Allochthonous Input

1
Allochthonous Input
2
Sources of organic matter

• Autochthonous instream
• Allochthonous out of stream

3
Allochtonous Energy

• Unappreciated Until the 70s
• May be the main source of energy

4
What happens to the organics?

• Allochtonous input primarily detritus
• Makes it hard to tell Autochtonous from
  Allochtonous

5
Types of organic matter

• Dissolved organic matter
• Soluble organic compounds
• Leach from leaves, roots, decaying organisms, and
  other sources
• Largest pool of organic matter in streams

• Particulate organic matter
• Coarse particulate organic matter
• Woody material leaves gt 1 mm
• Fine particulate organic matter
• Leaf fragments, invertebrate feces, and organic
  precipitates lt 1 mm

6
Size classes of detritus
7
Coarse particulate organic matter (CPOM)
8
Fine particulate organic matter (FPOM)
9
Dissolved organic matter (DOM)
10
Instream organic matter processing
The River Continuum - www.oaa.pdx.edu/CAE/Programs
/ sti/pratt/energy.html

• Routes carbon follows as it is processed within a
  stream.
• Microbes, macro-invertebrates, fish, and other
  organisms all play roles in the physical and
  chemical processing of organic matter.

11
Fate of organic matter

• Organic matter that enters streams may be
  (percent estimates are approximate and variable)
• Stored within the stream bank or channel (25)
• Exported downstream (50)
• Metabolized and respired as carbon dioxide by
  organisms (25)

12
Storage of organic matter

• Factors that are likely to increase retention
  time are debris dams, beaver dams, floodplains,
  and geomorphological features of the stream or
  river that impede flow.

13
Net primary production versus litter fall
Stream Autotochthonous Allochthonous
Bear Brook, NH 0.6 g C/m2/year 251 g C/m2/year
Silver Springs, FL 981 g C/m2/year 54 g C/m2/year
14
Bear Brook, New Hampshire

• Famous organic matter budget study
• (Likens, 1973).
• Small, forested headwater stream
• Greater than 99 of the carbon input came from
  allochthonous sources
• POM slightly greater than DOM
• Close to 65 of this input was exported downstream

• Input of DOM exceeded exports
• Due to leaf fall more POM was exported than
  entered the site

15
Fate of CPOM

• Best info for autumn-shed leaves
• Woody material is slower than leaves
• Other sources little studied
• Flower parts
• Feces
• Carcasses of large animals
• Macrophyte breakdown like terrestrial leaves

16
What factors influence leaf breakdown?
17
Rate of leaf breakdown

• Determined by
• Intrinsic differences among leaves
• Environmental variables
• Temperature
• Water chemistry
• Feeding activity of detritivores

18
Rate of leaf breakdown

• Modeled by
• Wt dry mass at time t
• Wi initial dry mass
• t measured in days
• k is the slope of the plot of loge of leaf mass
  versus time

19
Comparison of Breakdown Rates
20
Breakdown rates for various woody and non-woody
plants
1/2 life in days

• 596 estimates from field studies
• Variation due to
• Site
• Technique
• Environmental variables

Non-woody
woody
21
What factors might facilitate breakdown?
22
Stages in breakdown of autumn leaves

• Leaves fall into stream
• Become wetted
• Begin leaching organics inorganics
• 25 of initial dry mass lost in 24 hrs
• Soluble carbohydrates
• polyphenols
• Colonization by microbial organisms
• Bacteria
• fungi
• Fragmentation
• Mechanical
• Biotic activity primarily invertebrates

23
What factors might influence Microbial processing
of stream captured leaves?
24
Microbial processing of stream captured leaves

• If nutrient is high, breakdown is faster
• High lignin slows breakdown
• Lignin
• strengthening material that occurs with cellulose
  and other polysaccharides in cell walls
• 2nd most abundant organic compound on earth
• Insoluble, high molecular wt., made of 3 aromatic
  alcohols
• In living plant also gives resistance to attack
  by pathogens and consumption by herbivores
• Chemical inhibitors in leaves slow breakdown
• Allelochemics isoprenoids ( terpenoids or
  terpenes)
• Anti-herbivore and allelopathic compounds
• Tannins bind proteins, make them harder to digest
• Tannins are anti-microbial (as are many
  phenolics)
• Waxy cuticle inhibits breakdown

25
Processing sequence for aleaf in a temperate
stream
26
Time course of leaching of soluble organics
(DOM) from elm and alder leaves
Elm-10oC Elm-20-22 oC
Alder-10oC Alder - 20-22oC
27
And now for a global warming question?

• If temperature affects breakdown, what will
  happen if it gets warmer?
• If species differ in breakdown time, what will
  happen as species move north or disappear?

28
What is Succession?
29
Successional Ecology Fungi

• Fungi (aquatic hyphomycetes) dominate in the
  early fall as leaves enter stream
• Which ever fungal spores attach first wins

30
Successional Ecology Bacteria

• Bacteria dominate the terminal processing
• Bacteria benefit by fungal conditioning of leaf

31
Successional and Feeding

• Nutritional value of leaf declines after a few
  weeks in the stream
• Decomposition and thus nutritional value to a
  detritivore is variable good choosers get a
  better meal

32
What do decomposers require to function?
33
Impact of Microbes on Leaf Breakdown
34
Influence of Detritivores fragmentation

• Why does fragmentation matter?

35
Influence of Detritivores fragmentation

• Leaf packs in mesh bags decomposed more slowly
  than those without bags
• Mesh size excluded detritivores
• Breakdown rates are higher when inverts are more
  abundant
• Up to 25 of leaf degradation attributable to
  animals
• Direct consumption
• Release of nutrients and DOM
• Comminution (to break or crush into powder) of
  litter
• Modification of water circulation

36
Influence of Detritivores fragmentation

• Up to 25 of leaf degradation attributable to
  animals
• Direct consumption
• Release of nutrients and DOM
• Comminution (to break or crush into powder) of
  litter
• Modification of water circulation

37
General organic matter pathway
38
Who are the primary leaf litter detritivores

• Plecoptera Stoneflies
• Pteronarcys sp.

From Merritt Cummins, 1996
39
Who are the primary leaf litter detritivores ?
From Wiggins, 1978
Tricoptera caddis flies Pycnopsyche sp.
40
Who are the primary leaf litter detritivores?
From Merritt Cummins, 1996
Diptera Tipulidae crane flies Tipula sp.
41
Suppression of detrital activity slowed loss in
leaf mass
42
FPOM

• Even less know than CPOM
• Comes from both CPOM DOM\
• Spores, Feces etc.
• Primary source other than leaves
• Most like soil OM
• Bacteria Dominate decomposition

43
DOM

• Typically largest pool of C in lotic systems
• But often low bioavailability

44
Carbon fluxes in a stream ecosystem
45
Water on the Web

• This presentation includes material from Water on
  the Web (WoW)
• WOW. 2004. Water on the Web - Monitoring
  Minnesota Lakes on the Internet and Training
  Water Science Technicians for the Future - A
  National On-line Curriculum using Advanced
  Technologies and Real-Time Data.
• http//WaterOntheWeb.org).
• University of Minnesota-Duluth, Duluth, MN 55812.
• Authors Munson, BH, Axler, R, Hagley C, Host G,
  Merrick G, Richards C.
• I would also like to thank Dr. Jewett-Smith for
  her contributions to this presentation