Previous Year Question
Consider the following statements:
Most of the world’s coral reefs are in tropical waters.
More than one-third of the world’s coral reefs are located in the territories of Australia, Indonesia and Philippines.
Coral reefs host far more number of animal phyla than those hosted by tropical rainforests.
Which of the statements given above is/are correct?
1 and 2 only
3 only
1 and 3 only
1, 2 and 3
Correct Answer: D
Detailed Solution
Statement 1 is correct: Most of the world’s extensive and biodiverse coral reefs occur in tropical and subtropical marine waters.
Reef-building corals generally require shallow, clear, sunlit and warm water with normal marine salinity.
The tissues of most reef-building corals contain photosynthetic algae commonly known as zooxanthellae.
Zooxanthellae provide energy and nutrients to corals through photosynthesis, while corals provide them with a protected habitat and carbon dioxide.
Because of the requirement for sunlight, major tropical coral reefs generally develop in comparatively shallow parts of the sea.
Some corals also occur in deep and cold water, but they are different from tropical photosynthetic coral reefs.
Statement 2 is correct: More than one-third of the world’s coral reefs are located in the marine territories of Australia, Indonesia and the Philippines.
Australia’s Great Barrier Reef is the world’s largest coral-reef system.
Indonesia and the Philippines are major parts of the Coral Triangle, one of the world’s most diverse regions for corals and coral-reef fishes.
The Coral Triangle includes the marine areas of Indonesia, the Philippines, Malaysia, Papua New Guinea, the Solomon Islands and Timor-Leste.
Statement 3 is correct: Coral reefs support exceptionally high biodiversity and represent more animal phyla than tropical rainforests.
An animal phylum is a high-level taxonomic category. Marine environments contain several animal phyla that have no representatives in terrestrial environments.
Despite covering a very small part of the ocean floor, coral reefs provide food, shelter and breeding grounds to marine fishes, molluscs, crustaceans, sponges, echinoderms and numerous other organisms.
Because of this exceptional biodiversity, coral reefs are often called the rainforests of the sea.
India’s principal coral-reef regions occur in the Gulf of Kachchh, Gulf of Mannar, Lakshadweep and the Andaman and Nicobar Islands.
An increase in seawater temperature may cause corals to expel their symbiotic algae, resulting in coral bleaching.
Other major threats to coral reefs include ocean acidification, pollution, sedimentation, destructive fishing and coastal development.