Question

Frequent occurrence of water blooms in a lake indicates

• A. Nutrient deficiency
• B. Oxygen deficiency
• C. Excessive nutrient pollution
• D. Absence of herbivores in the lake

Answer 1

Answer: (C)

Excessive nutrient pollution

Organic loading is the occurrence of excess organic matter inside water due to sewage disposal and eutrophication. This leads to an increase in biological oxygen demand (BOD) for putrefaction by microorganisms. Also, explosive multiplication of blue-green alga leads to an algal bloom. These conditions result in a decrease in dissolved oxygen in the water. Both toxicity due to algal toxins and decreased levels of dissolved oxygen kill aquatic animals.