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Human activities have caused acidification of freshwater systems on a large scale resulting in reduced species diversity and ecological functioning in many lakes and streams. However, many naturally acidic freshwater systems have also been found, for instance in northern Sweden. In regions where such naturally acidic aquatic ecosystems have prevailed over evolutionary periods, species diversity and ecological functioning are not automatically impaired due to possible adaptation to the putatively adverse environmental conditions. I studied species diversity patterns and ecological functioning in anthropogenically acidified, naturally acidic, circumneutral, and limed streams to test the adaptation hypothesis and examine the ecological effects of variation in naturally acidic water chemistry. Species diversity was studied using benthic macroinvertebrates, while functioning was modelled using the decomposition rates of leaf litter. In accordance with the evolutionary species pool hypothesis, species richness was reduced more strongly in regions with anthropogenic than natural acidity when compared to circumneutral streams, supporting the adaptation hypothesis. In contrast, the patterns in ecological functioning along the pH-gradients did not differ between regions with anthropogenic and natural acidity, likely resulting from compensation: the biomass of tolerant taxa probably increased which thus rescued the loss in functioning otherwise mediated by the more sensitive taxa. Furthermore, the naturally variable acidic water chemistry clearly supported distinct macroinvertebrate assemblages, as was reflected in differing patterns of species diversity and ecological functioning. Such naturally acidic waters that were rich in dissolved organic carbon supported higher ecosystem process rates and lower species diversity than waters that contained little dissolved organic carbon. Upon liming naturally acidic streams microbial leaf decomposition increased, whereas shredding decreased along with changes in shredder abundances. The abundance of large caddisflies decreased, while the abundance of small stoneflies increased. The results suggest that various types of benthic macroinvertebrates with varying levels of adaptation and tolerance inhabited the hydrochemically variable naturally acidic streams. The distributions of macroinvertebrates in response to different pH levels and differences in acid quality and how these distributions translate into varying patterns of species diversity and ecological functioning are worthy of further investigation. This will likely improve our understanding of how such naturally acidic streams and their biota can be successfully managed.

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The risk of crude oil exposure to the early life stages (ELS) of fish is difficult to assess, given the complexity of the chemical composition of different oils. The aromatic portion of crude oil contains polycyclic aromatic hydrocarbons (PAH), which are known to be toxic. In 2004, an “effects-driven” fractionation research program was initiated in an attempt to better identify toxic constituents of two unique crude oils, Alaskan North Slope Crude (ANSC; medium-heavy crude) and Scotia Light (SCOT; light crude). The ANSC contained much more PAH than SCOT. These oils induced cytochrome P4501A1 (CYP1A) enzymes in juvenile rainbow trout (Oncorhynchus mykiss) and caused blue-sac disease (BSD) and mortality in larval Japanese medaka (Oryzias latipes). Four unique fractions (F1-F4) were produced from both oils via low temperature vacuum distillation. The F3 contained an array of unsubstituted and alkyl-PAH, and was responsible for most of the CYP1A induction and chronic toxicity associated with whole oil. Cold acetone extraction (CAE) of F3 produced 2 new sub-fractions (F3-1 and F3-2). The F3-1 was rich in alkyl-PAH, was a potent CYP1A inducer, and was chronically toxic to ELS of fish. The F3-1 was further separated into five more sub-fractions via normal phase HPLC (F3-1-1 – F3-1-5). Neither F3-1-1 nor F3-1-2 induced CYP1A or produced BSD, but F3-1-2 was lethal. The F3-1-3, 4, and 5 were all potent CYP1A inducers and were all chronically toxic. Induction of CYP1A proved to be an effective tool for tracing potentially toxic PAH throughout fractionation (Chapter 2), and sub-fractions rich in alkyl-PAH caused the most BSD and mortality (Chapter 3). Alkyl-homologues of phenanthrene, fluorene, naphthobenzothiophene (NBT), pyrene, and chrysene are perhaps the most toxic of the known constituents present in crude oil. The ANSC sub-fractions were more toxic than the SCOT ones, indicating that heavier crude oils with a higher proportion of intermediate-sized alkyl-PAH may be more toxic than lighter crude oils that are comprised of fewer of these compounds. / Thesis (Master, Biology) -- Queen's University, 2007-12-20 13:18:50.794 / This research was accomplished with funding assistance from the Nationmal Oceanic and Atmospheric Administration (NOAA), Petroleum Research Atlantic Canada (PRAC), Environment Canada, and the Department of Fisheries and Oceans.

