Landscape ecotoxicology is the study of dose-response relationships to toxicants and integrating environmental factors across a defined landscape. In this thesis, I contributed new knowledge to the field of landscape ecotoxicology by adapting analytical methods to assess spatial patterns of chemical exposure among different wildlife keystone species, quantify the relationships between contaminant sources and exposures, and quantify dose-response relationships across large landscapes. Currently, there are few landscape ecotoxicology tools available for quantifying geospatial patterns of environmental toxicology data. To address this gap, I adapted spatial and statistical methods and demonstrated how they can be used to 1) integrate data and assess spatial patterns of contaminant exposure; 2) assess spatial patterns of exposure to complex mixtures; and 3) examine dose-response patterns across landscapes. I developed fur Hg as a biomarker medium as a non-invasive biomonitoring tool in river otter (Lontra canadensis) and mink (Neovison vison) by developing conversion factors that can be used to estimate internal organ Hg from fur Hg, using a meta-regression approach. Based on these results, I suggest that the fur Hg screening guideline be reduced from 20 ug/g to 15 ug/g to be more conservative. I also quantified how the distribution of fur Hg changes across the pelt of river otters. Results from this study indicate that topcoat should be used for biomonitoring as it is less variable than the undercoat and samples should be taken from the forebody (head and legs) for the most accurate organ Hg estimation. Using biomarkers of exposure, I quantified the relationship between sources of Hg and factors that promote Hg bioaccumulation with dietary Hg from stomach contents and fur Hg to establish fur as a proxy for bioavailability of environmental Hg. I also assessed spatial dose-response patterns between fur Hg and fur cortisol using a geographically weighted regression (GWR). Based on these results I use my proposed fur screening guideline of 15 µg/g to categorize fur Hg exposures and demonstrate that at low exposures (<15 µg/g) in fur, Hg has a positive relationship with cortisol. Conversely, at high exposures (>15 µg/g) in fur, Hg has a negative relationship with cortisol. This research provides a field example of heterogeneous dose-response relationships. Finally, I assessed spatial patterns of complex metal exposures in a variety of biomonitoring datasets. I used normalization and transformation techniques to effectively combine datasets comprised of different species and life stages. I then used a spatial principal components analysis (sPCA) to exemplify clusters of complex exposures associated with oil and gas development in regions of Alberta, Canada. These advancements in the field of landscape ecotoxicology will help advance evidence-based long-term ecological monitoring programs.

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Over the last decade the development and use of nanomaterials (NMs) and nanoparticles (NPs) has increased at a great rate. As a result there is an ever increasing risk of exposing humans and wildlife to these potentially harmful materials. Titanium dioxide nanoparticles (TiO2 NPs) and carbon nanotubes (CNTs) are two of the most widely used NMs at present. Their potentially harmful effects on organisms and physicochemical properties have been investigated in a growing number of scientific studies. However understanding the level of risk they may pose is far from satisfactory. The present body of work has addressed various aspects of this field. In order to better quantify the fate of TiO2 NPs in the environment the methodology of measuring Ti from TiO2 NPs was improved using ICP-OES and single particle ICP-MS was demonstrated to provide the first steps towards characterising the nature of TiO2 NPs in liquid-phase media. The potential harm of TiO2 NPs and single walled carbon nanotubes (SWCNTs) to zebrafish was investigated in two separate studies. Little evidence of physiological toxicity was found and the only nano-scale effect of note was an increase in total glutathione of zebrafish exposed to TiO2 NPs. More subtle effects in reproductive studies were further investigated using the three-spined stickleback in a longer term investigation. Similarly to the zebrafish there was little evidence of any physiological disturbances and the well documented reproductive behaviour of the stickleback was not significantly altered as a result of TiO2 NP exposure. This body of work has added to the understanding of the potential toxic effects caused by exposure to both TiO2 NPs and SWCNTs. Improved methods for the detection and characterisation of TiO2 NPs have been demonstrated and the most sensitive tools for ecotoxicological assessments of NP toxicity have been elucidated.

