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CXB Ecological Systems > Test 2.1 Freshwater Ecosystems > Flashcards

Test 2.1 Freshwater Ecosystems Flashcards

1
Q

Key 8 physical and chemical properties of freshwater ecosystems include:

A
  • Density, viscosity
  • Flow, velocity and depth
  • Light
  • Temperature
  • Dissolved Oxygen
  • Carbon dioxide
  • pH
  • Nutrients
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2
Q

% Proportion of ocean water of all water

A

around 97%

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3
Q

% Proportion of freshwater of all water

A

around 3%

2.15% of which is glaciers

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4
Q

6 physical challenges of living in freshwaters?

A 
Physical medium of water
Buoyancy
Density
Viscosity
Temperature
Salinity
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5
Q

What is viscosity?

A

The resistance of a fluid to shear stress - ‘thickness’ or ‘drag’

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6
Q

What is Reynold’s number?

A

Ratio of inertial forces (opposing current forces) to viscous forces ‘roughness’

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7
Q

What increases roughness/ Reynold’s number?

A

Size and velocity

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8
Q

Water properties important for large objects?

A

Pressure

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9
Q

Water properties important for medium objects?

A

Pressure and drag

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10
Q

Water properties important for small objects?

A

Drag and viscosity

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11
Q

Increase in discharge and flow down the hydrological system due to?

Why are the proportions important?

A 
Greater amount of inputs:
Direct runoff
Ice melt
Groundwater
etc.

Temperature and nutrient levels are due to where its from- affects organisms present

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12
Q

What are Lotic systems?

A

Flowing systems - rivers

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13
Q

What are Lentic systems?

A

Standing systems - Lakes

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14
Q

Why is flow important in freshwater ecosystems?

A

Organisms are adapted to velocity and shear stress

Provides nutrients

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15
Q

List hydraulic variables

A

Velocity
Shear stress
Water depth- more important in lakes

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16
Q

Why is depth more important in lakes?

A

Temperature- Deep lakes with limited flow proceed strong patterns, effects nutrients

Light- source of energy for organisms

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17
Q

What determines the temperature of water? (6 reasons)

A

Origin & inputs- groundwater, glacier e.g.
Air temperature
Season
Time of day
Water depth and discharge
Substrate and amount of turbulence (mixing)

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18
Q

Hyporheic zone meaning

A

Below the river bed zone containing water

Exchange of groundwater to surface water- affects temperature

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19
Q

Why is water temperature less variable than air temperature?

A

Due to water’s high specific heat capacity

20
Q

What are the two forms of ice found in rivers?

A

Frazil ice- mobile first particles that form on the surface of the water

Anchor ice- Ice frozen in solid connection with the banks, spreads across the rest of the river surface

21
Q

What is the coolest source in order:
Surface run off
Glacial
Karstic - what is it?

A

Average coolest temperature:

  1. Glacial
  2. Karstic (high proportion from groundwater & most stable)
  3. Surface run off snow melt (most variable)
22
Q

How does variability and average water temperature vary downstream?

A

Average temp increases as you go downstream

Variability is greatest in smaller streams

Larger rivers are more stable due to greater size and buffering capacity

23
Q

How does topography and vegetation affect water temperature?

A

Cooling effect due to shading and evapotranspiration

24
Q

What is the long term trend of average temperature in large rivers (Mississippi; Trent)

What are the causes?

A

Increased even though air temperature recorded was 2.2 degrees cooler.

Mississippi: Warming due to industrial warm effluents.

Trent: Cooling due to closed coal power stations no longer produce water effluent for cooling

25
Q

How does temperature effect Salmon?

A

Salmon develop in warmer conditions. Very warm conditions can be damaging.

26
Q

How does temperature effect Mayflies?

A

Speed of development and timing of hatching is temperature dependent. Fast summer generation, slow winter generation

27
Q

Definition of Univoltine & bivoltine?

A

Univoltine: Single generation period per year
Bivoltine: 2 generations per year

Often in tropical rivers there are more multivoltine species

28
Q

What effects dissolved oxygen in river water?

A

Increase:
Photosynthesis
Turbulence

Decrease:
Respiration (decomposers - microorganism’s)

29
Q

How does temperature affect oxygen levels?

A

High temperature results in lower oxygen

30
Q

How does altitude affect oxygen level?

A

Water at sea levels can hold more oxygen than at altitude

31
Q

What is the ecological significance of dissolved oxygen in salmon, trout and tench?

A

Salmon and trout need high levels of oxygen

Tench more tolerant of lower oxygen levels

32
Q

What concentration of oxygen is required for salmon eggs to survive and develop?

A

5mg/L

33
Q

How are invertebrate species adapted to low oxygen levels?

A

Gills on body
High haemoglobin content

Caddis have gills along body, can create current to bring o2 to gills

34
Q

How does pollution affect dissolved oxygen?

A

Organic sewage broken down using respiration & therefore oxygen.

35
Q

Hows does carbon dioxide affect water quality?

A

Dissolves to form carbonic acid - disassociation reduces to produce hydrogen ions - raises pH

36
Q

How does temperature affect CO2 levels?

A

Higher temperature means higher CO2 levels

37
Q

How does limestone & chalk affect buffering capacity?

A

Rich in natural carbonates and bicarbonates, buffered against acidity due to high pH

38
Q

How many microequivalents per litre are required for a residual buffering capacity?

A

120me/L and above

39
Q

What are the changes of alkalinity in a diurnal pattern?

A

Low natural alkalinity with vegetation present tend to find pH rises in afternoon with increase in photosynthesis

40
Q

List essential nutrients for plant growth

A

Main:
Nitrogen
Phosphorus

Other:
Calcium
Iron
Manganese
Magnesium
Potassium
Silica
Sodium
41
Q

Where does nitrogen come from in a river?

A

Atmospheric nitrogen fixed by nitrogen fixing microorganisms into ammonium

Decomposition of organisms. Ammonium then through nitrification to nitrite to nitrate

42
Q

Where does phosphorus come from in a river?

A

Taken up in plants, consumed by animals, broken down and released by bacteria into inorganic phosphorus.

Closed cyclic system

43
Q

Name the globally most important limiting element

A

Phosphorus

Sometimes silica

44
Q

What is the natural ratio of N:P?

A

N:P
16:1

45
Q

What its the effect of nitrogen and phosphorus pollution?

A

Pollution raising nitrogen no significant effect

Pollution raising phosphorus where there is abundant nitrogen has significant effects

CXB Ecological Systems (11 decks)

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