Trophic Ecology

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Trophic Ecology

• What are the trophic interactions in streams
• Microbial Loop
• Invertebrate consumers
• Consumers of CPOM
• Consumers of FPOM
• Herbivores consumers of autotrophs
• Predators consumers of other animals
• Fish consumers
• Herbivores
• Predators

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Trophic Ecology
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Trophic Ecology
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Microbial Loop

• Composition of stream microorganisms
• Autotrophs (blue-green and eukaryotic algae)
• Heterotrophs (bacteria, fungi, protozoans)

Figure 6.1
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Microbial Loop

• Heterotrophic microorganisms
• Quantification of bacterial biomass
• Culturing in media
• Microscopic enumeration (e.g. epifluorescence)
• Metabolic processes (e.g. respiration, nutrient
  uptake/transformation, tritiated thymidine
  uptake)
• Chemical constituents (e.g. ATP)
• Distribution of stream heterotrophs
• Microorganisms are concentrated in the sediments
  and decline with depth into the sediments,
  especially into anaerobic zones
• Areas of organic deposition (e.g., backwaters,
  wetted floodplains) are important areas of
  microbial activity

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Microbial Loop

• Aerobic decomposition
• Detritus decomposition
• Detritus - dead organic matter, both dissolved
  and particulate, that makes up the majority of
  organic carbon in streams
• Bacterial uptake of dissolved organic carbon
  (DOC)
• Proteins and amino acids - rapid uptake
• Carbohydrates - rapid uptake
• Fatty acids lipids) - decomposed readily
• Organic acids (e.g. humic acids) - slow uptake
• Biotic release of DOC
• Autolysis - release of DOC as organisms senesce
  and die, brought on by deterioration of cell
  membranes
• Secretion - extra cellular release of DOC from
  actively growing bacteria and aquatic plants

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Microbial Loop

• Anaerobic decomposition
• Hydrolysis - breakdown of complex carbohydrates,
  proteins, and lipids to smaller "building-block"
  compounds such as amino acids, simple sugars, and
  fatty acids
• Ammonification (organic N to ammonium) is one
  product of hydrolysis which may regenerate
  nutrients to overlying waters
• Fermentation - anaerobic decomposition of simple
  sugars, fatty acids, and amino acids to smaller
  fatty acids, alcohols, H2, and C02
• Terminal electron accepting stage - nutrient
  transformations as end product of anaerobic
  metabolism
• Denitrification (N03- to N2)
• Sulfate reduction (S04-2 to H2S)
• Methanogenesis (C02 to CH4)

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Microbial Loop

• Stream microorganisms

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Microbial Loop

• Stream microorganisms

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Microbial Loop

• Stream microorganisms

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Microbial Loop FPOM Collector Diagram
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Microbial Loop FPOM Collector Diagram
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Trophic Ecology
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Trophic Ecology
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