Eutrophication leads to death of fish due to

Options

A. Decreased O
2
​
concentration
B. Increased O
2
​
concentration
C. Both
D. None

Answer

### Step-by-Step Solution:

1. **Understanding Eutrophication**: Eutrophication is a process where water bodies become overly enriched with nutrients, particularly phosphorus and nitrogen. This can occur due to runoff from fertilizers, sewage discharge, and other sources.

2. **Effects of Eutrophication**: The excessive nutrients lead to rapid growth of algae and aquatic plants, a phenomenon known as algal blooms. These blooms can cover the surface of the water, blocking sunlight from reaching other aquatic plants.

3. **Decomposition Process**: When the algae die, they are decomposed by bacteria. This decomposition process requires oxygen, leading to a significant consumption of dissolved oxygen in the water.

4. **Oxygen Depletion**: As the bacteria break down the dead algae, they consume large amounts of oxygen in the water. This results in decreased oxygen concentration, which is critical for the survival of fish and other aquatic organisms.

5. **Consequences for Fish**: The reduction in oxygen levels can lead to hypoxia (low oxygen conditions) or anoxia (absence of oxygen), which can cause fish and other aquatic life to suffocate and die.

6. **Conclusion**: Therefore, eutrophication leads to the death of fish primarily due to decreased oxygen concentration in the water.

### Final Answer:
Eutrophication leads to the death of fish due to decreased oxygen concentration.

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