Environmental and Life Sciences

Mixtures of metals occur in surface waters, toxicity of which has drawn world-wide attention due to their crucial role in both ecotoxicology and regulations. The present research was undertaken to study the acute toxicity of binary mixtures of Ni, Cu, Zn, and Cd to the freshwater organism, Daphnia magna. The experimental approach included single and binary metal toxicity tests based on the 48h acute toxicity bioassay of Environment Canada. The acute toxicity of single metals followed the order of Cd > Cu > Zn > Ni. Based on the calculated 48h EC50 value of single metals, a toxic unit (TU) approach was used to combine two metals in a binary mixture, in which 1TU was equal to the 48h EC50 value of a metal in single exposure. The toxicity of binary metal mixtures to D. magna followed the order of Cu-Cd > Cu-Zn > Zn-Cd > Cu-Ni > Zn-Ni > Cd-Ni, which demonstrated three types of toxicity (i.e., less than additive, additive, and greater additive). Predictions from additivity models (including concentration addition (CA) and independent action (IA) models), a generalized linear model (GLM), and a biotic-ligand-like model (BLM-like) were compared to the bioassay results. The CA and the RA models also predicted three types of toxicity of the binary metal mixtures (i.e., less than additive, additive, and greater than additive). However, the CA model mostly overestimated the toxicity of binary mixtures. Predictions from the GLM supported the inclusion of the interaction between two metals in a mixture to predict the toxicity of binary metal mixtures. The binary metal toxicity was also predicted using a BLM-like model based on the calculated concentrations of free ionic forms of the metals, affinity constants, and toxic potency of each metal. In this model, it was hypothesized that the toxicity of metal mixture is the result of competition of metals with Ca2+ at biotic ligands, which can lead to whole-body deficiency of Ca2+ in D. magna. The BLM-like model provided the toxic potency of single metals with the following order, Cu > Cd > Zn > Ni. Although the prediction of the BLM-like model was not in good agreement with the observed toxicity of binary metal mixtures, an overestimation of risk of mixture toxicity was obtained using this model, which could be promising for use in environmental risk assessment.

Author Keywords: biotic ligand model, concentration addition, Daphnia magna, independent action, metal toxicity, modeling

Wild populations are notoriously difficult to study due to confounding stochastic variables. This thesis tackles two components of investigating wild populations. The first examines the use of niche modeling to quantify macro-scale predator-prey relationships in canid populations across eastern North America, while the second examines range-wide molecular structure in Canada lynx. The goal of the first chapter is to quantify niche characteristics in a Canis hybrid zone of C. lupus, C. lycaon, and C. latrans to better understand the ecological differentiation of these species, and to assess the impacts of incorporating biotic interactions into species distribution models. The goal of the second chapter is to determine if DNA methylation, an epigenetic marker that modifies the structure of DNA, can be used to differentiate populations, and might be a signature of local adaptation. Our results indicated that canids across the hybrid zone in eastern North America exhibit low levels of genetic and ecological differentiation, and that the importance of biotic interactions are largely lost at large spatial scales. We also identified cryptic structure in methylation patterns in Canada lynx populations, which suggest signatures of local adaptation, and indicate the utility of DNA methylation as a marker for investigating adaptive divergence.

