Question

Assertion (A): Eutrophication is harmful to the aquatic organisms.

Reason (R): Eutrophication is caused by the runoff of fertilisers from the fields into the water bodies.

Options

• Both A and R are true, and R is the correct reason for A.

• Both A and R are true, but R is not the correct reason for А.

• A is true, and R is false.

• A is false, and R is true.

Answer 1

Both A and R are true, and R is the correct reason for A.

Explanation:

Excess nutrient runoff (mainly nitrates and phosphates from fertilisers) stimulates excessive algal and phytoplankton growth (algal blooms). When that biomass decomposes, it consumes dissolved oxygen, causing oxygen depletion that is harmful and often lethal to fish and other aquatic organisms, so eutrophication (caused by fertiliser runoff) directly leads to harm.