Biology Theses and Dissertations

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Browsing Biology Theses and Dissertations by Subject "Anaerobic"

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    Examining Anaerobic Oxidation of Methane in a Northern Peat Bog
    (University of Oregon, 2020-02-27) McCullough, Laura; Bridgham, Scott
    Globally, about one-third of annual methane (CH4) emissions from natural sources come from freshwater wetlands. Scientists need a strong understanding of CH4 cycling to predict how climatic shifts will affect future CH4 emissions. Anaerobic oxidation of CH4 (AOM) is an important factor in CH4 cycle models in marine systems, but it has so far been excluded from freshwater CH4 cycle models which balance production and aerobic consumption. However, evidence for AOM as an influential part of CH4 cycling in freshwater ecosystems is mounting, revealing that traditional methods for measuring CH4 production and modeling CH4 cycling may need updating. Here, we present a new method for measuring AOM and gross CH4 production simultaneously during incubation using a 13CH4 tracer. This study supports existing evidence that AOM is an influential part of CH4 cycling in peatlands and presents evidence that the process can occur to a depth of at least 2 meters.
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    ItemOpen Access
    Seasonal Dynamics of Methane Pathways Along a Hydrogeomorphic Peatland Gradient
    (University of Oregon, 2016-10-27) McAllister, Steven; Bridgham, Scott
    Northern peatlands occupy a very small proportion of the Earth’s surface but contain nearly a third of the world’s soil organic carbon. These wetland systems produce substantial fluxes of CH4, a potent greenhouse gas, and are expected to experience particularly high annual mean temperature increases as global climate change proceeds, which could result in a significant positive feedback. Using radioisotope labeling, we quantified the rates of two pathways of CH4 production in six sites in northern Michigan along a physiochemical and ecological gradient that characterizes northern peatlands. We found that the rates of these two pathways displayed markedly different dynamics in space and time and that the hydrogenotrophic pathway, previously presumed to be less significant in these systems, can increase substantially and become dominant across the landscape when water tables are high. Quantifying these two pathways provides critical insight into understanding dynamics of CH4 production in northern peatlands.