Author Keywords: Ecological Epigenetics, Ecological Genetics, SDM

The potential impacts of domestic wastewater (DWW) on the source of drinking water for the M'Chigeeng First Nation were monitored as part of the development of a Source Water Protection plan. During a period of continuous overflow of the Gaaming Wastewater Lagoon serving the community, the chemical tracers, caffeine and sucralose were tracked in West Bay with Passive Organic Chemical Integrative Samplers (POCIS). From the results, we speculated that DWI impacts could have been from three possible DWW sources. POCIS deployed above and below the thermocline indicated a higher mean sucralose concentration of 2.52 ± 1.83 ng/L in the hypolimnion of West Bay relative to mean epilimnetic sucralose concentrations of 0.56 ± 0.02 ng/L, suggesting possible wastewater percolation with an estimated time of travel of 61.5 days. Microbial loads of 200 CFU/100 ml E. coli from the lagoon overflow into Mill Creek decreased to 60 CFU/100 ml before entering West Bay. West Bay's wastewater assimilative capacity met Provincial Water Quality Objectives in the epilimnion and hypolimnion except for dissolved oxygen in the hypolimnion at 4.16 ± 1.86 mg/L, which is a threat to the onset of hypoxia for fish (i.e. <5 mg/L). Assimilative capacity results support a Fall lagoon discharge.

Author Keywords: caffeine, drinking water, Passive Organic Chemical Integrative Samplers (POCIS), sucralose, thermocline, wastewater

Soil and tree chemistry were measured across 15 limed sites that were established 14 to 37 years ago within the Sudbury barrens in Ontario, along with two unlimed pre-treatment condition reference sites and an unlimed remnant pine forest. Soil pH and base cation (calcium (Ca), magnesium (Mg), and potassium (K)) concentrations were elevated in surface organic [FH] horizons up to 37-years post limestone treatment. Limestone in the organic horizon was evident by higher Ca/Sr ratios (a good marker of dolomite) in younger sites. Base cation mass budgets were generally unable to account for the mass of added Ca and Mg. Sudbury is characterized by widespread metal contamination. Metal (copper (Cu), nickel (Ni), and lead (Pb)) concentrations were generally greatest within the FH horizon and unrelated to stand age. Copper and Ni concentrations in soil generally decreased with distance from the nearest smelter. Metal partitioning (Kd) in soil was most influenced by soil pH rather than organic matter suggesting that as liming effects fade over time metal availability may increase.

Author Keywords: Afforestation, Degraded, Limestone, nutrient, Space-for-time, Sudbury

In Canada, eastern flowering dogwood (Cornus florida L.) is an endangered tree that occurs only in the Carolinian forest of southern Ontario. Threats to this species include habitat fragmentation and the fungal pathogen dogwood anthracnose (Discula destructiva). I conducted a population genetic analysis using seven nuclear microsatellite markers to determine if fragmented populations are genetically isolated from one another and have low levels of genetic diversity. Genetic comparisons suggest on-going dispersal among sites and relatively high genetic diversity within most sites; however, smaller populations and younger trees were less genetically diverse. I also used linear mixed effects models to assess potential relationships between several ecological variables and the prevalence of dogwood anthracnose. Disease severity was higher in trees on shallow slopes and in larger trees; the latter also had higher likelihood of infection. Insights from this study will be important to incorporate into future management strategies.

Author Keywords: Cornus florida, Discula destructiva, dogwood anthracnose, Eastern flowering dogwood, endangered, population genetics

