Thesis
Thermal stratification impacts microbial nitrogen removal and nitrous oxide production in a small eutrophic reservoir: An in-situ approach to quantifying hypolimnetic process rates
Washington State University
Master of Science (MS), Washington State University
2010
Handle:
https://hdl.handle.net/2376/102154
Abstract
Identifying patterns and controls on microbial N removal and N2O production is a critical step in understanding the role that freshwater systems play as both N filters and greenhouse gas sources. Efforts to discern these relationships have been limited by methodological difficulties associated with the measurement of these processes. In this study, N dynamics within the hypolimnion of a thermally stratified reservoir were examined in order to test a novel approach to measuring in situ N2 and N2O production rates wherein sub-thermocline gas accumulation rates serve as a proxy for sediment production rates. Water column stratification can significantly change bottom water chemistry and was thus expected to impact system N2 and N2O production rates. Potential denitrification rates determined by acetylene block were three orders of magnitude greater in the sediment than in the overlying water column. These assays, sediment incubation experiments, and hypolimnion NO− 3 data show that, over the course of the summer, progressive nitrate depletion at the sediment-water interface limited N2 production and associated N removal. As rates of N2 production dropped off, rates of N2O production increased, resulting in significant increases in N2O:N2 ratios as the summer progressed (p <0.05). These findings have important implications for the incorporation of seasonal patterns of aquatic N removal in N transport models. Our findings also suggest that physical disturbances, such as dam spills, may sufficiently destabilize the water column to alleviate sediment NO− 3 limitation
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Details
- Title
- Thermal stratification impacts microbial nitrogen removal and nitrous oxide production in a small eutrophic reservoir
- Creators
- Bridget Read Deemer
- Contributors
- John A. Harrison (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525053701842
- Language
- English
- Resource Type
- Thesis