A water body characterized by nutrient rich water supports abundant growth of phytoplankton and other water plants on its surface. Over time, the water body gets filled with a large number of such plants and the process is called Eutrophication. In such water bodies, dissolved oxygen content is nil or very less.
Which of the following statement is correct?

Options

A. In eutrophic water bodies, dissolved oxygen content is more.
B. Eutrophication does not have any effect on the dissolved oxygen in the water body.
C. In eutrophic water bodies, dissolved oxygen content is nil or very less.
D. We should encourage eutrophication for improving dissolved oxygen in a water body.

Answer

To solve the question regarding eutrophication and its effects on dissolved oxygen levels in water bodies, we will analyze the statements provided and determine which one is correct.

### Step-by-Step Solution:

1. **Understanding Eutrophication**:
- Eutrophication is a process that occurs in water bodies when there is an excess of nutrients, particularly nitrogen and phosphorus. This leads to the rapid growth of phytoplankton and aquatic plants.

**Hint**: Remember that eutrophication is linked to nutrient enrichment.

2. **Effects of Eutrophication**:
- As phytoplankton and aquatic plants grow abundantly, they eventually die and decompose. This decomposition process consumes a significant amount of dissolved oxygen in the water.

**Hint**: Consider the life cycle of phytoplankton and the consequences of their death.

3. **Analyzing the Statements**:
- **Statement 1**: "In eutrophic water bodies, dissolved oxygen content is more."
- This is incorrect because eutrophication leads to a decrease in dissolved oxygen levels.

- **Statement 2**: "Eutrophication does not have any effect on the dissolved oxygen in the water body."
- This is also incorrect as eutrophication significantly reduces dissolved oxygen levels due to decomposition.

- **Statement 3**: "In eutrophic water bodies, the dissolved oxygen content is nil or very less."
- This statement is correct as it aligns with the understanding that eutrophication leads to low or nil dissolved oxygen levels.

- **Statement 4**: "We should encourage eutrophication for improving dissolved oxygen in the water body."
- This statement is incorrect because encouraging eutrophication would further decrease dissolved oxygen levels.

4. **Conclusion**:
- The correct statement is: "In eutrophic water bodies, the dissolved oxygen content is nil or very less."

### Final Answer:
The correct statement is: **"In eutrophic water bodies, the dissolved oxygen content is nil or very less."**