A water body characterized by nutrient rich water supports abundant growth of phytoplankton and other water plants on its surface. Over time, the water body gets filled with a large number of such plants and the process is called Eutrophication. In such water bodies, dissolved oxygen content is nil or very less.
Eutrophicated water usually looks turbid green in colour because of ________

Options

A. excessive growth of phytoplankton
B. accumulation of minerals and nutrients
C. water body becoming polluted
D. release of degraded plant chlorophyll in water

Answer

**Step-by-Step Solution:**

1. **Understanding Eutrophication**: Eutrophication is a process that occurs in water bodies where there is an excessive growth of aquatic plants and phytoplankton due to high nutrient levels, particularly nitrogen and phosphorus. This often results from human activities such as agricultural runoff and wastewater discharge.

**Hint**: Think about what causes the nutrient levels in water bodies to increase.

2. **Effects of Eutrophication**: As the nutrient levels rise, phytoplankton and algae grow rapidly, leading to a dense layer of plant life on the water's surface. This growth can block sunlight from reaching other aquatic plants and disrupt the ecosystem.

**Hint**: Consider how the growth of these organisms affects the light penetration in the water.

3. **Dissolved Oxygen Levels**: The dense growth of phytoplankton and algae can lead to a decrease in dissolved oxygen levels in the water. When these organisms die, their decomposition consumes oxygen, leading to hypoxic (low oxygen) conditions.

**Hint**: Reflect on the relationship between plant growth and oxygen levels in water.

4. **Color of Eutrophicated Water**: Eutrophicated water appears turbid green primarily due to the excessive growth of phytoplankton and algae. These organisms contain chlorophyll, which gives them a green color. The high concentration of these organisms in the water makes it look green and murky.

**Hint**: Focus on the visual characteristics of the organisms that thrive in nutrient-rich waters.

5. **Conclusion**: Therefore, the eutrophicated water looks turbid green in color because of the excessive growth of phytoplankton.

**Final Answer**: Eutrophicated water usually looks turbid green in color because of **excessive growth of phytoplankton** (Option A).

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