Question

The excessive increase in the number of aquatic plants creates a disturbance for the aquatic animals because

• A. It decreases dissolved oxygen content.
• B. It increases dissolved oxygen content.
• C. It increases dissolved carbon dioxide content.
• D. All of the above

Answer 1

The correct option is A It decreases dissolved oxygen content.

• In aquatic environments, free-floating microscopic plants known as algae, and larger submersed plants (macrophytes), release oxygen directly into the water where it is used by animals and other organisms, including the plants themselves.
• Fish and other aquatic organisms don’t use oxygen from water molecules ($H_{2}O$). This is because the single oxygen molecule ($O$) is bound to the two hydrogen molecules ($H_2$) and is not useable in this form.
• Instead, aquatic organisms depend on dissolved oxygen gas ($O_2$), a colourless, tasteless and odourless substance that enters the water from plants and the atmosphere. Hence, The excessive increase in the number of aquatic plants creates a disturbance for the aquatic animals because It decreases dissolved oxygen content.

So, the correct answer is 'It decreases dissolved oxygen content.'.