Question

Water bloom is generally caused by
A. Green algae
B. Blue-green algae
C. Bacteria
D. Hydrilla

Answer 1

Hint: Water bloom is caused by rapid increase in the population of algae causing the water body to change its colour. It is caused by a type of bacteria called cyanobacteria.

Complete Answer:
- Planktonic algae are microscopic algae living in the water. They often cause the water to appear green, brown or reddish in colour. Plankton algae grow very rapidly when conditions are ideal in the summer, often culminating in a bloom where the pond water becomes turbid or coloured within a day or two.
- Algae boom or water bloom is a sudden rise in the abundance of algae in the marine environment. The colours seen are green, yellowish-brown or red. Bright green blooms can also occur. They are the product of blue-green algae, which are actually bacteria (cyanobacteria).
- The more algae and plants grow other plants in the water die. This dead organic matter becomes a food for the bacteria that breaks it down. With more food present, the amount of bacteria increases and dissolved oxygen is used up in the water. As the dissolved oxygen content is decreased, many fish and aquatic insects cannot survive leading to death of aquatic animals.
- Hydrilla is an invasive aquatic plant species. Its ability to thrive under diverse environments gives it an advantage that helps it to out-compete native plants. Hydrilla infestations can also be detrimental to fish populations. Huge infestations can create oxygen deprivation areas, which can contribute to the death of fishes.

Thus, the correct answer is option B, Blue-green algae.

Note: While plankton algae bloom in response to warm and sunny summer weather, the growth of algae is enabled by high levels of nutrients in water (most frequently phosphorus and nitrogen) that can come from fertilisers, manures, urban drainage or animal waste entering the water bodies.