Question

Described below are the three steps in the process of how eutrophication leads to total destruction of aquatic life.

i) Algae grow rapidly and eventually die off.
ii) Decrease in dissolved oxygen in water body.
iii) Increase in nutrient concentrations .

Choose the option which has the correct sequence of these steps.

• A. $i\to iii\to ii$
• B. $ii\to i\to iii$
• C. $iii\to i\to ii$
• D. $i\to ii\to iii$

Answer 1

The correct option is C $iii\to i\to ii$

Eutrophication or death of water body starts with the increase in nutrient concentrations in the water body followed by a sudden growth spurt in algae. The algal bloom causes an increase in craving for oxygen. Soon the algae start to die and leave behind a lot of organic matter. The bacteria then begin working on the organic matter. This decomposition demands huge amounts of oxygen, which further reduces the dissolved oxygen levels in the water, making it dead.