Which of the following sequences is correct in a hydrarch succession ?

Options

A. Zooplankton , free - floating plants , reed swamp , scrub , forest
B. Phytoplankton , rooted submerged plants , free - floating plants , marsh meadow, scrub, forest
C. Phytoplankton , free - floating plants , marsh meadow , reed swamp , scrub, forest
D. Phytoplankton , free - floating plants , rooted submerged plants, reed swamp , scrub, forest .

Answer

To solve the question regarding the correct sequence in a hydrach succession, we will analyze the options provided and understand the typical stages of hydrach succession.

### Step-by-Step Solution:

1. **Understanding Hydrach Succession**:
- Hydrach succession is a type of ecological succession that occurs in aquatic environments, particularly in wetlands. It begins with the colonization of pioneer species in water bodies and progresses towards the establishment of a climax community.

2. **Identifying Pioneer Communities**:
- The first stage of hydrach succession typically involves the establishment of pioneer communities, which are often composed of phytoplankton and other simple aquatic organisms.

3. **Analyzing the Options**:
- **Option 1**: Zooplankton, Free Floating Plant, Ridge Swamp, Shrub, and Forest.
- This sequence is incorrect because it does not start with phytoplankton, which are essential in the early stages.

- **Option 2**: Phytoplankton, Root Submerged Plant, Free Floating Plant, Marsh Medium, Shrub, and Forest.
- This sequence is correct as it follows the logical progression of hydrach succession, starting with phytoplankton, then moving to rooted submerged plants, followed by free-floating plants, marshes, shrubs, and finally forests.

- **Option 3**: Phytoplankton, Free Floating Plants, Marsh Medium, Reed Swamp, Shrub, and Forest.
- This sequence is incorrect because it places free-floating plants before rooted submerged plants.

- **Option 4**: Phytoplankton, Free Floating Plants, Rooted Submerged Plants, Reed Swamp, Shrub, and Forest.
- This sequence is also incorrect for the same reason as option 3; it does not follow the correct order of development.

4. **Conclusion**:
- After analyzing all options, the correct sequence in a hydrach succession is given in **Option 2**: Phytoplankton, Root Submerged Plant, Free Floating Plant, Marsh Medium, Shrub, and Forest.

### Final Answer:
The correct sequence in a hydrach succession is **Option 2**: Phytoplankton, Root Submerged Plant, Free Floating Plant, Marsh Medium, Shrub, and Forest.