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Week 4 Lectures November 2001

Week 4 Lectures November 2001. Microbial Ecology and Geochemical Cycles. This Week’s Lecture. Microbial Ecology Importance of Oxic/Anoxic Environment Geochemical Cycles Applications. Microbial Ecology.

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Week 4 Lectures November 2001

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  1. Week 4 LecturesNovember 2001 Microbial Ecology and Geochemical Cycles

  2. This Week’s Lecture • Microbial Ecology • Importance of Oxic/Anoxic Environment • Geochemical Cycles • Applications

  3. Microbial Ecology • Understand the biodiversity of microorganisms and how different metabolically diverse organisms interact • Monitor the activities of microorganisms and their impact on ecosystems

  4. Important Terms • Environment: everything surrounding microorganism including the physical, biological, and chemical factors that act on the organism • Populations of individual microbial species • Guilds are metabolically related populations • The microbial community is made up of guilds

  5. Oxic Anoxic Sediments Guilds and Communities • Community 2: Oxic Zone • Chemoorganoheterotrophs • Chemolithoautotrophs • Guild 1: nitrifiers • Guild 2: sulfur oxidizing bacteria Community 1 • Photic zone • algae • cyanobacter • Community 3: Anoxic Zone • Chemoorganoheterotrophs • Guild 3: denitrifiers • Guild 4: sulfate reducers • Guild 5: fermenters • Chemolithoautotrophs • Guild 6: methanogens • Guild 7: sulfate reducers

  6. Microbial Habitats and the Oxic/Anoxic Interface • Oxygen clearly plays an important role in determining the range of microbial mediated reactions that occur in any environment • It is important to understand the relationships between these two environments and the factors that lead to the formation of both

  7. Oxygen Relationships in Lake Ecosystems { Epilimnion: oxygen concentration relatively uniform and may be as higher as near saturation Oxic { Thermocline: zone of sharp temperature gradient that separates the epilimnion and hypolimnion { Hypolimnion: zone of unmixed water having low oxygen content Anoxic Sediments

  8. Wastewater Discharge Dissolved Oxygen mg/L Low Dissolved Oxygen Distance Downstream Oxygen Relationships in Surface Waters (Streams and Rivers)

  9. Oxygen Relationships in Groundwater • Groundwater constituents that consume oxygen include: • dissolved organic carbon (plant exudates, etc. • methane • inorganics • reduced nitrogen • reduced iron • Typically oxygen concentrations decrease with travel distance

  10. Terrestrial Ecosystems O horizon: layer of undecomposed plant material A horizon: surface soil high in organic matter and high microbial activity B horizon: subsoil; minerals and humus leached from A horizon accumulate, little organic matter C horizon: soil base with low microbial activity

  11. Interrelationship Between Moisture Content and Oxygenation in Soils • Soils that retain water tend to be more susceptible to anaerobic conditions • Clays and silts

  12. Microenvironments Using Soil as an Example Distance, mm Distance, mm

  13. Geochemical Cycles • oxidation/reduction reactions that describe the changes in an element as it passes through an ecosystem • geochemical cycles then are of interest for elements that undergo oxidation/reduction reactions (C, S, N, Fe, and others) • as shown before, oxygen plays a key role in metabolic reactions and is a major consideration in the description of geochemical cycles

  14. Carbon Geochemical Cycle

  15. Nitrogen Geochemical Cycle

  16. Sulfur Geochemical Cycle

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