Question

Which of the following statements are correct in relation to winter stratification?

• A. Only (i) and (iv) are correct
• B. Only (i) and (iii) are correct
• C. Only (ii) and (iv) are correct
• D. Only (i) and (ii) are correct

Hint:

During winter stratification, ice forms at 0°C at the surface, while dense 4°C water sinks below; aquatic life survives under the ice layer.

Answer 1

The Correct Option is D

Step 1: Understand winter stratification.
- Winter stratification occurs in lakes and ponds due to temperature gradients in water.
- Water has maximum density at 4°C, which affects layering.

Step 2: Analyze statement (i).
- The upper water freezes at 0°C in winter - Correct
- Ice forms at the surface because water below 4°C is denser and sinks, leaving the surface to freeze.

Step 3: Analyze statement (ii).
- Below the icy layer, water at 4°C sinks to the bottom - Correct
- This is the densest water, providing insulation and oxygenated habitat for aquatic life.

Step 4: Analyze statement (iii).
- Oxygen consumption rate increases at lower temperatures - Incorrect
- Metabolic rates of aquatic organisms decrease in cold water, so oxygen consumption decreases.

Step 5: Analyze statement (iv).
- Organisms cannot survive below frozen upper water - Incorrect
- Aquatic life survives in 4°C water below ice due to insulation and oxygen supply.

Step 6: Conclusion.
- Correct statements are only (i) and (ii).