What is eutrophication?

Explanation

### Step-by-Step Solution:

1. **Definition of Eutrophication**: Eutrophication is a natural process that occurs in aquatic ecosystems, characterized by the gradual increase in nutrient concentrations, particularly phosphorus and nitrogen.

2. **Nutrient Increase**: The process begins when there is an increase in the concentration of essential nutrients in the water. These nutrients are vital for plant growth and can come from various sources, including agricultural runoff, sewage discharge, and industrial waste.

3. **Microorganism Growth**: As the nutrient levels rise, they promote the rapid growth of microorganisms, especially blue-green algae (cyanobacteria). This phenomenon is often referred to as algal bloom.

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