This study involved the development and evaluation of a number of biomonitoring techniques for use with members of the Ulvaceae, Enteromorpha intestinalis (L.) Link, and Viva iactuca (L.). The techniques included both previously established ones and those which required development. The two main procedures developed for these algae were the neutral red retention technique (making use of a vital stain) and the ion leakage Health Index (based upon electrolyte leakage). Following optimisation both were used to produce quantitative structure-activity relationships (QSARs) for a series of n-alcohols using log Kow as the physicochemical parameter. The resultant QSARs were statistically indistinguishable with line equations of -0.88 log Kow + 2.87 and -0.95 log Kow + 2.83 respectively, with r values of 0.98, suggesting that both reflect the same non-specific narcotic effect on membrane integrity. However the neutral red retention technique was less useful than the Health Index with low reproducibility and is therefore unsuitable for use as an environmental biomonitor. The effects of other compounds with specific modes of action were established using the ion leakage technique, the high toxicity of the antifouling compound tributyltin being reflected in the Health Index. Further development of the ion leakage technique involved inductively coupled - plasma mass spectrometry (ICP/MS) in the identification of ions lost during leakage. Synergistic toxicity was investigated exposing the algae to UV light and anthracene, simulating photo-induced toxicity. No photo-induced toxicity was observed although UV exposure did reduce the Health Index. An environmental assessment was carried out for algae from clean sites and organically and inorganically polluted sites, comparing the Health Index with other measures of health and bioaccumulation data. A long term study of a clean site showed the algal Health Index to be influenced by seasonally dependent physical parameters, but reflected reduced health in algae exposed environmentally to organic pollutants. Algae exposed to long term heavy metal pollution in the Fal Estuary had 'normal',. Health Indices, however chlorophyll fluorescence induction techniques did highlight a reduced photosynthetic efficiency in these algae. The ion leakage technique has potentially a wide application in field and laboratory based biomonitoring and direct toxicity studies. Chlorophyll fluorescence analysis was also shown to be useful although it requires further investigation and evaluation.

The present study focused on methylmercury (MeHg) in emergent aquatic insects and spiders from human-made ponds. This dissertation addresses two main topics: (1) factors affecting variation in spider MeHg concentrations around human-made ponds and (2) the magnitude of MeHg transported out of human-made ponds by emergent aquatic insects (insect-mediated MeHg flux). Spiders were specifically targeted in this study because they have been proposed as sentinels of MeHg contamination (organism whose tissue concentrations reflect the level of MeHg in the environment). Spider MeHg concentrations were related to spider diet, size, and proximity to waterbody, but affected individual spider taxa differently. In a second study, I found that only "large" spiders within a taxa had tissue concentrations positively related to prey MeHg concentrations. These results indicate that the relationship between spider and prey MeHg could be size-dependent and that "large" spiders within a taxa may better reflect ambient MeHg contamination. Finally, I tested a conceptual model hypothesizing insect-mediated MeHg flux from human-made ponds is controlled by pond permanence and fish presence. In agreement with the conceptual model, insect-mediated MeHg flux from ponds was suppressed by the presence of fish, likely due to fish predation on emergent insect larvae. I found the mean aggregate MeHg flux was approximately 6 times higher from ponds without fish than from ponds with fish. The suppression of insect flux by fish was stronger for large insect taxa than small insect taxa. Results of this study indicate that community structure can influence the cross-system transport of contaminants, like MeHg, from ponds to terrestrial food webs.

