Browsing by Subject "sulfur"

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    Biogeochemical Interactions And Ecological Consequences Of Sulfur In Stands Of Wild Rice
    (2020-05) LaFond-Hudson, Sophia
    Wild rice is an ecologically and culturally important plant that typically grows in lakes and rivers in Minnesota that have low sulfate concentrations. Previous work demonstrated that elevated sulfate concentrations contribute to the decline in wild rice populations when conditions allow for the reaction of sulfate to sulfide. This dissertation investigates the fate of sulfate in the rooting zone of wild rice, mechanisms and consequences of sulfide exposure to plants, and the long-term effects of sulfide exposure on population dynamics. Key findings include 1) iron plaques on root surfaces transition from iron oxide to iron sulfide during reproduction if sulfate is elevated; 2) in elevated sulfate, seed production is delayed and shortened and plants produce fewer, smaller seeds with less nitrogen; and 3) populations of wild rice grown in low sulfate have stable biomass oscillations with a period of approximately 4 years, but elevated sulfate destabilizes these cycles and drives the population toward extinction.
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    Iron Sulfide Formation on the Root Surfaces of Wild Rice
    (2017-08-16) LaFond-Hudson, Sophia; Johnson, Nathan; Pastor, John; Dewey, Brad; lafo0062@d.umn.edu; LaFond-Hudson, Sophia
    The data are from an experiment showing life-cycle induced iron sulfide formation on root surfaces of wild rice. Plants with and without added sulfate were harvested during the reproductive stage of the life cycle to quantify concentrations of iron and sulfide on root surfaces. Seed and plant N was measured to examine the effect of iron sulfide root plaques on seed production. On amended roots, iron transitioned from mostly Fe(III) to mostly Fe(II) as sulfide concentrations increased rapidly. Amended plants produced fewer, lighter seeds with less nitrogen.
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    Sulfur bacteria promote dissolution of authigenic carbonates at marine methane seeps
    (2021-01-27) Leprich, Dalton J.; Flood, Beverly E.; Schroedl, Peter R.; Ricci, Elizabeth; Marlow, Jeffery J.; Girguis, Peter R.; Bailey, Jake V.; beflood@umn.edu; Flood, Beverly E.; University of Minnesota Bailey Geobiology Lab
    Carbonate rocks at marine methane seeps are commonly colonized by sulfur-oxidizing bacteria that co-occur with etch pits that suggest active dissolution. We show that sulfur-oxidizing bacteria are abundant on the surface of an exemplar seep carbonate collected from Del Mar East Methane Seep Field, USA. We then used bioreactors containing aragonite mineral coupons that simulate certain seep conditions to investigate plausible in situ rates of carbonate dissolution associated with sulfur-oxidizing bacteria. Bioreactors inoculated with a sulfur-oxidizing bacterial strain, Celeribacter baekdonensis LH4, growing on aragonite coupons induced dissolution rates in sulfidic, heterotrophic, and abiotic conditions of 1773.97 (±324.35), 152.81 (±123.27), and 272.99 (±249.96) Mol CaCO3  cm-2  yr-1, respectively. Steep gradients in pH were also measured within carbonate-attached biofilms using pH-sensitive fluorophores. Together, these results show that the production of acidic microenvironments in biofilms of sulfur-oxidizing bacteria are capable of dissolving carbonate rocks, even under well-buffered marine conditions. Our results support the hypothesis that authigenic carbonate rock dissolution driven by lithotrophic sulfur-oxidation constitutes a previously unknown carbon flux from the rock reservoir to the ocean and atmosphere.