1. STREAM
ECOLOGY

2. River Continuum Concept Model
Model for understanding and predicting changes within biotic communities of riverine ecosystems based upon geomorphic changes within those ecosystems
Specifically:
Energy flow / dynamics
Diversity / community assemblages

3. What is a model?
Predictive tool based on knowing something about the natural state
If we know something about an ecosystems natural state we should be able to predict the response of biological communities to changes in that natural state

4. Diversity

5. Diversity
Streams are dynamic systems whose biotic communities change with changes in
the physical (geomorphological) stream channel
e.g. width, depth, gradient
Chemical water quality
Riparian community
e.g. open, partially closed, closed

6. Stream Dynamics The River Continuum Concept -
Provides a framework within which we can understand and predict the responses of these dynamic biotic communities to their abiotic environments

7. River Continuum Concept Model

8. Diversity: headwater streams orders 1 to 3
Narrow with canopy cover nearly complete
Water temperature range (∆ T max) is small, only a few degrees
Diversity is low due to three primary factors:
A narrower/smaller range of optimum metabolic temperatures for organisms living there
Stream is largely homogeneous morphologically with few different habitats. (lateral vs main channel vs stream bank undercut
Energy sources are primarily allochthonous

9. River Continuum Concept Model

10. Diversity: middle stream orders 4 to 6
Have Maximum diversity due to three primary factors:
Increased range of optimum metabolic temperatures for organisms
Streams tend to be wider with more lateral habitats. More heterogeneous stream morphology
Increased trophic pathways provided by a combination riparian cover and open stream canopy

11. River Continuum Concept Model

12. Diversity: higher stream orders 7 +
Typically low diversity (lower than orders 4 - 6) for three primary reasons:
Light penetration is impeded by increased turbidity and increased depth of water decreasing primary productivity
Increased habitat homogeneity due to depth and width of river and sediment loads
Due to the reason above rivers tend to be reliant on FPOM coming from upstream

13. River Continuum Concept Model

14. Energy Flow

15. Energy Flow: stream orders 1 to 3
Riparian community is primary source of energy
Riparian cover provides energy input-CPOM
Typically nutrient poor:
Watershed energy comes from Allochtonous (out of stream) sources
Conditioned by fungi
Colonized by bacteria
Eaten by insects to get bacteria

16. Leaf litter enters stream
Colonized by hyphomycete fungi-
Fungi break though outside of leaf and open it up.
Bacteria colonize inside of leaf, feeding on the sugars inside
“Conditioning”
Shredders eat the conditioned leaf to get to the bacteria
Leaf pieces, bacteria, and feces sent downstream- FPOM available to collectors

17. Energy Flow: 1-3 order streams
P/R < 1
Benthic community composed primarily of shredders and collectors

18. Shredders Grazers Collectors
- organisms that take CPOM (Coarse, Particulate Organic Matter) and breaks it down into FPOM (Fine, Particulate Organic Matter)
Example: aquatic potato bug,
freshwater shrimp/scuds
Grazers
-Feed on plants
Example: algae/periphyton
Scrapers
Scrape rocks- ex: snails
Collectors
Organisms that typically catch FPOM and feet on it.
Ex: Midges

19. Energy Flow: Stream orders 4-6
Stream widens, light penetration is good due to low turbidity
Stream shifts from allochthonous (from outside) to autochthonous (from within) enegry sources. (i.e.- primary production)
1. P/R > 1= more productivity
2. Benthic community shifts from one dominated by shredders and collectors to one dominated by collectors and grazers (scrapers)

20. Energy Flow: stream orders 7 +
Stream gets deeper and wider, greater turbidity and decreased light  community shifts again
P/R < 1
Almost exclusively collectors and predators
Stream ecosystem downstream relies on FPOM from upstream sources to fuel downstream ecosystem
By destabilizing upstream through deforestation, we impact downstream Entire lower stream reliant on organisms that feed on FPOM
**What we do here has an impact further along
Ex: Delaware river