Algal blooms are

Options

A. phytoplanktons
B. zooplanktons
C. rooted vegetation
D. submerged vegetation

Answer

### Step-by-Step Solution:

1. **Definition of Algal Bloom**: Algal blooms refer to the rapid increase or accumulation of algae in water bodies, often resulting in a greenish appearance on the surface of the water.

2. **Causes of Algal Blooms**:
- Algal blooms are primarily caused by the accumulation of nutrients in water bodies, particularly nitrogen and phosphorus.
- These nutrients often come from agricultural runoff, which includes fertilizers and pesticides that are washed into lakes and ponds.

3. **Natural Aging of Water Bodies**:
- Water bodies like lakes and ponds undergo a process known as natural aging or eutrophication.
- As nutrients accumulate, they promote the growth of algae and other organisms, leading to an increase in algal populations.

4. **Types of Algae**:
- The most common type of algae that proliferates during algal blooms is phytoplankton, which are microscopic, photosynthetic organisms that float in water.

5. **Visual Appearance**:
- Algal blooms can often be identified by their distinct green color on the surface of the water, which is a result of the dense concentration of phytoplankton.

6. **Impact of Algal Blooms**:
- While algal blooms can be a natural phenomenon, excessive blooms can lead to negative environmental impacts, such as depleting oxygen levels in the water and harming aquatic life.

### Final Answer:
Algal blooms are the rapid growth of phytoplankton in water bodies, often caused by nutrient accumulation from agricultural runoff, leading to a green appearance on the water's surface.

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