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Home > Lectures > Stream habitats

Stream habitats

I. Temperate Streams

A. Gradient - # of meters of drop per km of stream length (continuum) has a great effect on speed of water & hence on substrate & particulates

  1. High - fast streams, rocky bottom
    - streamlined species, see aquatic insects sheet

  2. Low - sluggish, muddy bottoms, still pool, particulates
    - deep bodied species (more agile @ maneuvering), se aquatic insects sheet

B. Stream regions

  1. Riffles - well oxygenated, moving water, gravel bottom

  2. Raceways - intermediate, moving water, sediment bottom

  3. Pools - still water, lower oxygenation, accumulate organic

II. Stream life

A. Primary production/carbon source

  1. Autochthonous - organic material originating in the water
    a. algae, diatoms, submerged (and emergent?) aquatic plants.
    b. low gradient streams

  2. Allochthonous - organic material added to a stream from outside
    a. leaves dropped in from overhanging trees
    b. high gradient streams

B. Riffle vs pool life

  1. Riffle organisms - must be able to resist the flow of the water of be swept away.
    a. Flattened or streamlined body shape
    b. Attachment devices: threads, suckers, building a home with glue & local materials
    c. Remaining out of the current by hiding under rocks.

  2. Pond organisms - must worry about low oxygen content and predation, rather than current flow.
    a. most burrow into the soft sediment
    b. predators hide in vegetation or cruise the water column
    c. many inhabitants have large gill structures of tubes for breathing from the surface

C. Animal groups

  1. Sponges

  2. Planaria (flatworms)

  3. Molluscs (clams, mussels, snails, limpets)

  4. Annelids (leeches)

  5. Arthropods
    a. Crustaceans - crayfish
    b. Insects
    i. larval aquatic insects (stonefly, dragonfly, midge, mosquito and other larvae
    ii. surface dwelling adult insects (water striders, water boatmen, backswimmers, diving beetles, etc.).

  6. Vertebrates
    a. Fishes
    b. Anurans (frogs)


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