Question

During thermal stratification, eutrophication starts

• A. At the end of thermal stratification
• B. At the start of thermal stratification
• C. In the upper layers during stratification
• D. In the lower layers during stratification

Answer 1

Answer: (C)

In the upper layers during stratification

Lake stratification is the separation of lakes into three layers. The thermal stratification of lakes refers to a change in the temperature in the lake at different depths. It is due to the change in density of water with change in temperature. Cold water is denser than warm water and the upper layer consists of water that is not as dense as the water in the lower layer. However, the temperature of maximum density for freshwater is $4^0$ C. Eutrophication starts from the upper layers during stratification.

Thus, the correct answer is option C.