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Exploring Microbial Phosphorus Accessibility in Response to Changing Iron Mineralogy and Redox Conditions

Smith, Chelsea Elizabeth
http://orcid.org/0000-0003-1728-2609
http://rave.ohiolink.edu/etdc/view?acc_num=kent1700321631798529

Abstract Details

2023, PHD, Kent State University, College of Arts and Sciences / Department of Biological Sciences.
Climate change is exerting profound and far-reaching impacts on ecosystems worldwide, encompassing both aquatic and terrestrial environments. The evolving precipitation patterns and shifting temperature regimes impact fluctuations in hydrology, resulting in shifts in redox conditions which can impact the availability of nutrients like phosphorus (P). Phosphate, the bioavailable form of P, is only present in small amounts within soils, making the biological demand greater than soil phosphate availability. The majority of soil P is present in non-labile forms including organic P and phosphate sorbed to metal oxides like iron (Fe). Microorganisms must content with geochemical and other abiotic factors to access phosphate from these non-labile sources through the use of various strategies including the secretion of enzymes, the production of phosphate solubilizing acids, as well as indirect mechanisms associated with the reduction of Fe oxides. The primary goal of this dissertation was to advance our understanding of how microorganisms access both labile and non-labile forms of P in the presence of changing hydrologic and redox conditions which impact the speciation of Fe that is present, altering phosphate availability. Specifically, I investigated 1) how phosphate availability changes across a permafrost thaw gradient (palsa, bog, and fen) in the presence of iron oxides, 2) how microorganisms access and mobilize chemically diverse phosphorus sources under contrasting redox conditions, and 3) how changes in hydrology, redox, iron mineralogy, and phosphate availability drive shifts in microbial community composition, specifically iron oxidizers, reducers, and phosphate solubilizers. In our first study assessing microbial phosphate accessibility across a permafrost thaw gradient, we found that near surface redox conditions changed as a function of permafrost thaw which impacted phosphate availability. Reducing conditions in the bog promoted the dissolution of Fe oxides, releasing phosphate from Fe mineral surfaces, resulting in greater microbial biomass P concentrations. In our P source microcosm experiment, we found that generally, microbes can access and transform both labile and non-labile sources of P under both oxidizing and reducing conditions. We additionally found that even under reducing conditions, Fe oxides can persist and continue to trap phosphate over time in treatments that contained an iron-phosphate source as well as treatments containing an organic P source. Lastly, we also found that like Fe oxides, aluminum oxides, and likely clays, trap large amounts of phosphate, irrespective of redox conditions. In our final study which examined how changes in hydrology, redox, iron mineralogy, and phosphate availability cause shifts in microbial community composition, we found that Fe oxidizing genera were mainly found in dry to semi-wet, oxidizing environments while Fe reducing genera were mainly found in inundated to semi-wet, reducing conditions. The presence of phosphate solubilizing genera were only found in dry, oxidizing environments which suggests phosphate limited conditions under these circumstances. Additionally, we did not find inherent changes in microbial community composition in response to different Fe crystallinities. Lastly, the final chapter of this dissertation provides future directions which include recommendations on how to better assess specific microbial phosphate acquisition strategies to better identify which mechanisms are at play in response to P limitation.
Lauren Kinsman-Costello (Advisor)
Christie Bahlai (Committee Member)
David Costello (Committee Member)
Christopher Blackwood (Committee Member)
Elizabeth Herndon (Committee Member)
Timothy Gallagher (Committee Member)
183 p.
Biogeochemistry; Climate Change; Ecology; Geobiology; Geochemistry; Microbiology; Mineralogy; Soil Sciences
Phosphorus; Iron; Iron Oxides; Soil Ecology; Microbial Ecology; Biogeochemistry; Redox; Mineralogy; Soil; Sediment; Arctic; Permafrost Thaw; Vernal Pond

Recommended Citations

Citations

  • Smith, C. E. (2023). Exploring Microbial Phosphorus Accessibility in Response to Changing Iron Mineralogy and Redox Conditions [Doctoral dissertation, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent1700321631798529

    APA Style (7th edition)

  • Smith, Chelsea. Exploring Microbial Phosphorus Accessibility in Response to Changing Iron Mineralogy and Redox Conditions. 2023. Kent State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent1700321631798529.

    MLA Style (8th edition)

  • Smith, Chelsea. "Exploring Microbial Phosphorus Accessibility in Response to Changing Iron Mineralogy and Redox Conditions." Doctoral dissertation, Kent State University, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=kent1700321631798529

    Chicago Manual of Style (17th edition)

kent1700321631798529
123
© 2023, all rights reserved.
This open access ETD is published by Kent State University and OhioLINK.