Question

The green scum seen in the freshwater bodies are
A. Blue-green algae
B. Red algae
C. Green algae
D. Both A and C

Answer 1

Hint: The green scums in freshwater bodies are referred to as algal blooms. Algal blooms are observed in different colors like green, red, brown depending on the color of the organism causing them.

Complete answer:
Option A: Blue-green algae are a type of bacteria known as cyanobacteria. They are photosynthetic in nature. When the level of nutrients such as phosphorus and nitrogen in the water is high, it favors the exponential growth of blue-green algae. This appears as a green color scum in water bodies. These algal blooms reduce the quality of water by using up the oxygen in the water and thereby reducing oxygen content in water. This affects the lives of other aquatic organisms. In severe cases, this could lead to the death of the lake. Green algae also contribute to the green algal bloom. Therefore, this is the incorrect option.

Option B: Red algae are also known as Rhodophyta. They are mostly freshwater, but also found in marine water. Red algae, as the name implies, are red in color. This is because of the pigments chlorophyll A, phycocyanin, and phycoerythrin present in them. Their clustered growth in water bodies will appear red in color. Therefore, this is the incorrect option.

Option C: Green algae are photosynthetic algae with pigments chlorophyll a and b along with auxiliary pigments xanthophylls and beta carotenoids. Hey, can also cause green color scum in freshwater. They are not the only ones causing green scum. Therefore, this is the incorrect option.

Option D: Since both blue-green algae and green algae contribute to the green color algal blooms in freshwater bodies, this is the correct option.

Hence, the correct answer is option (D)

Note: Algal blooms are mainly produced by cyanobacteria, but all other algae also contribute to this.
Photosynthetic algae use up the oxygen content in water. The decay of these algae, once they are dead, will also consume oxygen. This eventual death of a waterbody ecosystem is called eutrophication.