Historical Deposition and Microbial Redox Cycling of Mercury in Lake Sediments from the Hudson Bay Lowlands, Ontario, Canada

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dc.contributor.authorBrazeau, Michelle
dc.date.accessioned2012-04-17T18:52:08Z
dc.date.available2012-04-17T18:52:08Z
dc.date.created2012
dc.date.issued2012
dc.identifier.urihttp://hdl.handle.net/10393/22722
dc.identifier.urihttp://dx.doi.org/10.20381/ruor-5597
dc.description.abstractThe repercussions of climate change are felt worldwide, but Arctic and subarctic regions, where climate warming is expected to be amplified, are especially vulnerable. An episode of mass fish mortality in the Sutton River in the Hudson Bay Lowlands (HBL) of Northern Ontario has elicited the interest of the scientific community. Several lakes were sampled over three years in an effort to better understand and document the changes that may be occurring in these lakes. This study uses sediment cores to assess the history of mercury (Hg) deposition and to assess changes occurring in autochthonous productivity in these lakes. Sediments deposited after the onset of the industrial revolution contained significantly higher concentrations of Hg, with the highest concentrations found in the most recently deposited sediments. Hg concentrations in these pristine lakes rival those of lakes in heavily urbanized areas, indicating that they are in fact subjected to atmospheric deposition of Hg. There was a large variation in [Hg] of the surface sediments of 13 lakes; underscoring the importance of in situ processes in the fate of atmospherically deposited Hg. Methylmercury (MeHg) concentrations were not correlated with total mercury concentrations (THg), demonstrating how THg is a poor predictor of MeHg; the bioaccumulative neurotoxic form of mercury. The S2 fraction of Rock-Eval® Pyrolysis, C:N ratios and ∂13C signatures were used as proxies of autochthonous carbon and all indicated that the lakes have become increasingly productive, presumably due to warmer water temperatures and longer ice-free seasons. Additionally, I use molecular techniques to detect and quantify the merA gene in the sediment; a proxy of bacterial mercury resistance involved in redox transformations. In Aquatuk, Hawley and North Raft Lakes, I observed a subsurface increase in merA genes in the sediment core, independently of a control gene and the [THg]. While I have not been able to explain the driving variables of this subsurface increase, I believe that the role of merA within remote lake sediments deserves further work. Lastly, microcosms were used to measure the production of volatile elemental mercury (Hg(0)) from surface sediments of Aquatuk Lake. I used a combination of analytical and molecular techniques to show that the production of Hg(0) is biogenic and tested the effect of nutrients, pH and ionic strength on the Hg(0) production rates. Ionic strength alone had the greatest impact on Hg(0) production rates, with increased Hg(0) production as ionic strength increases.
dc.language.isoen
dc.publisherUniversité d'Ottawa / University of Ottawa
dc.subjectmercury
dc.subjectorganic matter
dc.subjectbacterial mercury resistance
dc.subjectmer operon
dc.subjectlake sediment
dc.subjectHudson Bay Lowlands
dc.titleHistorical Deposition and Microbial Redox Cycling of Mercury in Lake Sediments from the Hudson Bay Lowlands, Ontario, Canada
dc.typeThesis
dc.faculty.departmentBiologie / Biology
dc.contributor.supervisorBlais, Jules M.
dc.contributor.supervisorPoulain, Alexandre J.
dc.embargo.termsimmediate
dc.degree.nameMSc
dc.degree.levelmasters
dc.degree.disciplineSciences / Science
thesis.degree.nameMSc
thesis.degree.levelMasters
thesis.degree.disciplineSciences / Science
uottawa.departmentBiologie / Biology
CollectionThèses, 2011 - // Theses, 2011 -

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