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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. - PowerPoint PPT Presentation
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Week 4 LecturesNovember 2001
Microbial Ecology and Geochemical Cycles
This Week’s Lecture
Microbial Ecology
Importance of Oxic/Anoxic Environment
Geochemical Cycles
Applications
Microbial Ecology
Understand the biodiversity of microorganisms and how different metabolically diverse organisms interact
Monitor the activities of microorganisms and their impact on ecosystems
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
Guilds and Communities
Sediments
Anoxic
Oxic
Community 1 Photic zone
algae cyanobacter
Community 2: Oxic Zone Chemoorganoheterotrophs Chemolithoautotrophs
Guild 1: nitrifiers Guild 2: sulfur oxidizing
bacteria
Community 3: Anoxic Zone Chemoorganoheterotrophs
Guild 3: denitrifiers Guild 4: sulfate reducers Guild 5: fermenters
Chemolithoautotrophs Guild 6: methanogens Guild 7: sulfate reducers
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
Oxygen Relationships in Lake Ecosystems
Sediments
Anoxic
OxicEpilimnion: oxygen concentration relatively uniform and may be as higher as near saturation
Hypolimnion: zone of unmixed water having low oxygen content
Thermocline: zone of sharp temperature gradient that separates the epilimnion and hypolimnion
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Oxygen Relationships in Surface Waters (Streams and Rivers)
Wastewater Discharge
Distance DownstreamDis
solv
ed O
xyge
n m
g/L
Low Dissolved Oxygen
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
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
Interrelationship Between Moisture Content and Oxygenation in Soils
Soils that retain water tend to be more susceptible to anaerobic conditions
Clays and silts
Microenvironments Using Soil as an Example
Distance, mm
Dis
tanc
e, m
m
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
Carbon Geochemical
Cycle
Nitrogen Geochemical Cycle
Sulfur Geochemical Cycle
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