1. Allochthonous Input

2. Sources of organic matter
Autochthonous – instream
Allochthonous – out of stream
/streamwatch/ swm10.html
manual/6doing.htm
veg/brfredmaple.html
Autochthonous organic matter – produced within the stream
- diatoms; algae; submerged, floating, and emergent macrophytes
Allochthonous organic matter – produced outside of the stream and imported into the channel.
- includes, but is not limited to leaves, woody debris, dissolved organic compounds, dead organisms

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. Size classes of detritus

6. Coarse particulate organic matter (CPOM)

7. Fine particulate organic matter (FPOM)

8. Dissolved organic matter (DOM)

9. Fate of organic matter Stored within the stream bank or channel (25%)
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%)
Photo – g. merrick
Organic matter that enters streams may be (percent estimates are approximate and variable):
1) stored within the stream bank or channel (25%)
2) exported downstream (50%)
3) metabolized and respired as carbon dioxide by organisms (25%)

10. 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.
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.

11. Net primary production versus litter fall
Net primary production is far greater in open compared to closed canopy streams, but the relative contribution of energy by primary production and litter fall to an ecosystem’s energy is also influenced by climate and nutrient availability.
Data from selected from Table 12.5 in Allan, J.D., 1995
do/page3.html
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

12. Bear Brook, New Hampshire
Famous organic matter budget study
(Likens, 1973).
Small, forested headwater stream
Bear Brook in New Hampshire is the site of a famous organic matter budget study (Likens, 1973). In the this small, forested headwater stream it was found that greater than 99% of the carbon input to Bear Brook came from allochthonous sources (POM slightly greater than DOM). Close to 65% of this input was exported downstream from the 1700 meter long study site.
Input of DOM exceeded exports
Due to leaf fall more POM was exported than entered the site

13. Primarily Allochthonous Energy
>99% of the carbon input from allochthonous sources
POM slightly greater than DOM
Close to 65% of this input was exported downstream
Bear Brook in New Hampshire is the site of a famous organic matter budget study (Likens, 1973). In the this small, forested headwater stream it was found that greater than 99% of the carbon input to Bear Brook came from allochthonous sources (POM slightly greater than DOM). Close to 65% of this input was exported downstream from the 1700 meter long study site.
Input of DOM exceeded exports
Due to leaf fall more POM was exported than entered the site

14. 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

15. What factors influence leaf breakdown?

16. Rate of leaf breakdown Determined by
Intrinsic differences among leaves
Environmental variables
Temperature
Water chemistry
Feeding activity of detritivores

17. 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

18. What characteristics of leaves might reduce the rate of Microbial Processing?

19. High [lignin] slows breakdown
strengthening material that occurs with cellulose and other polysaccharides in cell walls
Second 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

20. 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)

21. Waxy cuticle inhibits breakdown

22. Breakdown Rates By Species

23. 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

24. Global climate change questions
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?

25. Stages in breakdown of autumn leaves
Leaves fall into stream
Begin leaching organics & inorganics
25% of initial dry mass lost in 24 hrs
Soluble carbohydrates
polyphenols

26. Elm-10oC
Elm oC
Alder-10oC
Alder oC
Time course of leaching of soluble organics (DOM) from elm and alder leaves

27. Stages in breakdown of autumn leaves
Colonization by microbial organisms
Bacteria
Fungi
Fragmentation
Mechanical
Biotic activity: primarily invertebrates

28. Processing sequence for a leaf in a temperate stream

29. What is Succession?

30. Successional Ecology: Fungi
Fungi (aquatic hyphomycetes) dominate in the early fall as leaves enter stream
Which ever fungal spores attach first wins

31. Successional Ecology: Bacteria
Bacteria dominate the terminal processing
Bacteria benefit by fungal conditioning of leaf

32. 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

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

36. Up to 25% of degradation due to animals
Direct consumption
Release of nutrients and DOM
Comminution of litter
to break or crush into powder
Modification of water circulation

37. Suppression of detrital activity slowed loss in leaf mass

38. Carbon fluxes in a stream ecosystem
Figure 12.1
Processing of organic matter in streams, whether autotochthonous or allochthonous, is largely carried out by macroinvertebrates and microbes. Carbon not assimilated is exported and carbon that is respired is exported or evolved back to the atmosphere.
Figure 12.1 Simplified model of principal carbon fluxes in a stream ecosystem. Solid lines indicate dominant pathways of transport or metabolism of organic matter in a woodland stream. R-circle denotes mineralization of organic carbon to carbon dioxide respiration. (Modified from Wetzel, 1983)

39. Who are the primary leaf litter detritivores
Plecoptera: Stoneflies
Pteronarcys sp.
From: Merritt & Cummins, 1996

40. Who are the primary leaf litter detritivores ?
From: Wiggins, 1978
Tricoptera:
caddis flies
Pycnopsyche sp.

41. Who are the primary leaf litter detritivores?
From: Merritt & Cummins, 1996
Diptera: Tipulidae = crane flies
Tipula sp.

42. FPOM: Spores, Feces etc. Even less know than CPOM
Comes from both CPOM & DOM
Primary source of energy other than leaves
In deciduous forest
Similar to 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
Figure 12.1
Processing of organic matter in streams, whether autotochthonous or allochthonous, is largely carried out by macroinvertebrates and microbes. Carbon not assimilated is exported and carbon that is respired is exported or evolved back to the atmosphere.
Figure 12.1 Simplified model of principal carbon fluxes in a stream ecosystem. Solid lines indicate dominant pathways of transport or metabolism of organic matter in a woodland stream. R-circle denotes mineralization of organic carbon to carbon dioxide respiration. (Modified from Wetzel, 1983)

45. Water on the Web
This presentation includes material from Water on the Web (WoW)
WOW 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.
University of Minnesota-Duluth, Duluth, MN
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