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Geomicrobiology at the Sevilleta

Geomicrobiology at the Sevilleta. By Samantha Adelberg Mentors: Laura Crossey and Amy Williams. Predicting the metabolic energy available to aqueous microorganisms. Water. Sources of Water at the Sevilleta Rio Grande Precipitation Groundwater Wells and Springs. Groundwater.

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Geomicrobiology at the Sevilleta

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  1. Geomicrobiology at the Sevilleta By Samantha Adelberg Mentors: Laura Crossey and Amy Williams Predicting the metabolic energy available to aqueous microorganisms

  2. Water • Sources of Water at the Sevilleta • Rio Grande • Precipitation • Groundwater Wells and Springs

  3. Groundwater • 25 wells and springs • Minimal Knowledge • Some Previous Research

  4. Research Question • Water chemistries varying dramatically within the Sevilleta due to local geology • But how much does the varying water chemistry affect the thermodynamics of the different springs and wells?

  5. Thermodynamics • All reactions want to move towards an equilibrium state • Natural waters such as the ones at the Sevilleta are not in equilibrium • Energetically favorable for these reactions to move from one state to another • Spontaneous reactions, - delta G • But there is no set time limit Affinity = RT ln(K/Q) Gas constant Equilibrium constant Temperature

  6. Role of Microorganisms • Act as catalysts in these reactions • Speed up the electron transfers • Must spend energy making enzymes that can perform these reactions • Facilitate these reactions because they gain a determined amount of energy through each transaction • Amount of energy gained changes

  7. Chemo-litho-auto-troph “Eater of” Energy Source: Chemical reactions Carbon source: Inorganic Electron Donor: Inorganic Chemolithoautotroph Photoautotroph Heterotroph

  8. Gibbs Free Energy

  9. Study Area: Sevilleta Springs and Wells

  10. Methods • In the Field • pH, conductivity , TDS, temp • Bottles for cations, anions, stable isotopes, nutrients, delta 13C • In the Lab • Alkalinity (endpoint titrations) • ICP: cations and trace elements • IC: anions • Nutrients • Analysis • Geochemical modeling software Phreeqc • Thermodynamics code to determine electron affinity

  11. PICTURE of LOCAL GEOLOGY

  12. Rio Salado Box Springs West Mesa Tomasino Silver Creek San Acacia Cibola

  13. Deeply Derived Waters Rio Salado Box Springs San Acacia Spring CoCorp Siesmic Line, Lewis and Baldridge 1994

  14. Results

  15. Top 5 Reactions for all Springs/Wells

  16. What does this show? • What reactions can occur • The potential energy yield of the different reactions • What niche spaces are available for use • Trends between the geology, water chemistry, and affinity coefficients

  17. Affinity Trends • Chloride Dominated Waters (San A-C, RSB12) have nearly identical affinity coefficients • P value = .94

  18. The Chloride Dominated Waters San Acacia Spring Rio Salado Box Spring

  19. Affinity Trends • Geographically similar location (SdC1, TW) • Distinct water types • Sulfate Dominated (Cibola Spring) • Mixed Ion Water (Tomasino Well) • P value = .925

  20. PICTURE of LOCAL GEOLOGY Tomasino Cibola

  21. Affinity Trends • Bicarbonate Dominated Waters (WMW, SC2) • P value = .665

  22. Nutrient Readings C:N ratios limiting nutrients whose presence greatly affects the health of a water system > 14.6 severe N deficiency 8.3 –14.6 moderate deficiency <8.3 no deficiency Only Tomasino Well does not have a severe N deficiency All Springs/Wells have high TOC readings which predict the presence of chemolithoheterotrophs

  23. Gibbs Free Energy Discussion • Nitrate is the dominant electron acceptor • Nutrient reading show that all but one spring/well is deficient in N • This is probably because NO3 is being used nearly entirely in these metabolic reactions • Surprisingly, in the springs/wells with O2, Nitrate continues to have a higher energy yield • Perhaps because O2 is so limited that it isn’t optimal for microorganisms to use this pathway • Feedback effect between microbs and water

  24. Lower than atmos. pCO2 yet saturated with respect to calcite Higher than atmos. pCO2 and saturated with calcite Higher than atmos. pCO2 yet under saturated with respect to calcite

  25. Crossey, unpublished

  26. Why use thermodynamic modeling? • Future geomicrobiology research and sampling • Provides explanations • Similarities to Mid Ocean Ridge thermal vents Marine vent systems Continental spring systems Rio Grande Rift; Crossey et al., in prep. Lost City Hydrothermal area, Kelley et al., 2005

  27. Acknowledgements - Laura Crossey - Amy Williams - Frankie Reyes - All the REU’s! - Jennifer Johnson - Scott Collins • Fish and Wildlife Services • NSF • Sevilleta LTER • Ara Kooser • Brandi Cron • Amanda Martinez • Cathy! • Mehdi and Kim in the analytical chemistry lab • Amanda Schaupp, my statistician!

  28. QUESTIONS?

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