In which of the zone of lake stratification only heterotrophs are present?
(a) Limnetic zone
(b) Littoral zone
(c) Profundal zone
(d) Ecotone zone

Options

A. Limnetic zone
B. Littoral zone
C. Profundal zone
D. Ecotone zone.

Answer

To determine which zone of lake stratification contains only heterotrophs, we need to analyze the characteristics of each zone mentioned in the options.

### Step-by-step Solution:

1. **Understand Lake Stratification:**
- Lakes are stratified into different zones based on depth, light penetration, and biological communities. The main zones include the littoral zone, limnetic zone, profundal zone, and benthic zone.

2. **Identify the Zones:**
- **Littoral Zone:** This is the shallow area near the shore where sunlight penetrates to the bottom. It supports a variety of plants and organisms, including autotrophs (like aquatic plants) and heterotrophs (like fish and invertebrates).
- **Limnetic Zone:** This is the open water area that is well-lit and supports plankton and fish. It is primarily populated by autotrophs (like phytoplankton) and heterotrophs (like zooplankton and fish).
- **Profundal Zone:** This is the deep water zone where light does not penetrate. It is below the limnetic zone and above the benthic zone. This zone is primarily inhabited by heterotrophs, as there is no light for photosynthesis.
- **Benthic Zone:** This is the bottom layer of the lake, where decomposers and detritivores (heterotrophs) are found, but it is not exclusively heterotrophic.

3. **Analyze the Options:**
- (a) Limnetic zone: Contains both autotrophs and heterotrophs.
- (b) Littoral zone: Contains both autotrophs and heterotrophs.
- (c) Profundal zone: Primarily inhabited by heterotrophs, as it lacks light for photosynthesis.
- (d) Ecotone zone: This is a transitional area and not a specific zone of lake stratification.

4. **Conclusion:**
- The zone of lake stratification that contains only heterotrophs is the **Profundal Zone**. Therefore, the correct answer is **(c) Profundal zone**.