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Nitrate as an Electron Acceptor in M...

Bulseco-McKim, Ashley.

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Nitrate as an Electron Acceptor in Microbial Decomposition of Salt Marsh Sediment Organic Matter and Implications for Carbon Storage.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Nitrate as an Electron Acceptor in Microbial Decomposition of Salt Marsh Sediment Organic Matter and Implications for Carbon Storage./
作者:	Bulseco-McKim, Ashley.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
面頁冊數:	244 p.
附註:	Source: Dissertation Abstracts International, Volume: 80-01(E), Section: B.
Contained By:	Dissertation Abstracts International80-01B(E).
標題:	Biogeochemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10931316
ISBN:	9780438309111

Nitrate as an Electron Acceptor in Microbial Decomposition of Salt Marsh Sediment Organic Matter and Implications for Carbon Storage.
Bulseco-McKim, Ashley.

Nitrate as an Electron Acceptor in Microbial Decomposition of Salt Marsh Sediment Organic Matter and Implications for Carbon Storage. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 244 p.

Source: Dissertation Abstracts International, Volume: 80-01(E), Section: B.

Thesis (Ph.D.)--Northeastern University, 2018.

Atmospheric carbon dioxide (CO2) concentrations continue to rise as a result of fossil fuel burning and land-use changes, thereby contributing to increases in global temperature, ocean acidification, and sea level rise. Sequestering some of this excess CO2 in blue carbon habitats, such as salt marshes, mangroves, and seagrasses, has been proposed as a mitigation strategy due to their ability to efficiently store carbon. Salt marshes, in particular, store carbon at rates that are orders of magnitude greater than terrestrial forests due to large inputs of organic matter (OM) from primary production concurrent with slow decomposition rates; the balance between the two ultimately determines the burial of OM and carbon storage over time. As nitrogen loading to coastal waters continues to rise, primarily in the form of nitrate (NO 3-), it is unclear what effect it will have on carbon storage capacity of these systems. This uncertainty is largely driven by the dual role NO 3- can play in biological processes, where it can either serve as a nutrient for primary production or a powerful electron acceptor fueling heterotrophic microbial metabolism. Distinguishing between the two is critical, since the former could promote carbon storage by enhancing fixation, while the latter could potentially deplete this service by stimulating microbial decomposition.

ISBN: 9780438309111Subjects--Topical Terms:

545717
Biogeochemistry.

Nitrate as an Electron Acceptor in Microbial Decomposition of Salt Marsh Sediment Organic Matter and Implications for Carbon Storage.
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245 1 0 $a Nitrate as an Electron Acceptor in Microbial Decomposition of Salt Marsh Sediment Organic Matter and Implications for Carbon Storage.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2018
300 $a 244 p.
500 $a Source: Dissertation Abstracts International, Volume: 80-01(E), Section: B.
500 $a Adviser: Jennifer L. Bowen.
502 $a Thesis (Ph.D.)--Northeastern University, 2018.
520 $a Atmospheric carbon dioxide (CO2) concentrations continue to rise as a result of fossil fuel burning and land-use changes, thereby contributing to increases in global temperature, ocean acidification, and sea level rise. Sequestering some of this excess CO2 in blue carbon habitats, such as salt marshes, mangroves, and seagrasses, has been proposed as a mitigation strategy due to their ability to efficiently store carbon. Salt marshes, in particular, store carbon at rates that are orders of magnitude greater than terrestrial forests due to large inputs of organic matter (OM) from primary production concurrent with slow decomposition rates; the balance between the two ultimately determines the burial of OM and carbon storage over time. As nitrogen loading to coastal waters continues to rise, primarily in the form of nitrate (NO 3-), it is unclear what effect it will have on carbon storage capacity of these systems. This uncertainty is largely driven by the dual role NO 3- can play in biological processes, where it can either serve as a nutrient for primary production or a powerful electron acceptor fueling heterotrophic microbial metabolism. Distinguishing between the two is critical, since the former could promote carbon storage by enhancing fixation, while the latter could potentially deplete this service by stimulating microbial decomposition.
520 $a Using a combination of controlled flow through experiments and field surveys, my dissertation sought to: 1) determine the importance of NO 3- as an electron acceptor in OM decomposition across different sediment depths, 2) assess whether chronic NO3- enrichment affected OM burial, and, since microbes are largely responsible for controlling long term carbon storage, 3) examine microbial community diversity, structure, activity, and assembly of deep salt marsh sediments spanning over 3000 years of accretion between two sites: an experimentally enriched marsh and its paired reference marsh. To carry out these objectives, I applied a comprehensive set of tools, including 1) biogeochemical measurements of dissolved inorganic carbon and nutrient concentrations, 2) OM quality measurements, such as % carbon, % nitrogen, lipid biomarkers concentration, and Fourier Transform-Infrared Spectroscopy, as well as 3) sequencing of the 16S rRNA gene, its product 16S rRNA, and shotgun metagenomics.
520 $a In controlled flow through experiments where I exposed sediment of varying depths and OM lability to 500 microM NO3-, I observed a 40-45% increase in OM decomposition in response to NO3- when compared to a seawater control. This pattern persisted at sediment depths typically considered to be less labile. NO3- altered both the microbial community and its associated functional potential, selecting for taxa belonging to groups known to reduce NO3- and oxidize more complex forms of OM, and increasing the abundance of nitrogen cycling genes. Stimulation in OM decomposition in response to NO3- was not as pronounced in sediments from sites that had been chronically exposed to NO3-, with the lowest effect size occurring at a site exposed to sewage effluent for 40 years, suggesting the effect of NO3- on OM decomposition is limited. These results demonstrate that NO3- can serve as an electron acceptor in microbial metabolism and may expand the OM pool available to microbial oxidation, effectively reducing overall carbon storage potential in salt marsh systems, however, OM that is buried under high NO3- conditions may be more stable over time.
520 $a In a field survey examining microbial community diversity, structure, activity, and assembly of deep salt marsh sediments spanning over 3000 years of accretion between an experimentally enriched marsh and its paired reference marsh, I found that both microbial diversity and gene abundance decreased with depth, potentially due to resource limitation, and observed high rates of inactivity in deeper sediments. Depth and associated changes in OM explained changes in microbial community structure in shallow (0-50 cm) sediments, but this pattern became much less apparent in deeper sediments beyond the rooting zone (60+ cm), likely due to more stochastic assembly at depth. The only difference between the reference and enriched marshes occurred in deeper sediments, suggesting that the effect of nutrient enrichment is not detectable over longer time scales of carbon storage; instead, these differences may be attributed to stochastic processes resulting from energy limitation in deep subsurface marsh sediments. Overall, my dissertation highlights the role of NO3- as an electron acceptor in OM decomposition, and underscores the need to better understand the microbes mediating carbon storage and how they will respond to nutrient enrichment.
590 $a School code: 0160.
650 4 $a Biogeochemistry. $3 545717
650 4 $a Microbiology. $3 536250
650 4 $a Soil sciences. $3 2122699
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710 2 $a Northeastern University. $b Marine and Environmental Sciences. $3 3282673
773 0 $t Dissertation Abstracts International $g 80-01B(E).
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