Freshwater habitats

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• Fresh-water habitats
• 1. Lentic standing-water (lenis calm)
• 2. Lotic running-water (lotus washed)
• Six principal factors influencing the success of
  aquatic organisms.

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• 1. Temperature
• H2O unique thermal properties
• H2O minimizes temperature changes
• Range of variation smaller
• Changes occur more slowly in H20 than air
• relative large amount of heat required to change
  H20 temperature
• Large amounts of heat are absorbed by H20 during
  evaporation
• occurs more or less continuously from surfaces of
  water and ice
• Greatest density at 4o C.
• H20 expands and becomes lighter both above and
  below this temperature.

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• Temperature becomes limiting if aquatic organisms
  have narrow tolerances
• Temperature produces characteristic patterns of
  circulation and stratification which influence
  aquatic life in lentic systems.
• 2. Transparency
• Turbidity (suspended materials) can limit light
  penetration, hence photosynthesis
• affect filter feeders

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• 3. Current
• Water is dense
• challenge to move through it
• moving H20 can displace many organisms,
  particularly in streams
• 4. O2 concentration
• air has c. 21 oxygen
• lt 15 parts/million O2 in water at just above
  freezing.
• 5. Concentration of nutrients
• Nitrates and phosphates elevated in nearly all
  natural fresh-H20 ecosystems
• 6. Current velocity
• molds the character of the stream.

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Ecological classification of fresh-H20 organisms

• 1. Non-taxonomic classification based on
  position in energy fixation (food chain)
• A. producers
• B. consumers
• C. decomposers
• Will generally identify the major dominants

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Freshwater ecosystems

• 1. Lotic ecosystems
• Flowing water derived from a watershed a body
  of land bounded above by a ridge.
• The land area contributing to one stream is its
  basin.
• Classification of streams
• 1st order stream a small headwater stream
  without tributaries
• Two or more streams of the same order join to
  produce a stream of a higher order (1-3, 4-6, gt6)

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A watershed
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Various habitats
Pool
Riffles Highest production
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• Vertical zones of streams
• 1. surface
• 2. water column
• 3. benthos
• Horizontal zones
• 1. wetted channel (perrenial H2O)
• 2. active channel (floods /- annually)
• 3. flood plain with riparian vegetation.

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• Primary production in streams can be
• 6-30 times that in lentic systems
• Renewal of nutrients and producers from upstream
• Beneficial to /- continuous processes such as
  photosynthesis

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Fast Current
Slow Current
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Stream Continuum
GT 1
LT 1
DOM LT 0.5 micrometer IS
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Index of water quality Wabash River
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• For freshwater ecosystems, consumers can be
  classified based on life form.
• A. Benthos bottom organisms
• B. Periphyton organisms attached to or clinging
  to surfaces projecting above the bottom
• C. Plankton floating organisms whose movements
  are dependent on currents
• D. Nekton swimming organisms able to navigate
  at will (i.e., against currents)
• E. Neuston organisms resting or swimming on the
  surface

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• Sub-habitats in lentic ecosystems
• 1. Littoral zone shallow H20 with light
  penetration to the bottom (typically occupied by
  rooted plants).
• 2. Limnetic zone open H20 zone to the depth of
  effective light penetration
• 3. Profundal zone H20 beyond the depth of
  effective light penetration.

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• Two other zones are recognized in shallow
  streams
• 1. Rapids zone
• shallow H20 where velocity of current is
  sufficient to keep bottom clear of silt and other
  debris
• occupied by specialized benthic and periphytic
  organisms
• 2. Pool zone
• deeper H20 where current velocity is reduced
  silt, etc. tends to settle to the bottom
• bottom occupied by specialized burrowers

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• Lentic ecosystems
• Lakes ponds inland depressions containing
  standing water
• Natural basins formed from glacial, volcanic, and
  tectonic activity

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Glacial lake
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Glacial lakes (potholes)
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Oxbow lakes
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Caldera or crater lake
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Habitat zones

• Four to remember
• Littoral
• Limnetic
• Profundal
• Benthic

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Profundal