Algal blooms impart a distinct colour to water due to

Options

A. Their pigments
B. Excretion of coloured substsces
C. Formation of coloured chemicals in water facilitated by physiological degradation of algae
D. Absorption of light by algal cell wall

Answer

### Step-by-Step Solution

1. **Understanding Algal Blooms**: Algal blooms are rapid increases in the population of algae in water bodies, often due to favorable environmental conditions such as nutrient enrichment, sunlight, and warm temperatures.

2. **Identifying the Cause of Color Change**: The distinct color imparted to water during algal blooms is primarily due to the presence of pigments in the algae. These pigments are responsible for photosynthesis and can absorb different wavelengths of light.

3. **Role of Chlorophyll**: The primary pigment in most algae is chlorophyll, which is essential for photosynthesis. Chlorophyll absorbs light primarily in the blue and red wavelengths, reflecting green light, which is why many algae appear green.

4. **Accessory Pigments**: In addition to chlorophyll, algae may contain accessory pigments such as carotenoids and phycobilins. These pigments allow algae to capture additional light wavelengths, contributing to the variety of colors observed in algal blooms (e.g., red tides, brown tides).

5. **Conclusion**: The distinct color of water during algal blooms is mainly due to the pigments present in the algae. Therefore, the correct answer to the question is that algal blooms impart a distinct color to water due to their pigments.

### Final Answer
**Algal blooms impart a distinct color to water due to their pigments.**

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