Freshwater ecosystems 1 (lentic systems & key system drivers)

Question 1

ecological characteristics of freshwater ecosystems are largely determined by its ____ ___ and ____

• how?

Answer 1

heat budget: if covered by ice for >6 months, water column stabilizes (mixing in summer only)

topography: affects speed and inputs

Question 2

What are the 4 key features that exert strong ecological influences on freshwater systems?

Answer 2

1. persistent cold water temps
2. prolonged ice cover (= increased O2)
3. extreme seasonality of solar radiation
4. freeze-thaw cycles (drives erosion)

Question 3

dates of freeze-up and thaw influence:
- ___ availability
- gas ___
- ___ concentrations
- ___ exchange
- mixing

Answer 3

light
transfer
solute
heat

Question 4

Why does productivity tend to be low in freshwater systems?

Answer 4

-low nutrient input
- low temps, prolonged ice= short growing season

Question 5

describe the typical biota in freshwater systems

Answer 5

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)

Question 6

lentic=

• mixing or no?

Answer 6

“still” waters like lakes/ ponds

• no mixing! no O2 at bottom= layering of water based on density (temp)

Question 7

Lotic=

Answer 7

flowing waters like streams and rivers