I examined the distribution of stable isotope ratios of nitrogen $( delta sp{15}$N) and carbon $( delta sp{13}$C) in fish and aquatic invertebrates. Animals are enriched in $ delta sp{15}$N compared to their diet and I hypothesized that among-lake variation in the $ delta sp{15}$N of a top predator should reflect variation in the length of the food chain leading to it. A comparative study of a biomagnifying contaminant, mercury, confirmed that the presence or absence of certain key organisms such as pelagic forage fish and the crustacean Mysis relicta determined among-lake variation in mercury in lake trout, a top predator in the lakes. Mercury levels from the longest food chains where pelagic forage fish and Mysis were present were higher than those from the shortest food chains where these last two components were missing. This biogeographic variation in food chain length was correlated with variation in the $ delta sp{15}$N of trout. The use of $ delta sp{15}$N as a continuous, integrative measure of trophic position was further supported by its correlation to mercury in lake trout. However, such cross-system comparisons in $ delta sp{15}$N can be complicated by differences in $ delta sp{15}$N at the base of the food chain. Using large primary consumers (unionid mussels) as bio-indicators, I showed that $ delta sp{15}$N increases markedly with the human population in the lake watershed, an effect of the high $ delta sp{15}$N of human sewage. Correcting for this baseline variation in $ delta sp{15}$N, I reported that food chains leading up to nearshore fish species varied by about only one trophic level among the 35 lakes studied. A study of the $ delta sp{15}$N of coral reef and intertidal organisms collected along the coast of the the Carribean island of Barbados extended these patterns observed in lakes to coastal systems: baseline variation in $ delta sp{15}$N was related to human density on the adjacent watershed and within-site variation $ delta sp{15}$N

<p>Results from this study enables a better understanding of groundwater surface water interactions in the TMG, particularly regarding aquatic ecosystems. It has also highlighted the necessity to do proper impact assessments before proceeding with bulk abstraction from this important aquifer. The results also demonstrated the importance of differentiating between real groundwater and non-groundwater discharge contributions to surface hydrology and where these interface areas are located.</p>

Over the past two decades, Lake Winnipeg has been experiencing increasingly rapid eutrophication, and large cyanobacterial blooms now form in the North Basin in most years in late summer or fall. Cyanobacteria are considered a relatively poor food source compared with other phytoplankton, but the impacts of these blooms upon the primary consumers in the lake have not previously been researched. A microscopic analysis of whole water samples found cyanobacteria to be scarcely present in summer 2012, with nitrogen-fixing and non-fixing cyanobacteria comprising 11.2% and 8.4% of the basin-wide biovolume, respectively, and all but absent in fall. Gut content analysis of chironomids found that cyanobacteria made up an almost negligible part of their diet. Stable isotope analysis revealed that nitrogen-fixing cyanobacteria reduced phytoplankton δ15N values, and that this same reduction could be traced through the zooplankton, but not down to the sediments or chironomids.

The phytotoxicities of monensin, the 10:2 saturated fluorotelomer carboxylic acid (10:2 FTCA), and atrazine to freshwater macrophytes were investigated in three microcosm-based assessments. Both responses of plants grown as individuals in “cone-tainers” and those grown in mixed and monocultures were examined to permit comparison of the toxicological sensitivities of macrophytes under each planting design, and investigation of whether interactions between neighbours may modify plant response to an environmental contaminant. Exposures of monensin and the 10:2 FTCA at environmentally relevant concentrations were found to produce few significant effects in the higher aquatic plants across all growth conditions, thus direct comparisons of effective concentrations were not conducted. Significant differences between relative growth rates (RGR) of plant grown in assemblages versus individually indirectly indicate that over longer exposure durations toxicity may be underestimated using the individual “cone-tainer” method. RGRs and sensitivities of plants to atrazine were found to be in the same range across planting methods, demonstrating that responses of aquatic plants in the individual-test system reflected those observed in model populations and two-species communities. A lack of observed relations between plants in the mixed and monoculture tests, however, meant that the potential for modification of toxicity through plant interactions was not investigated.

This project examines the spatial relationships that exist between Winnipeg, Canada and Tokyo, Japan, with the intent to develop an understanding of the preciseness of the world. Different site-specific systemic conditions were used as critical tools to explore the implication of distinct design catalysts and inhibitors. I have concentrated on the relationships that exist between time and space, to identify and displace localized, momentary events that exist in one site to the other. Familiarities of my local surroundings were deliberately obscured to make explicit a heightened awareness of my position on the planet. This helps to facilitate discussions. I have created a space that is dissembled through abstract understandings of displaced elements in the environment. It is my intention for this space to be experienced in a different way each time we come across it, by shifting and changing ones perception of their character in the world.

Evolutionary history has been recognized as an important factor in studying ecological communities. Lake fish communities have had limited consideration from a community phylogenetics perspective and present the opportunity to include trophic interactions in the analysis. For the species under study, I used known phylogenies from the literature and genetic information to determine relative branch lengths and phylogenetic relationships by Bayesian inference. Using the resultant phylogenetic tree and fish community data, the phylogenetic community structure was determined for the lakes in the Manitoulin Island and LaCloche regions of Ontario, Canada. Evidence of phylogenetic structuring was found, particularly associated with piscivory, winter hypoxia tolerance, and thermal preferences for deep coldwater lakes. Although the majority of the lakes were weakly structured from a phylogenetic perspective, significant trends were nonetheless apparent; especially when further informed by examining species-specific trends, demonstrating that evolutionary history can play a role in structuring freshwater fish communities.