Name the alga which is mainly responsible for the red tides in many sea coasts.

Explanation

**Step-by-Step Solution:**

1. **Understanding Red Tides**: Red tides refer to harmful algal blooms, which are rapid increases in the population of algae in water bodies. These blooms can have detrimental effects on marine life and human health.

2. **Identifying the Cause**: Various species of algae can cause red tides, particularly dinoflagellates and diatoms. These organisms thrive when conditions such as nutrient availability and favorable temperatures are optimal.

3. **Specific Alga Responsible**: Among the different types of algae, one specific genus is known for causing red tides. This genus is recognized for its ability to proliferate rapidly and produce toxins.

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