Red sea is named after the abundant occurrence of

Options

A. Red coloured planktonic cyanobacterium Trichodesmium erythraeum
B. Red coloured hypnospores of Chlamy- domonas nivalis
C. Dinoflagella Gonyaulax species
D. Red alga Rhodymenia.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks why the Red Sea is named so, specifically what is abundant in the sea that leads to its name.

2. **Identifying the Options**: We have four options to consider:
- A) Red-coloured plant-tonic cyanobacterium *Trichodesmium erythrium*
- B) Red-coloured hypnospores of *Clemydomonus nivellus*
- C) *Dinofragila goni olex* species
- D) Red algae *Rhodomania*

3. **Analyzing the Red Sea**: The Red Sea is located between the East African coast and the Saudi Arabian peninsula. It is known for being one of the saltiest seas and does not have any rivers flowing into it.

4. **Researching the Color**: The name "Red Sea" is derived from the presence of certain microorganisms that can give the water a reddish hue. The primary organism responsible for this color is a type of cyanobacterium.

5. **Identifying the Correct Organism**: Among the options, the organism that is known to cause the reddish color in the Red Sea is the red-coloured plant-tonic cyanobacterium *Trichodesmium erythrium*.

6. **Evaluating Other Options**: The other options do not have a significant presence in the Red Sea or do not contribute to its name:
- B) *Clemydomonus nivellus* is not known for a significant presence in the Red Sea.
- C) *Dinofragila goni olex* species is not relevant.
- D) *Rhodomania*, while it is a type of algae, does not account for the name of the Red Sea.

7. **Conclusion**: The correct answer is option A: the Red Sea is named after the abundant occurrence of the red-coloured plant-tonic cyanobacterium *Trichodesmium erythrium*.

**Final Answer**: The Red Sea is named after the abundant occurrence of red-coloured plant-tonic cyanobacterium *Trichodesmium erythrium* (Option A).

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