Decades of acidic deposition have depleted base cation pools in soil over large parts of eastern north America, including the Muskoka-Haliburton region of central Ontario. This region has also experienced a shift in forest species composition over the past 200 years, favouring sugar maple (Acer saccharum Marsh.) at the expense of species such as white pine (Pinus strobus L.) and eastern hemlock (Tsuga canadensis (L.) Carr.). This shift in species composition may have changed soil chemistry over time due to differences in nutrient and metal inputs in litterfall. An analysis of litterfall and soil chemistry was conducted for five tree species commonly found across central Ontario. Stands were established in the Haliburton Forest & Wild Life Reserve and were dominated by one of balsam fir (Abies balsamea (L.) Mill.), eastern hemlock, white pine, sugar maple, or yellow birch (Betula alleghaniensis Britt.). Analysis of mineral soil oxides suggested that these stands were established on similar parent material. Deciduous dominated stands (maple and birch) had greater litterfall mass compared with conifer stands (fir, hemlock, and pine), generally leading to greater macronutrient inputs to the soil. Elemental cycling through the organic horizons was more rapid in deciduous stands, with base cations having the shortest residence times. This suggests that a change from greater conifer dominance to mixed hardwood forests may lead to more rapid elemental cycling and alter the distribution of elements in soil. Forests in the region are typically mixed and the resulting differences in soil chemistry may influence model predictions of soil recovery from acidification. Laboratory leaching tests indicated that both stand type and the acidity of simulated rainwater inputs influenced soil solution chemistry, with deciduous stands generally having a greater buffering capacity than sites dominated by coniferous species. Changes in soil chemistry were examined for each stand type using the Very Simple Dynamic (VSD) biogeochemical model. Simulations showed that soil base saturation began to increase following lows reached around the year 2000, and similar patterns were observed for all stands. When sulphur (S) and nitrogen (N) deposition were held constant at present rates, soil base saturation recovery (toward pre-1900 levels) was marginal by 2100. With additional deposition reductions, further increases in base saturation were minor at all sites. In conjunction with additional deposition reductions, the elimination of future forest harvesting allowed for the greatest potential for recovery in all stands. Overall, these results suggest that changes in forest cover may influence soil chemistry over time, most notably in the organic soil horizons. However, forecasted recovery from acidification is expected to follow similar patterns among stands, since differences in soil chemistry were less significant in the mineral soil horizons which compose a greater proportion of the soil profile.

Author Keywords: base cation decline, forest harvesting, litterfall, mineral weathering, soil acidification, VSD model

The length of photoperiod can alter circadian rhythms and change fat depot mass whencombined with environmental temperatures below thermoneutral. To isolate photoperiod effects, we compared the effects of long and short photoperiod exposure at thermoneutrality in photoperiod sensitive, F1 generation adult male white-footed mice (P. leucopus). Mice were housed in long-day or short-day photoperiod conditions at thermoneutrality for 4 weeks. Short photoperiod decreased vWAT mass without changing body weight, scWAT or iBAT mass, or calorie consumption. Short photoperiod increased Adrβ3 and Lpl mRNA expression in vWAT with no change in Ucp1, Pgc1a or Hsl. vWAT Per1, Per2 and Nr1d1 mRNA expression were aligned to the onset of dark and food intake, while Bmal1 and Clock were misaligned. These findings suggest that short photoperiod per se can decrease visceral fat accumulation, without activating thermogenesis, reinforcing that environmental photoperiod should be considered when researching cause and prevention of obesity.

Author Keywords: adiposity, circadian rhythm, clock genes, obesity, Peromyscus, photoperiod

Lake of the Woods (LOW) is a large international waterbody which suffers from frequent and widespread algae blooms. Previous studies have highlighted the importance of the lake's largest tributary, the Rainy River (RR) and its significance in total phosphorus (TP) delivery to the LOW. Unfortunately, little is known about TP contributions from the RR and its tributaries within the Canadian portion of the watershed. This thesis examines patterns and sources of TP from four tributaries on the Canadian side of the lower RR region, two of which are predominantly natural, and two that are predominantly agricultural. Relationships between water quality parameters, land use and geologic characteristics were observed over a complete hydrologic year (Oct 1, 2018 - Sept 31, 2019), and through an intensive sampling campaign using a nested watershed approach during the spring high flow and summer low flow periods. Results revealed that TP and total suspended sediment (TSS) concentrations (>100 µg/L and >20 mg/L respectively), and loads (>20 kg/km2 and >3500 kg/km2, respectively), were greater at agricultural sites compared with natural sites (<65 µg/L TP and <15 mg/L TSS concentration, and <20 kg/km2 TP and <4000 kg/km2 TSS export). Total P, TSS, Fe, and Al were significantly positively correlated (R2= 0.26-0.59; p<0.05) and intensive sampling revealed that these relationships were strongest during the spring and at the agricultural sites (R2= 0.73-0.98; p<0.05). In contrast, the summer intensive sampling revealed that TP and redox sensitive Fe were significantly correlated (R2= 0.72; p<0.005), whereas redox insensitive Al and TSS were not, suggesting TP may be sourced via redox processes in the summer due to favourable hydrologic conditions. This was observed not only at sites with high wetland influence, but also at sites with more agricultural presence suggesting that redox sourced TP may also originate from mineral stream bed sediment during low flow periods. This research suggested two primary TP sources in the lower RR region: erosion in the spring, and redox processes (internal release) in the summer. It is recommended that intensive monitoring continue in Canada, and further research be conducted to fully understand the significance of internal P release in the tributaries.

