1. Chapter 1.3 Stream Biology

2. There are 3 dominant groups of organisms in most stream communities.
Algae and Animal like protists
Invertebrates
Vertebrates

3. Are plantlike protists that make their own food (autotrophs)
Algae
Are plantlike protists that make their own food (autotrophs)
Since they are autotrophs it forms the base of most aquatic food chains.
Freshwater Alage use sunlight and dissolved nutrients in a stream to make their food.
Animal-like protists
Has many characteristics as animals
Are aquatic organisms that eat:
Bacteria
Sediments that contain bacteria
Ex. Ameoba, Euglena

4. Amoeba Raptors Saprotrophs
Are protists that engulf food by flowing around and over it
Raptors
Protists that eat other protist
Saprotrophs
Protists that feed on decayed organic material

5. Invertebrates Do not have an internal skeleton made of bone
Examples of freshwater invertebrates
Insects, worms, mollusks
Shredders & striders
Mollusk
strider
Mollusk

6. Vertebrates Has an internal skeleton made of bone
Examples of freshwater Vertebrates
amphibians (frogs, salamanders)
fish

7. Factors that affect Freshwater ecosystems
Stream order
Smaller streams ( 1st order) flow into larger streams (2nd order) and continue on. Two streams of the same
order must come together for a stream to move up
in order.
The size or order of the stream relates directly on the organisms that are in the ecosystem.
1st order streams are home to large insect populations, few if any fish.
Plants and game fish dominate 3rd & 4th order.
Larger the stream the more diverse populations of algae, fish, and other aquatic organisms.

8. Factors that affect Freshwater ecosystems
Temperature
Change in temp affects the kinds and #’s of species in a stream.
Some species can live in a wide range of temps (catfish and carp), while others species can survive only in certain temps (algae, protists and trout).
Examples of factors that causes difference in stream temp
Velocity
Depth
Seasonal change
Riparian coverage

9. Factors that affect Freshwater ecosystems
Current
Unidirectional
Causes different forces on organisms in the stream
Velocity
Change in distance over time.
Fish are unaffected by velocity, while insects are generally limited to calmer water.
Waters moves the fastest in the middle of the stream below the surface.
Substrate
Is the material that organisms live in, on, or around.
EX. of Organic substrate – algae, plants, mosses
EX. of Inorganic substrate – rocks, sand, silt and mud

10. Factors that affect Freshwater ecosystems
Sunlight (plants rely on it to make food thru photosynthesis)
Less sunlight = less organisms
Turbidity (clarity)
Reflects the amount of suspended matter in water
Facts that affect turbidity
Increase in stream erosion
Increase in water volume
Heavy rain/melting snow

11. Factors that affect Freshwater ecosystems
Dissolved Gases
Oxygen and Carbon dioxide
Oxygen
Enters the water from the air
Concentration depends mainly on temp
As temp increases, D.O. decreases
Photosynthesis also adds oxygen to the water
Current
As current decreases, so does D.O.

12. Factors that affect Freshwater ecosystems
Organic Matter
Mostly used for food
Algae and detritus (particulate organic matter)
Too few nutrients = loss of organisms
Too many can cause mass algal blooms and then loss of other organisms pH
Scale ranges 0-14, 7 neutral, below 7 acidic, above 7 basic
Rainwater tends to be slightly acidic
Mine drainage is a major contributor to stream acidification