Phytoplanktons in the hydrosere constitute

Options

A. Members of climax community
B. Pioneer community
C. First seral members
D. All of the above

Explanation

To solve the question regarding the role of phytoplanktons in the hydrosere, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Hydrosere**:
- The hydrosere refers to a type of ecological succession that occurs in aquatic environments. It starts in water bodies and progresses towards drier conditions.

**Hint**: Remember that hydrosere is a type of ecological succession specifically in wet areas.

2. **Identifying Phytoplanktons**:
- Phytoplanktons are microscopic plants that float in water. They are the first organisms to colonize aquatic environments in the early stages of succession.

**Hint**: Think of phytoplanktons as the "pioneers" of aquatic ecosystems.

3. **Role of Phytoplanktons in Succession**:
- In the hydrosere, phytoplanktons serve as the pioneer community. They are the first organisms to establish themselves in the newly formed or disturbed aquatic environment.

**Hint**: Pioneer species are crucial for starting the process of ecological succession.

4. **Progression of Succession**:
- As succession progresses, phytoplanktons are gradually replaced by other plant communities, such as submerged plants, floating plants, and eventually larger vegetation, leading to a climax community.

**Hint**: Climax communities are typically characterized by larger, more complex plants, not by phytoplanktons.

5. **Conclusion**:
- Based on the role of phytoplanktons in the hydrosere, they are classified as members of the pioneer community, not the climax community.

**Hint**: Focus on the definitions of pioneer and climax communities to clarify their roles in succession.

### Final Answer:
Phytoplanktons in the hydrosere constitute members of the **pioneer community**.