Physical and Chemical Processes in Lakes

Question 1

The Hutchinsonian niche is an n-dimensional hypervolume enclosing the complete range of conditions under which an organism can reproduce itself. What are the 5 main factors that affect an organisms niche?

Answer 1

• Temperature
• Light
• pH
• Nutrients (C, N, P)
• Oxygen

Question 2

What is thermosensitivity?

Answer 2

The range of temperatures an
organism can tolerate.
– Thermal specialists have a small temperature range.
– Thermal generalists have a large temperature range.

Question 3

What is thermoregulation?

Answer 3

The extent to which an organism’s temperature reflects that of its environment.
– Perfect thermoregulators maintain a constant temperature
despite environmental variation (homeotherms).
– Perfect thermoconformers exactly match the temperature
of the environment (poikilotherms).

Question 4

What is homeotherms and poikilotherms?

Answer 4

– Perfect thermoregulators maintain a constant temperature
despite environmental variation (homeotherms).
– Perfect thermoconformers exactly match the temperature
of the environment (poikilotherms).

Question 5

There are 5 types of thermal adaptations, name 3.

Answer 5

• Acclimatization
• Avoidance, e.g. through resting stages
• Behavioral thermoregulation
• Genetic adaptation
• Evolutionary constraints, e.g. warm and cold-
  water fishes

Question 6

What is a secchi desk used for?

Answer 6

To measure turbidity in the water (how deep is the photic zone?)

Question 7

What is the pH range of acidified, “normal” (most lakes), and alkaline lakes?

Answer 7

Acidified: 2-6
Most lakes: 6-9
Alkaline: 9-12

Question 8

What happens to the pH when photosynthesis consumes CO2?

Answer 8

The pH increases (day).

Question 9

What happens to the pH when photosynthesis releases CO2?

Answer 9

The pH decreases (night).

Question 10

What is the difference between photosynthesis and respiration?

Answer 10

Photosynthesis consumes CO 2 and releases O 2
Respiration consumes O 2 and releases CO 2

Question 11

What is net autotrophic?

Answer 11

photosynthesis > respiration
(positive NEP)

Question 12

What is net heterotrophic?

Answer 12

Respiration > photosynthesis
(negative NEP)

Question 13

What are the 3 factors that impact net ecosystem production (NEP)?

Answer 13

– Allochthonous carbon loading (DOC, POC)
– Phosphorus availability
– Food web structure

Question 14

They are 2 sources of carbon in a lake, what are they and what are they called?

Answer 14

Autochthonous – from within the lake (CO 2 )
Allochthonous – from outside the lake (DOC)

Question 15

Redfield ratio is the relative amount of carbon, nitrogen and phosphorous in planktonic organisms and the surrounding water. what is the ratio?

Answer 15

C:N:P - 106:16:1

Question 16

There are 2 types of ecosystem engineers, what are they?

Answer 16

• Allogenic engineers – modify the environment by changing materials from one form into another (e.g. beavers)
• Autogenic engineers – modify the environment by via their own structures (e.g. macrophytes).