Trichodesmium erythraeum which gives colour to Red Sea is

Options

A. Green alga
B. Blue- green alga
C. Red alga
D. Brown alga.

Answer

To answer the question about Trichodesmium erythraeum, which gives color to the Red Sea, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Organism**: The organism in question is Trichodesmium erythraeum. It is a type of cyanobacteria.

2. **Understand the Role of Trichodesmium erythraeum**: This organism is known for its ability to bloom in certain conditions, which can lead to a significant change in the color of the water in the Red Sea.

3. **Color Contribution**: The red color of the Red Sea is attributed to the blooms of Trichodesmium erythraeum. These blooms can give the water a reddish hue.

4. **Classification**: Trichodesmium erythraeum is classified as a cyanobacterium. Cyanobacteria are often referred to as blue-green algae due to their color and photosynthetic pigments.

5. **Select the Correct Option**: Given the options (green alga, blue alga, blue-green alga, red alga, or brown alga), the correct classification for Trichodesmium erythraeum is "blue-green alga".

6. **Conclusion**: Therefore, the answer to the question is that Trichodesmium erythraeum, which gives color to the Red Sea, is a blue-green alga.

### Final Answer:
**Trichodesmium erythraeum is a blue-green alga.**

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