Natural ageing of lake by biological enrichment of its water is called

Options

A. Biomagnification
B. Eutrophication
C. Biodegradation
D. Water logging

Answer

**Step-by-Step Solution:**

1. **Understanding Biological Enrichment**: Biological enrichment refers to the process where water bodies, such as lakes, become enriched with nutrients and minerals. This can occur naturally over time as organic matter decomposes and releases nutrients into the water.

2. **Identifying the Process**: The natural aging of a lake due to biological enrichment is a gradual process. As nutrients accumulate, they can lead to increased biological activity, particularly the growth of algae and other aquatic plants.

3. **Defining Eutrophication**: The specific term for the natural aging of a lake through biological enrichment is called "eutrophication." Eutrophication occurs when excessive nutrients, particularly phosphorus and nitrogen, lead to an overgrowth of algae (algal blooms).

4. **Consequences of Eutrophication**: As algae grow rapidly, they can block sunlight from reaching deeper water, which can harm other aquatic organisms. The decay of this algal bloom can deplete oxygen levels in the water, leading to dead zones where aquatic life cannot survive.

5. **Eliminating Incorrect Options**:
- **Biomagnification**: This refers to the accumulation of toxic substances in organisms as they move up the food chain, which is not related to the natural aging of lakes.
- **Biodegradation**: This is the breakdown of organic material by microorganisms, which does not pertain to the aging of a lake.
- **Water Logging**: This refers to the saturation of soil with water, affecting plant growth, and is unrelated to lake aging.

6. **Conclusion**: The correct answer to the question is "eutrophication," as it describes the natural aging of a lake through biological enrichment of its water.

**Final Answer**: Eutrophication

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