Overwiev of Lake Ecosystems

Question 1

What is a lake?

Answer 1

A slowly flowing or non-flowing (lentic) open
body of water in a depression and not in
contact with the ocean.

Question 2

Which lake is the largest lake?

Answer 2

Lake Victoria (Africa) is the largest lake in terms of surface area, but Lake Baikal (Russia) is the largest lake in terms of volume.

Question 3

They are 9 types of lakes, mention 3.

Answer 3

• Tectonic lakes
• Volcanic lakes
• Glacial lakes
• Earthslide lakes
• Sinkhole lakes
• Fluvial (oxbow) lakes
• Aeolian lakes
• Crater lakes
• Animal-created lakes

Question 4

What type of lakes are some of the oldest, deepest, and most
ecologically and evolutionarily unique lakes.

Answer 4

Tectonic lakes

Question 5

How are tectonic lakes formed?

Answer 5

Tectonic movements of the earths crust.

Question 6

There are 2 type of tectonic lakes, what are they?

Answer 6

• Graben Lakes – multiple faults allow a block to
  drop down and form a depression (e.g. Lake
  Biakal)
• Horst Lakes – single fault tips down, forming a
  depression (e.g. Owens Valley)

Question 7

What is the main characteristics of volcanic lakes?

Answer 7

Characterize by having really abnormal abiotic frames because of earlier volcanic activities in the area.

Question 8

Which lake type is the most abundant?

Answer 8

Glacial lakes.

Question 9

What are the 2 characteristics of glacial lakes?

Answer 9

They are mainly found in temperate regions, and they are young lakes.

Question 10

There are 3 types of glacial lakes, what are they?

Answer 10

Those formed by glacial scouring
Those formed by glacial deposits
Those formed by the release of large volumes of water from behind ice dams

Question 11

Kettle lakes are glacial lakes, how are they formed?

Answer 11

1. Receding glacier leaves dead ice.
2. Glacial outwash (sand) is deposited.
3. When the ice melts, they form depression with water, forming lakes.

Question 11

How are fluvial (oxbow) lakes formed?

Answer 11

They are formed when rivers change their shapes through erosion, and over time the swirly part of the river gets cut off forming banana shaped lakes.

Question 12

How are aeolian lakes formed?

Answer 12

They are formed by wind

Question 13

Name 2 animals that can form lakes.

Answer 13

Beavers, human.

Question 14

Draw lake habitats, you have to include:
- Littoral zone
- Limnetic/ pelagic zone
- Benthic zone
- Photic zone
- Profundal (aphotic) zone

Question 15

Name the 3 lake productivity types.

Answer 15

• Oligotrophic
• Mesotrophic
• Eutrophic

Question 16

What is an oligotrophic lake?

Answer 16

Oligotrophic – nutrient-poor, low primary production, often deep with low shoreline development.

Question 17

What is a mesotrophic lake?

Answer 17

Moderately productive lake.

Question 18

What eutrophic lake?

Answer 18

Eutrophic – nutrient rich, high primary production, often shallow with high shoreline development.

Question 19

Draw lake stratification. You have to include:
- Epilimnion
- Metalimnion/thermocline
- Hypolimnion
You also have to include how it will look during winter, spring, summer, and autumn.

Question 20

They are 2 types of wind affect of mixing of lakes, what are they?

Answer 20

• Langmuir cells - Langmuir cells created by strong, sustained winds (gray arrows). Dark blue arrows show the movement of surface water as a result of the cells, producing downwelling convergence zones where floating material can accumulate (gray shading), and upwelling divergence zones.
• Seiche - when wind tilts the thermocline.

Question 20

There are 4 lake mixing types, what are they?

Answer 20

• Dimictic – mixes twice per year, common in temperate and arctic regions where ice cover is present in winter
• Monomictic – mixes once per year, common in temperate regions where no ice cover forms
• Polymictic – mixes several times per year, common in tropical regions
• Meromictic (amictic) – do not mix, present in tropical regions, may contain dissolved compounds in hypolimnion that stabilize the density layers (e.g. the Dead Sea did not mix for 300 years)