Gonyaulax is a protist which

Options

A. causes an algal bloom where its rapid multiplication changes the sea colour
B. leads to the formation of diatomaceous earth
C. behaves like a heterotroph in the absence of sunlight
D. has an infectious spore - like stage in their life cycle and has a staggering effect on the human population .

Answer

To solve the question regarding Gonyaulax, we need to analyze each option provided in the context of what we know about this protist.

### Step-by-Step Solution:

1. **Identify Gonyaulax**:
Gonyaulax is classified under the Kingdom Protista and specifically belongs to the group known as dinoflagellates.

**Hint**: Remember that dinoflagellates are a type of protist that are primarily marine and photosynthetic.

2. **Understanding Algal Blooms**:
Algal blooms occur when there is a rapid increase in the population of algae in water bodies. Gonyaulax can cause such blooms, particularly red tides, which are characterized by the red coloration of the water due to the high concentration of these organisms.

**Hint**: Think about how certain algae can multiply quickly and affect the color of water.

3. **Evaluating Each Option**:
- **Option a**: "Causes an algal bloom where its rapid multiplication changes the sea color."
- This is true as Gonyaulax can cause red tides, changing the color of the sea.

- **Option b**: "Leads to the formation of diatomaceous earth."
- This is incorrect. Diatomaceous earth is formed from diatoms, not dinoflagellates like Gonyaulax.

- **Option c**: "Behaves like heterotroph in the absence of sunlight."
- While some dinoflagellates can exhibit heterotrophic behavior, Gonyaulax is primarily photosynthetic and does not typically behave like a heterotroph in the absence of sunlight.

- **Option d**: "Has an infectious pole-like stage in their life cycle and a staggering effect on a human population."
- This is misleading. Gonyaulax does produce toxins that can affect marine life and humans, but it does not have a pole-like infectious stage.

4. **Conclusion**:
The correct answer is **Option a**: "Causes an algal bloom where its rapid multiplication changes the sea color."

### Final Answer:
**Option a**: Causes an algal bloom where its rapid multiplication changes the sea color.