Which of the following have coral reefs?

1. Andaman and Nicobar Islands
2. Gulf of Kachchh
3. Gulf of Mannar
4. Sunderbans

Select the correct answer using the code given below.

1. 1, 2 and 3 only
2. 2 and 4 only
3. 1 and 3 only
4. 1, 2, 3 and 4

Explanation

Option (a) is correct

• Coral reefs are found in the Andaman and Nicobar Islands, the Gulf of Kachchh, and the Gulf of Mannar.
• Ideal Conditions for Coral Growth:
  • Stable climatic conditions: Corals are highly susceptible to quick changes. They grow in regions where the climate is significantly stable for an extended period (equatorial oceans with warm ocean currents).
  • Perpetually warm waters: Corals thrive in tropical waters (30°N to 30°S latitudes; temperature around 20°C) where diurnal and annual temperature ranges are very narrow. (Coral reefs are absent on the west coast of tropical continents because of Cold Ocean Currents.)
  • Shallow water: Corals require a relatively good amount of sunlight to survive. The ideal depths for coral growth are 45 m to 55 m below the sea surface, where enough sunlight is available.
  • Clear salt water: Clear salt water is suitable for growth, while freshwater and highly saline water are harmful.
  • Abundant Plankton: An adequate supply of oxygen and microscopic marine food (plankton) is essential for growth. As the plankton is more abundant on the seaward side, corals proliferate on the seaward side.
  • Little or no pollution: Corals are highly fragile and are vulnerable to climate change and pollution, and even a minute increase in marine pollution can be catastrophic

Image Source: incois.gov.in

• The Sunderbans is a mangrove ecosystem.

Answer: (a) 1, 2 and 3; Difficulty Level: Easy