Question

Described below are the three steps in the process of how eutrophication leads to total destruction of aquatic life. Choose the option which has the correct sequence of these steps.
i) Algae die off, hence a large amount of organic matter is released.
ii) Bacteria begin to degrade organic matter, leading to a decrease in dissolved oxygen.
iii) Increase in nutrient concentrations causes a sudden growth spurt in algae.

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

The first step in eutrophication is an increase in nutrient concentrations in the water, which causes algal bloom. The algal bloom causes an increase in Biological Oxygen Demand. 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 hypoxic.