What would happen if phytoplankton of an ocean is completely destroyed for some reason?

1. The ocean as a carbon sink would be adversely affected.
2. The food chains in the ocean would be adversely affected.
3. The density of ocean water would drastically decrease.

Select the correct answer using the codes given below:

[UPSC Civil Services Exam – 2012 Prelims]

(a) 1 and 2 only

(b) 2 only

(c) 3 only

(d) 1, 2 and 3

Answer: (a)        

Explanation:

Phytoplankton:

• Phytoplankton is mostly microscopic, single-celled photosynthetic organisms that live suspended in water.
• Like land plants, they take up carbon dioxide, make carbohydrates using light energy, and release oxygen.
• They are what is known as primary producers of the ocean—the organisms that form the base of the food chain.
• Phytoplankton also forms the base of virtually every ocean food web. Hence, statement 2 is correct.
• Because they take up carbon dioxide from the atmosphere, when they die they sink they carry this atmospheric carbon to the deep sea, making phytoplankton an important actor in the climate system. Hence, statement 1 is correct.
• If the phytoplankton of an ocean is completely destroyed for some reason, the density of ocean water would drastically decrease is an extreme statement. Thus, statement 3 is not correct.