The Algal bloom

Options

A. Is caused due to a large amount of nutrients in water
B. Imparts distinct colour to the water bodies
C. Causes fish mortality and deterioration of water quality
D. All of these

Answer

### Step-by-Step Solution:

1. **Understanding Algal Bloom**: Algal bloom refers to the rapid increase or accumulation of algae in water bodies, which can occur in both freshwater and marine environments. This phenomenon is often characterized by a distinct color change in the water due to the pigments produced by the algae.

2. **Causes of Algal Bloom**: The primary cause of algal bloom is eutrophication, which is the process of nutrient enrichment in water bodies. This is typically due to high levels of nutrients, particularly phosphorus and nitrogen, which can come from agricultural runoff, sewage discharge, and other sources.

3. **Effects on Water Quality**: As algae proliferate, they can significantly deteriorate the quality of water. The increase in organic content leads to higher Biochemical Oxygen Demand (BOD), which is the amount of oxygen required by bacteria and fungi to decompose organic matter.

4. **Impact on Aquatic Life**: The rise in BOD indicates that more oxygen is being consumed in the decomposition process, which results in lower levels of dissolved oxygen in the water. This can lead to fish mortality, as aquatic organisms struggle to survive in oxygen-depleted conditions.

5. **Conclusion**: Therefore, algal bloom is caused by nutrient enrichment leading to distinct color changes in water bodies, increased fish mortality, and overall deterioration of water quality. The correct answer to the question is "all of these."