Correct Answer - Option 3 : Acidic
Explanation:
- Most of the algae are aquatic and are found in freshwater or marine habitats.
- Therefore, they are related to different aspects of fresh-water or marine pollution.
Algae as pollution indicators:
The growth pattern of the algal flora in a water body can be used to identify the type and level of water pollution.
1. Water acidity:
- An increase in the acidity of water initially causes a general increase in algae.
- However, high levels of water acidity due to pollution by acid-forming chemicals or acid rains result in a decrease in planktonic algae in the water body.
2. Sewage, organic matter, and chemical fertilizers:
- An increase in the organic matter or chemical fertilizers that are washed off into the water body results in increased nutrient supply for algal growth.
- Such a condition of increased nutrient supply is termed eutrophication and results in water blooms of various types of algae.
4. Heavy metals:
- Some algae absorb and accumulate many heavy metals from the water.
- Thus the excessive growth of these algae in the water indicates pollution due to heavy metals.
