Ecology- Lake Stratiication

Question 1

When do lakes stratify?

Answer 1

During summer months from increased solar radiation, with weak summer wind unable to mix the dense cold water beneath.

Question 2

Why does spring and summer support algal blooms?

Answer 2

As deep-layer nutrients are brought up from the mixing period in the winter and early spring.

Question 3

Microbial Loop

Answer 3

Models aquatic ecosystems loop food web comprising bacteria, dinoflagellates, ciliates and other zooplankton.

Question 4

What sunlight do lakes recieve?

Answer 4

Shortwave solar and reflected longwave.

Question 5

How is stratfication ecologically important?

Answer 5

When stratified, the metalimnion prevents water-column mixing, thus isolating hypolimnion from atmospheric gas exchange

Question 6

When might the hypolimnion recieve light for photosynthesis?

Answer 6

Clearer lakes allow deeper penetration

Question 7

Types of lake based on stratification?

Answer 7

Dimictic
Monomictic
Oligomictic
Polymictic
Amictic
Meromictic

Question 8

Dimictic

Answer 8

Typical of temperate climates where stratification occurs twice a year.

Question 9

Monomictic

Answer 9

Experience turnover only once a year, thic can be cold or warm.

Question 10

Oligomictic

Answer 10

Do not stratify every year, found say in low humid and high wind equatorial regions, with little seasonal changes

Question 11

Polymictic

Answer 11

Stratify and mix throughout ice-free periods in lakes to shallow to thermally stratify.

Question 12

Amictic

Answer 12

Permanently stratified

Question 13

Meromictic

Answer 13

Contain eplimnion and metalimnion vertical mixing that does not extend to the hypolimnion.

Question 14

What happens to incident radiation on water?

Answer 14

Reflected, scattered or absropted.

Question 15

What does incidence light cause in water bodies?

Answer 15

Stratification

Question 16

Beer-lambert Law

Answer 16

This says that there is a linear relationship between concentration and absorbance of the solution.

Question 17

What can the beer-lambert law be used to measutre?

Answer 17

Vertical light attenuation of a water body, decreasing exponentially with depth.

Question 18

What IS wavelength absorption be determined by?

Answer 18

Dissolved substances and biota

Question 19

What is colour of water depednetn on?

Answer 19

Light scattering.

Question 20

Why does pure water appear blue?

Answer 20

Because blue wavelengths are scattered more-so

Question 21

When is water most dense?

Answer 21

4C

Question 22

What does difference in density increase with?

Answer 22

Increasing temperature, density difference between 24 and 25 is 30 times density difference between 4 and 5

Question 23

Epilimnion

Answer 23

This is the surface layer of a stratifed layer, typically warmer and with higher pH

Question 24

Metalimnion

Answer 24

This is the region where temperature gradient is rather steep

Question 25

Hyplimnion

Answer 25

This is the lowest, densest and coldest lyer of a water collumn

Question 26

When is wind-mixing least efficient?

Answer 26

When water temeprature is 4 degrees

Question 27

Why are deeper waters more stable?

Answer 27

Differences in density with low temperature differences are smaller than hot temperatures.

Question 28

Why does stratification occur?

Answer 28

Due to the proportionality of the temperature/decrease ratio

Question 29

When is stratification most stable?

Answer 29

Throughout summer

Question 30

Thermal Convection

Answer 30

Water mixing by temperature gradients.

Question 31

Trophogenic Zone

Answer 31

This is the layer photosynthesis occurs

Question 32

Tropholytic Zone

Answer 32

This is where dissimilation of OM predominatens, being the deeper layers

Question 33

Holomictic Lakes

Answer 33

These have low uniform temperature and density from surface to bottom at a specific time during the year