A Combined Molecular and Isotopic Study of Sulfur Bacteria in Meromictic Lakes of the Pacific Northwest

dc.contributor.advisorGilhooly, William P., III
dc.contributor.authorHarris, James H., IV
dc.contributor.otherDruschel, Gregory K.
dc.contributor.otherBird, Broxton W.
dc.date.accessioned2024-01-04T09:04:53Z
dc.date.available2024-01-04T09:04:53Z
dc.date.issued2023-12
dc.degree.date2023
dc.degree.disciplineDepartment of Earth Scienceen
dc.degree.grantorIndiana University
dc.degree.levelM.S.
dc.descriptionIndiana University-Purdue University Indianapolis (IUPUI)en
dc.description.abstractThe isotope effects that result from the activity of modern sulfur metabolizing bacteria serve as analogs to interpreting the sulfur isotope values preserved in the geologic record. This biogenic signal is vital to reconstructing the history of Earth’s ancient oceans and atmosphere. However, the isotope compositions imprinted by these bacteria were influenced by multiple factors that must be considered when using these values to make interpretations about environmental change. These factors include: (1) sulfate availability, (2) the rapid and quantitative reoxidation of sulfide (i.e., cryptic sulfur cycling), (3) the initial oxygen isotope compositions of sulfate and water, and (4) the taxonomic structure of sulfur-metabolizing bacterial communities. To address these questions, this project studied four permanently stratified, anoxic and sulfidic (euxinic), lakes in southern British Columbia, Canada, and northern Washington, USA, that have a wide range of sulfate concentrations, from 0.15 – 120 mM. This project resulted in six key findings – (1) the measurement of large Δ34SSO4-H2S values at micromolar sulfate concentrations, (2) the consistent occurrence of δ18OSO4 minima at the chemocline that may be imparted during cryptic sulfur cycling, (3) that subsequent δ18OSO4 enrichments consistently preceded sulfide accumulation and δ34SSO4 enrichment in the suboxic zone of the water column, (4) that initial epilimnion Δ18OSO4-H2O values placed constraints on the maximum extent of δ18OSO4 evolution that occurred beneath the chemocline, (5) that observable changes in the metabolic composition of sulfur bacterial communities accompanied key inflections in the sulfur and oxygen isotope profiles of sulfate and sulfide within the water column, and (6) that, despite large overall differences in community structure, Δ34SSO4-H2S and Δ18OSO4-H2O values ultimately reached similar magnitudes in each lake.
dc.identifier.urihttps://hdl.handle.net/1805/37590
dc.language.isoen_US
dc.subjectstable isotopes
dc.subjectsulfur bacteria
dc.subjectcryptic sulfur cycle
dc.subject34S
dc.subject18O
dc.subjectbiogeochemistry
dc.subjectgeobiology
dc.subjectfunctional analysis
dc.subjectcommunity structure
dc.subjecteuxinic
dc.subjectisotope fractionation
dc.subjectdissimilatory sulfate reduction
dc.subjectSox
dc.subjectsulfur disproportionation
dc.subject34SSO4
dc.subject34SH2S
dc.subject18OSO4
dc.subjectsulfur cycle
dc.subjectgreen sulfur bacteria
dc.subjectpurple sulfur bacteria
dc.subjectsulfate reducing bacteria
dc.subjectLakewater
dc.subjectStratified
dc.subjecthypolimnion
dc.subjectchemocline
dc.subjectsulfate concentration
dc.subjectcryptic sulfur cycling
dc.subjectillumina
dc.subjectmetagenomics
dc.subject16s gene
dc.subjectmicrobial ecology
dc.subjectenvironmental gene sequencing
dc.subject16s rRNA
dc.titleA Combined Molecular and Isotopic Study of Sulfur Bacteria in Meromictic Lakes of the Pacific Northwest
dc.typeThesisen
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