Question

Which of the following statements is not correct regarding algal blooms ?

• A. Algal blooms are formed by blue-green algae
• B. Growth of Eichhornia crassipes causes colouration of water during algal blooms
• C. Increased growth of algae causes depletion of $O_2$ in water
• D. Algal blooms cause deterioration of water quality and fish mortality

Answer 1

The correct option is B Growth of Eichhornia crassipes causes colouration of water during algal blooms

An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems and is recognized by the discolouration in the water from their pigments.

A. Typically only one or a few phytoplankton species of algae are involved and some blooms may be recognized by discolouration of the water resulting from the high density of pigmented cells. Bright green blooms may also occur.

due to blue-green algae. So, this option is correct.

B. Eichhornia crassipes, commonly known as common water hyacinth, is an aquatic plant. It is not an alga. So, this option is not correct.

C. As more algae and plants grow, others die. This dead organic matter becomes food for bacteria that decompose it. With more food available, the bacteria increase in number and use up the dissolved oxygen in the water. So depletion of the oxygen causes. So, this option is correct.

D. When the dissolved oxygen content decreases, many fish and aquatic insects cannot survive. This results in a dead area. So, this option is correct.

So the answer is 'Growth of Eichhornia crassipes causes colouration of water during algal blooms'.