Increase in the population of decomposing bacteria in a water body kills the aquatic life because of:

Options

A. Lack of oxygen
B. Lack of carbon dioxide
C. Excess of oxygen
D. Excess of nitrogen

Answer

To solve the question regarding why an increase in the population of decomposing bacteria in a water body kills aquatic life, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Role of Decomposing Bacteria**:
- Decomposing bacteria are microorganisms that break down organic matter in water bodies. They play a crucial role in the ecosystem by recycling nutrients.

2. **Impact of Water Pollution**:
- Water pollution introduces excess nutrients (like nitrogen and phosphorus) into the water. These nutrients often come from sources such as agricultural runoff, sewage discharge, and industrial waste.

3. **Nutrient Enrichment and Bacterial Growth**:
- The excess nutrients in the water promote the rapid growth of decomposing bacteria. This phenomenon is known as eutrophication.

4. **Oxygen Consumption**:
- As the population of bacteria increases, they consume more oxygen in the process of decomposing organic matter. This is particularly significant because the amount of dissolved oxygen in water is limited.

5. **Consequences for Aquatic Life**:
- Aquatic organisms, such as fish and other marine life, rely on dissolved oxygen to survive. When the bacteria consume a large amount of oxygen, the levels of dissolved oxygen decrease significantly.

6. **Resulting Harm to Aquatic Life**:
- The decrease in dissolved oxygen leads to hypoxia (low oxygen levels) or anoxia (absence of oxygen), which can suffocate aquatic life, leading to their death.

7. **Conclusion**:
- Therefore, the increase in the population of decomposing bacteria in a water body kills aquatic life primarily due to the lack of oxygen.

### Final Answer:
The increase in the population of decomposing bacteria in a water body kills aquatic life because of the lack of oxygen.

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