<p dir="ltr">Aquatic ecosystems and their inhabitants are no strangers to stressors. Natural stressors like disease, competition, and predation have a near constant presence in these environments and are often accompanied by human-induced stressors like climate change and chemical contaminants. Chemical contaminants like pesticides are often found in aquatic systems located near agriculture and can have detrimental effects on wildlife. Although natural stressors and pesticides often occur at the same time, their combined interactions still require further investigation to understand, as some pesticides, like fungicides, are frequently under researched. Additionally, fungicides also are lacking in research pertaining to combined chemical stressors. Studying the interactive effects of combined stressors, whether natural or human-induced, is crucial for applying laboratory findings to natural environments.</p><p dir="ltr">Here, I conducted an outdoor mesocosm experiment and multiple laboratory experiments to broadly assess the interactive effects of the fungicide chlorothalonil. More specifically, I explored 1) the interactive effects of the herbicide atrazine and chlorothalonil on an aquatic community, 2) the interaction between chlorothalonil and predator-induced stress of three tadpole species, and 3) the impacts of chlorothalonil on amphibian predator-prey dynamics using tadpoles and larval salamanders. First, to test my hypothesis that atrazine and chlorothalonil will have combined interactions that negatively impact an aquatic community, I conducted a mesocosm experiment where I exposed an aquatic community to atrazine, chlorothalonil, and the combination of the two pesticides. I found that the two pesticides do hold the potential to interact in certain cases, but their main effects alone are often just as damaging, especially for chlorothalonil where an environmentally relevant concentration caused near total morality for bullfrog tadpoles.</p><p dir="ltr">Next, I conducted a laboratory experiment with tadpoles and caged predators exposed to a sublethal concentration of chlorothalonil to test my hypothesis that the combination of predator-induced stress and chlorothalonil will decrease tadpole survival and alter tadpole behavior. I found that chlorothalonil alters tadpole behavior by significantly reducing activity levels in all three study species. However, no evidence was found for the interaction of the two stressors decreasing survival.</p><p dir="ltr">Lastly, to test my hypothesis that the toxicity of chlorothalonil will reduce tadpole behavioral responses and thereby increase their predation risk, I conducted a laboratory experiment with free-swimming tadpoles as prey and larval tiger salamanders as predators, exposed to different combinations of chlorothalonil exposure for the prey or predator. I found no meaningful differences in survival curves for the different combinations of prey and predator, but leopard frog tadpole final survival was lower in the higher chlorothalonil dose treatment due to predation.</p><p dir="ltr">Overall, these studies have assisted in filling research gaps on fungicides and their impact on predator-prey dynamics and aquatic communities. This work provided insights into the direct impacts of the herbicide atrazine and the fungicide chlorothalonil on aquatic species, and their potential to interact with natural stressors, emphasizing the need to protect natural ecosystems from chemical stressors.</p>

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The Common tern (Sterna hirundo) is considered a sentinel wildlife species for monitoring mercury (Hg) and other contaminants within the St. Lawrence River Cornwall/Massena Areas of Concern (AOC). Here, I investigate the relationship between Hg bioaccumulation and diet using stable isotopes of carbon (δ13C) and nitrogen (δ15N) in adult and chick Common terns from three colonies along a 160 km transect of the upper St. Lawrence River. The foraging range of the colony furthest downstream (EMC) includes both the Massena and Cornwall AOC’s while the two upstream colonies (213 and Ice) are more removed from known point sources of Hg. I also sampled winter- and summer-grown breast feathers to compare diet and Hg exposure on the terns’ breeding ground vs. the terns’ wintering grounds. Hg exposure in summer-grown feathers was significantly higher than Hg exposure in winter grown feathers. Stable carbon (δ13C) and nitrogen (δ15N) isotopes revealed a switch from a marine-based diet during the winter months to a freshwater-based diet on the breeding grounds. Among colonies in summer-grown and chick feathers, the only significant difference in total mercury (THg) exposure was found in chick feathers where Hg was significantly lower at 213 than Ice – both of which are upstream from the AOC’s. However, THg was negatively correlated with δ13C in both winter and summer feathers, and the most parsimonious multi-regression model for winter and summer feathers indicated that δ13C explains 24 and 25% of the variation in Hg exposure, respectively. This suggests terns foraging offshore bioaccumulate more Hg than individuals foraging inshore or in freshwater (winter feathers), and that during the breeding period, terns foraging in pelagic habitats bioaccumulate more Hg than terns foraging in littoral habitats (summer feathers). For the upper St. Lawrence River, these results provide strong evidence that foraging habitat is more important than colony location in determining Hg exposure in a top trophic consumer. / Thesis (Master, Biology) -- Queen's University, 2013-06-01 19:35:59.665