There is a concern over the increase in harmful algal blooms in the seawaters of India. What could be the causative factors for this phenomenon?

1. Discharge of nutrients from the estuaries.
2. Run-off from the land during the monsoon.
3. Upwelling in the seas.

Select the correct answer from the codes given below:

[UPSC Civil Services Exam – 2011 Prelims]

(a) 1 and 3

(b) 1 and 2 only

(c) 2 and 3 only

(d) 1, 2 and 3

Answer: (d)        

Explanation:

Algal Bloom:

• An algal bloom is defined as the rapid growth of the population of algae in aquatic ecosystems.
• Algal blooms are caused by excessive amounts of nitrates, phosphates, and nutrients entering an aquatic ecosystem, often via discharges from sewage treatment plants and septic tanks, estuaries, and stormwater run-off from fertilized lawns and farms. Hence, statements 1 and 2 are correct.
• Other factors that responsible for algal growth include sunlight and slow-moving water.
• Upwelling, the formation of mud banks, nutrient discharges from estuaries, and run-off from the land during southwest and northeast monsoons cause some algae blooms in coastal waters. Hence, statement 3 is correct.