Author Keywords: erosion, land use, nutrients, particulates, redox, water quality

In this study we seek to better understand the potential effects of short-term (5-year) N fertilization on jack pine forest biogeochemistry, vascular plant community composition and to project a temporal endpoint of nitrogen leaching below the major rooting zone. Aqueous ammonium nitrate (NH4NO3) was applied above the forest canopy across five treatment plots (20 x 80 m) four times annually. The experimental deposition gradient followed those known for localized areas around the major open pit operations at 0, 5, 10, 15, 20 and 25 kg N ha-1 yr-1 over a five-year period (2011 – 2015). Nitrate recovery in throughfall was significantly higher than NH4+ (p < 0.05), indicating canopy NH4+ immobilization. There was a strong treatment effect (p < 0.05) of N on the epiphytic lichen thalli concentrations of Hypogymnia physodes and Evernia mesomorpha after five years. The canopy appeared to approach saturation at the highest deposition load (25 kg N ha-1 yr-1) during the fifth year of N additions as most N added above the canopy was accounted for in throughfall and stemflow. The non-vascular (lichen and moss) vegetation pool above the forest floor was the largest receptor of N as cryptogam foliar and thalli N concentrations showed a significant treatment effect (p < 0.05). Nitrogen in decomposing litter (25 kg N ha-1 yr-1) remained immobilized after five years, while treatments ≤ 20 kg N ha-1 yr-1 started to mobilize. Understory vascular plant cover expansion was muted when deposition was ≥ 10 kg N ha-1 yr-1. Finally, modeling suggests the forest may not leach N below the rooting zone until around 50 years after chronic addition begin (25 kg N ha-1 yr-1). The modeling results are consistent with empirical data from a high exposure (~20 - 25 kg N ha-1 yr-1) jack pine site approximately 12 km west of the experimental site that has not yet experienced N leaching.

Author Keywords: Biogeochemistry, Canopy, Deposition, Jack Pine, Nitrogen, Understory

I examined Bank Swallow (Riparia riparia) colony persistence and occupancy, in lakeshore, river and man-made aggregate pit habitat. Habitat persistence was highest on the lakeshore and lowest in aggregate pits, likely due to annual removal and relocation of aggregate resources. Bank Swallow colonies in aggregate pit sites were more likely to persist if a colony was larger or if burrows were located higher on the nesting face. I also compared nest productivity and health factors of Bank Swallows in lakeshore and aggregate pit habitats. While clutch size was the same in both habitat types, the number of fledglings from successfully hatched nests was significantly higher in aggregate pit sites than from lakeshore sites. Mass of fledgling Bank Swallows did not differ significantly between habitat types, however mass of adults from aggregate pits decreased significantly over the nesting season. Parasite loads on fledgling Bank Swallows were significantly lower in aggregate pits than in lakeshore sites. According to these indicators, aggregate pits appear to provide equivalent or higher quality habitat for Bank Swallows than the natural lakeshore sites, making them adequate and potentially key for this species' recovery. Aggregate pit operators can manage for swallows by (1) creating longer, taller faces to attract birds and decrease predation, and (2) supplementing their habitat with water sources to encourage food availability.

Author Keywords: Aerial insectivore, aggregate pits, Bank Swallow, colony persistence, ectoparasites, substitute habitat