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.

Choose the correct answer from the codes given below:

The correct answer is 1, 2 and 3.

Key Points

• Algal Bloom:
  • An algal bloom is defined as the rapid growth of the population of algae in aquatic ecosystems. 
  • Algal blooms can be found in either a marine environment or a freshwater environment.
  • The phenomenon can be easily recognised by the discolouration on the surface of the water. It usually occurs due to the introduction of a nutrient (such as nitrogen or phosphorus) into an aquatic ecosystem.
  • Algae is a term that is used to describe both unicellular and multicellular, photosynthetic organisms. Discolouration of the water characterises a unicellular algal bloom. Giant kelp forests are examples of a multicellular algal bloom.
  • 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.