Fertilisers added to fresh water will cause

Options

A. Death of plants
B. Decreases in fish popultation
C. Increases in aquatic animals
D. Eutrophication.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the effects of fertilizers when added to freshwater bodies. It is important to analyze how fertilizers interact with aquatic ecosystems.

2. **Identifying the Components of Fertilizers**: Fertilizers typically contain high levels of nutrients, particularly nitrogen and phosphorus. These nutrients are essential for plant growth but can have detrimental effects when they enter freshwater systems.

3. **Exploring the Process of Eutrophication**: When fertilizers enter freshwater bodies, they can lead to a process known as eutrophication. This occurs when excess nutrients stimulate the growth of algae and aquatic plants.

4. **Consequences of Eutrophication**: As algae bloom, they can block sunlight from reaching underwater plants, leading to their decline. When the algae die, their decomposition consumes oxygen in the water, resulting in hypoxic (low oxygen) conditions.

5. **Impact on Aquatic Life**: The decrease in oxygen levels can lead to the death of fish and other aquatic organisms, significantly reducing biodiversity and altering the ecosystem.

6. **Conclusion**: Therefore, the addition of fertilizers to freshwater bodies primarily causes eutrophication, which has cascading effects on the aquatic ecosystem, including the death of plants and a decrease in fish populations.

**Final Answer**: Fertilizers added to freshwater will cause eutrophication.

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