Freshwater ecosystems 1 (lentic systems & key system drivers)
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ecological characteristics of freshwater ecosystems are largely determined by its ____ ___ and ____ • how?
heat budget: if covered by ice for >6 months, water column stabilizes (mixing in summer only) topography: affects speed and inputs
What are the 4 key features that exert strong ecological influences on freshwater systems?
• persistent cold water temps • prolonged ice cover (= increased O2) • extreme seasonality of solar radiation • freeze-thaw cycles (drives erosion)
dates of freeze-up and thaw influence: - ___ availability - gas ___ - ___ concentrations - ___ exchange - mixing
light transfer solute heat
Why does productivity tend to be low in freshwater systems?
-low nutrient input - low temps, prolonged ice= short growing season
describe the typical biota in freshwater systems
in response to low productivity: slow growth, some longer-lived organisms - adapted tolerance of low temp - rapid conversion of food to lipid storage - some are migratory (triggered by enviro cues)
lentic= • mixing or no?
“still” waters like lakes/ ponds • no mixing! no O2 at bottom= layering of water based on density (temp)
Lotic=
flowing waters like streams and rivers