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CXB Ecological Systems > Test 2.1 Lakes > Flashcards

Test 2.1 Lakes Flashcards

1
Q

What 7 characteristics would you use to describe a lake?

A 
Length
Width or breadth
Depth: max or mean
Shoreline (L)
Volume
Retention or residence time
Light availability
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2
Q

How do you calculate residence time?

A

Volume / mean rate of inflow
or
Mean rate of outflow + evaporation rate

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3
Q

How are tectonic lakes formed?

A

When 2 plates move apart creating a Rift Valley

e.g. Lake Baikal, Siberia, oldest in the world, 1620m deep

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4
Q

What are the characteristics of Lake Baikal?

A 
Oldest lake in the world
L=636km
W=80km
L (shoreline)=2100km
D=1620M

3 depressions with total volume of 23,600km^3
>20% world’s surface freshwater
1200 species of animals
1000 species of plants

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5
Q

How are glacial lakes formed?

A

Formed in last ice age

Glacier dredges the bottom of the valley creating a bowl

Or deposited moraine blocks a stream, forming a lake

Kettle lakes formed by melting ice blocks

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6
Q

How are thermokarst lakes formed?

A

Permafrost thawing to create shallow surface tundra lakes

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7
Q

How are oxbow lakes formed?

A

Large meanders in rivers join up and cut off the old river path

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8
Q

Reasons for building man made lakes?

A

Hydro power e.g. Lake Powell, Hoover Dam

Water supply/ flood storage

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9
Q

Meaning of Lotic

A

Flowing - rivers

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10
Q

Meaning of Lentic

A

Standing - lakes

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11
Q

What variables are significant in lakes?

A

Depth for:

  • Light penetration
  • Temperature regime

Distinct seasonal patterns in temperature & water chemistry

Current velocity less significant

Autochtonous production more important than allochthonous production

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12
Q

What is lake temperature stratification?

A

Summer air temperatures warming the upper layers of lakes separates the upper layer of water from the lower colder layer.

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13
Q

What is the name of the upper warmer surface layer of a lake?

A

Epilimnion - well oxygenated

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14
Q

What is the name of the deeper cooler layer of a lake?

A

Hypolimnion - oxygen depleted

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15
Q

What is the name of the distinct separation of layers between upper warmer water and deeper cooler water?

A

Thermocline

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16
Q

Why is the separation of water layers important?

A

In summer they can become separated:

Stops oxygen moving from surface to deeper layers- depleted
Prevents nutrients from lower layers reaching the upper layers- depleted

In cold regions the temperature of layers is the opposite

Mixing occurs in spring and autumn

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17
Q

Definition of Holomictic lakes

A

mixed all year. Never form epilimnion or thermocline

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18
Q

Definition of Monomictic

A

Lakes that mix once per year

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19
Q

Definition of warm Monomictic

A

Lakes that stratify in summer, mixed in winter

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20
Q

Definition of Dimictic

A

Lakes that stratify in both winter and summer, mix in autumn and spring

21
Q

Definition of Meromictic

A

Lakes that never mix

22
Q

How does warmer waters affect deepwater fish species and oxygen levels?

A

Lake stratification creates a greater contrast between the two layers, reducing the oxygen mixing to the deepest parts therefore fish cannot survive

23
Q

What are the limiting factors for producers in lakes?

A

Nutrients: phosphorus & nitrogen

Light: Transparency (turbidity and colour) determines light

24
Q

What interferes with light penetration?

A

Colour- (dissolved substances)
coloured lakes less productive

Turbidity- suspended particles
plankton will also limit light reaching bed

25
Q

What do you use to measure nutrients and light penetration?

A

Van Dorn sampler (tube)

Secchi disc for transparency- measure how deep before not visible

26
Q

What is an Oligotrophic lake?

A
  • Nutrient poor
  • Low productivity
  • High transparency in epilimnion
  • High dissolved oxygen in hypolimnion
27
Q

What is a Mesotrophic lake?

A

middle rich?.?.?

28
Q

What is a Eutrophic lake?

A
  • Nutrient rich
  • High productivity
  • Low transparency in the epilimnion
  • Low dissolved oxygen in the hypolimnion
29
Q

What is benthic algae?

A

Algae on the lake bed

30
Q

What is planktonic algae?

A

Algae living in the open water e.g. diatoms

31
Q

What are macrophytes?

A

Rooted aquatic plants e.g. Litorella ‘shore weed’

32
Q

What are zooplankton?

A

Microscopic animals feeding on phytoplankton and other zooplankton

33
Q

What are phytoplankton?

A

Some are filamentous algae

Some diatoms- single cells or in colonies (require silica)

34
Q

Name some consumers

A

Mayfly
Chironomidae
Pond snail
Freshwater limpet

35
Q

Name some predators

A

Waterfleas
Phantom midge larva
Roach fish

36
Q

What are keystone species. Give examples

A

Species that have particular importance within a community

Gwyniad fish
Perch and Ruffe fish

37
Q

Give an example of a dominant lake species

A

Chronomidae

38
Q

What are the winter patterns of phytoplankton?

A

Lake is well mixed but plankton abundance low, limited by light and temperature

39
Q

What are the spring patterns of phytoplankton?

A

Plankton increase and use up nutrients

40
Q

What are the summer patterns of phytoplankton?

A

Lower plankton abundance, limited by nutrients

41
Q

What are the autumn patterns of phytoplankton?

A
  • First storms
  • Mixing
  • Thermocline breaks up
  • Plankton exploit newly available nutrients
42
Q

What is the adaptation of water scorpions

A

Breathing tubes

43
Q

What is the adaptation of Phantom midge larvae

A

Buoyancy

44
Q

What is the adaptation of Water Measurer

A

Long legs to walk on water

45
Q

What is the adaptation of Water Boatmen

A

Traps air

46
Q

What is the adaptation of Chironomidae

A

Haemoglobin type pigment

47
Q

What is the Euphotic depth?

A

Depth where photosynthesis is possible

  • limits phytoplankton depth
  • limits growth of rooted plants and benthic algae
48
Q

What is the Littoral zone?

A

Lake bed where plants can grow

49
Q

What is the Profundal zone?

A

Lake bed where there is no plant growth

CXB Ecological Systems (11 decks)

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