The green scum seen in the freshwater bodies is:
The green scum seen in the freshwater bodies is:

a. blue-green algae

b. red algae

c. green algae

d. both (a) and (c)

Answer: d. both (a) and (c)

Explanation: Green scum seen on the water body includes green algae as well as blue green algae. Excessive growth of algae is mainly due to the presence of phosphates or nitrates in the body of water (eutrophication). Such algal blooms can compress the body of water. Green algae and algae blue and green algae (cyanobacteria) are both photosynthetic and reduce the oxygen content dissolved in the body of water which kills many plants and animals of that aquatic body. Later, when microorganisms decompose these algae, further degradation of dissolved oxygen occurs.