Stratification

Question 1

Epilimnion

Answer 1

Top layer of water in the summer where sunlight and turbulence due to the wind causes good mixing.

Question 2

Hypolimnion

Answer 2

In the summer, turbulence does not penetrate lower, hence a poorly mixed stratified layer of cooler water.

Question 3

Thermocline

Answer 3

The layer separating the epilimnion and the hyplimnion.

Question 4

Autumn

Answer 4

When the temperature drops, the epilimnion cools and sinks causing overturning and complete mixing.

Question 5

Winter

Answer 5

Mixing stops at 4 degrees. Further cooling or freezing on the surface results in winter stratification.

Question 6

Monomictic

Answer 6

One cycle of stratification

Question 7

Dimictic

Answer 7

Two cycles of stratification

Question 8

Menomictic

Answer 8

No cycles of stratification

Question 9

Polymictic

Answer 9

Many cycles of stratification

Question 10

Euphotic Zone

Answer 10

This is a well lit zone at the upper layer allowing plant growth. Depth depends of turbidity and algae present.

Question 11

Profundal Zone

Answer 11

Where light cannot penetrate (light intensity is 1% of unattenuated sunlight).

Question 12

Light compensation level

Answer 12

The transition between the euphotic zone and the profundal zone.

Question 13

Littoral zone

Answer 13

The shallow water near to the shore in which rooted plants can grow.

Question 14

Benthic Zone

Answer 14

Bottom settlements. Dead organisms settle to the benthic zone to decompose. Bacteria is always present. The presence of higher life forms depends on oxygen availability.

Question 15

Oligotrophic

Answer 15

Lakes with low productivity. They tend to be saturated with oxygen and dominated by trout and whitefish.

Question 16

Lake Productivity

Answer 16

The ability of a lake to support a food web.

Question 17

Eutrophic

Answer 17

Lakes with high concentrations of nutrients and a resultant high biomass production and poor transparency. The lake can only support warm water fish such as perch and roach because the hypolimnion in the summer become anaerobic.

Question 18

Mesotrophic

Answer 18

Lakes on the transition between oligotrophic and eutrophic containing whitefish and perch.

Question 19

Ultra-oligotrophic

Answer 19

Extremely low nutrient lake.

Question 20

Hyper-eutrophic

Answer 20

Extremely high nutrient lake.

Question 21

Liebig’s law of the minimum

Answer 21

Liebig’s law of the minimum states growth is controlled by the scarcest resource available - usually phosphorus.