling, Urban stormwater pond

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.

Low-density urbanism is ubiquitous in the industrialized world, with suburbs and sprawling urban zones like the American Northeastern Seaboard being classified as such. Due to outsized environmental impacts and perceived unsustainability, this settlement pattern is often maligned. As one of the few prominent examples of agrarian-based low-density urbanism, the ancient Maya can provide a much-needed case study on the sustainability of low-density urbanism. Therefore, a thorough assessment of the universality of low-density urbanism among the ancient Maya is warranted. Maps of 11 Maya sites were collected from published sources, digitized, and used to calculate household group densities. No significant difference was observed between Classic and Postclassic sites, but sites in the northern Lowlands were significantly denser than those in the southern Lowlands. Additionally, no significant inverse correlation was found between site density and area, which would be expected if low-density urbanism was universal among the ancient Maya.

Author Keywords: Household Archaeology, Low-Density Urbanism, Maya, Settlement Archaeology

Cadmium is a toxic metal that has detrimental effects on blood vessel development and function. To examine the effect of varying concentrations of cadmium on angiogenesis, two in vitro assays were used. First, developing yolk sac blood vessels were studied in gestation day 8 mouse embryos exposed to medium alone, 1.25, or 1.75 μM cadmium chloride (CdCl2). Embryos exposed to 1.25 μM cadmium experienced a significant increase in the number of vessels formed; however, they were smaller in size. Vessel morphology and signalling pathways were also investigated using the mouse aortic ring assay, with exposures of 0.0, 0.5, 1.0, 5.0, or 10.0 μM CdCl2. Samples exposed to 10 μM experienced a significant increase in vessel length. However, no significant differences in phosphorylated PTEN and AKT were observed. The results of this study suggest that low levels of cadmium may disrupt angiogenesis, particularly the development of the embryonic vasculature in the yolk sac.

Author Keywords: Angiogenesis, Cadmium, Embryonic Development, Teratogenicity, Vascular Development, Vasculogenesis

Animals are essential to freshwater biogeochemistry and productivity. Through their excretion, aquatic consumers release bioavailable nutrients and carbon that can vary with animal taxonomic rank, trophic position, and abiotic factors such as light and nutrient supply. In fresh waters, light and nutrient supply is often modulated by dissolved organic matter (DOM), a "murky" component in the water that gives it a brown color and that may indirectly affect animal nutrient and carbon excretion. Additionally, contaminants can impact animal physiology, altering metabolism and inducing stress, further affecting nutrient and contaminant excretion. The size and structure of the ecosystem, including community composition and biomass, can also impact the contribution of aquatic animals to the elemental pool. To understand these dynamics, I examined animal‐mediated elemental cycling in freshwater ecosystems across gradients of DOM concentration and composition and under contaminant exposure. I tested fish and invertebrate nitrogen, phosphorus, and DOM excretion across trophic positions during two sampling events in Lake Erie and in naturally DOM-variable streams and lakes. I also investigated the effects of chronic exposure to silver nanoparticles (AgNP) under environmentally relevant conditions on fish nutrient and silver (Ag) release. I found that aquatic animals can be a substantial nutrient contributor to the nutrient pool, particularly when their population biomass is high and ambient nutrient concentrations are low. I also detected nonlinear relationships between animal nutrient excretion and DOM characteristics that varied with taxonomic rank and trophic position and that dampened at larger ecological scales. Importantly, I identified several fish DOM excretion signatures that differed relative to ambient DOM and reported the first fish Ag excretion rates under AgNPs exposure. My results underscore the context-dependency and variability inherent in animal-mediated elemental cycling, highlighting the critical role of animals as both modifiers and conduits of nutrients, DOM, and contaminants in aquatic ecosystems.

Author Keywords: carbon, consumer-nutrient driven dynamics, ecological stoichiometry, nitrogen, phosphorus, silver nanoparticles

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

The ancient Maya utilized aspects of their landscape within their religious rituals and ceremonies, including caves. The study of ritual cave use is known as Maya cave archaeology and archaeologists in this subfield suggest that all holes in the earth, be it natural or man-made were viewed as ritually significant spaces to the ancient Maya (Brady and Layco 2018). This thesis analyzes the mortuary pattern of a chultun in relation to natural cave rituals and/or burials to determine if both types of subterranean spaces functioned in ritually similar ways. Through excavation of a dual-chambered chultun at the site of Ka'kabish, this research established a parallel pattern between burials found in natural caves and the burials within a chultun/artificial cave. In so doing, this thesis provides much needed data in support of applying Maya cave archaeology theories and practices in the excavation and study of ancient Maya chultuns.

Author Keywords: Belize, cave burials, chultuns, Maya archaeology, Maya cave archaeology, mortuary archaeology

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.