Question

Identify the correct statements regarding the thermal stratification layers in a lake during summer.

1. The epilimnion is the upper layer, characterized by warm, circulating water, rich in nutrients, and supporting phytoplankton growth.
2. The metalimnion is the intermediate layer where water temperature decreases sharply with increasing depth.
3. The hypolimnion is the bottom layer, which is cold, non-circulating, and typically low in oxygen but rich in nutrients.
4. Phytoplankton predominantly grow in the hypolimnion due to high nutrient availability.

• A. 2 only
• B. 3 only
• C. 2, 3
• D. 1, 3

Answer 1

Answer:

C. 2, 3

Metalimnion

• This zone lies below the epilimnion and above the hypolimnion and thus forms the intermediate layer which is non-circulating.

• The metalimnion is characterised by steep and rapid fall in water temperature with increasing depth.

Hypolimnion

This zone forms the bottom layer which is deep, cold and non circulating.

The hypolimnion is generally rich in nutrients though its oxygen content is low due to its utilisation by decomposition process which as you know generally occurs here and uses up oxygen.

Temperature fall here is gentle.