Heterotrophy

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Heterotrophy
Input of CPOM (gt1mm) occurs throughout the year
Fall Winter
Spring Summer

• Leaves
• Needles
• 54 of total litter input to Bear Brook, NH

• Flowers
• Seeds

• Flowers
• Fruit
• Seeds
• Frass

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Litterfall composition, Glenwild Lake, NJ
Sebetich Horner-Newfeld (2000)
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Fate of allochthonous material once it enters a
stream

• Breakdown - Function of
• Physical
• Chemical
• Biological actions
• Transport Function of
• Discharge
• Streambed composition

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From Webster et al. (1999)
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Effect of discharge on organic matter
concentration in streams
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• CPOM trapped more efficiently by
• Channel roughness
• Backwaters
• Debris dams

• Trapping efficiency can be determined
  experimentally
• Leaves small wood may travel lt10 meters
  downstream
• (about 100m during spate)
• FPOM travels about 200m downstream

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• Fate of CPOM
• Leaching
• Microbe colonization
• Fragmentation

(Allan 1995)
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Microbes

• Decompose leaves and other o.m.
• Make leaves more palatable nutritious to
  shredders
• e.g., Cummins cracker peanut butter example

Fragmentation

• By invertebrates
• About 25 of leaf degradation is due to
• invertebrate animals

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FPOM (0.45-1000 µm)

• examples fragments, fine terrestrial particles,
  algae, feces of invertebrates
• More easily transported due to the small size
• Availability to consumers influenced by discharge
  and instream obstructions
• FPOM travel in stream 200m
• FPOM feeders ingest gt4x their weight/day
• Total standing crop of FPOM in Sycamore Creek, AR
  injested and egested every 2-3 days

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DOM

• Sources
• Soil o.m. shallow groundwater (2-30 mg/L)
• Precipitation (1 mg/L)
• Below canopy (2-3 mg/L)
• Canopy drip (25 mg/L)
• Extracellular releases from algae
• Leaf leachate of DOC
• Fate
• Taken up rapidly (within 48-72 hrs)
• Adsorption onto clays
• Complexation reactions w/Al Fe
• Flocculation
• Photochemical destruction

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Annual Energy Budget for Bear Brook, NH
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Food (energy) Processing

• Major Food Resource Pools in Lotic Systems
• Detritus CPOM FPOM
• Periphyton
• Macrophytes
• Prey
• What processes these and how?
• Shredders
• Collectors
• Scrapers Grazers
• Piercers
• Predators

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Role of Microbes
Fully conditioned
Conditioning
Time
3-4 weeks
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The influence of conditioning time of discs of
hickory leaves on utilization by Tipula
abdominalis. (From Allan, 1995)
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What is the Fate of Microbial Biomass?

• microbes metazoans macroinverts
  fish
• - major energy losses with each trophic level
• microbes
• 
  mineralization

Microbe Loop
link vs. sink debate
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What Consumes CPOM?

• amphipods (Gammarus)
• isopods
• crayfish
• freshwater shrimp
• snails
• Tipulidae (crane fly larvae)
• trichopterans

(wood consumers midges, elmids, caddisfly,
cranefly)
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FPOM Processors

• Captured from
• Suspension collectors-gatherers
• Substrate grazers scrapers

• Suspension Feeding Capture Mechanisms
• Setae on mouthparts or forelegs

Source Hynes (1972)
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1. Use of structures on the head

Source Hynes (1972)
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1. Catch Nets (esp. Trichoptera, some Chironomids)

Source Hynes (1972)
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1. Production of current through tubes

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FPOM Processors (continued)

• Deposit Feeding (grazers/scrapers)
• Feeding while burrowing
• - e.g., annelids
• Feeding on surface deposited particles
• - snails, stonefly (Brachyptera)

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Is temporal and spatial variability in substrate
food sources

• Some species are capable of
• - differential ingestion usually select
• higher of small particles
• - differential digestion
• e.g., high quality foods rapid absorption
• high feeding rates short GRT
• e.g., low quality foods slow
  absorption
• low feeding rates long GRT