Which among the following is one of the Ideal condition for the formation of Coral Reefs

The correct answer is option 4Key Points 

•  Coral reefs require warm water temperatures between 23°C - 29°C. Temperatures below 18°C inhibit coral growth.
•   Shallow waters up to 50 meters are ideal since corals depend on sunlight for photosynthesis via Zooxanthellae algae.
•   Optimal salinity for corals is 32 - 37 ppt (parts per thousand). 45 ppt is too high, causing osmotic stress.
•   Coral reefs should not be near river mouths due to freshwater dilution, increased sedimentation, and pollution, which disrupt coral growth.

Important Points

•  Temperature Sensitivity:
  • Below 18°C – Inhibits coral growth.
  • 23 - 29°C – Ideal for coral reefs.
  • Above 30°C – Can cause coral bleaching due to heat stress.
•  Depth & Sunlight:
  • Coral reefs need shallow, clear water (0 - 50 meters) for maximum sunlight penetration.
  • At 200 meters, light is too weak for coral survival.
• Salinity Factors:
  • Corals need stable salinity levels (32 - 37 ppt).
  • High salinity (above 40 ppt) leads to dehydration of coral tissues.
  • Low salinity (below 30 ppt) occurs near river mouths, harming corals.
•  River Mouths & Sedimentation:
  • Rivers bring freshwater, reducing salinity.
  • High sedimentation blocks sunlight, hindering coral photosynthesis.
  • Pollutants & nutrients from rivers can lead to algal blooms, which outcompete corals for space.

Additional Information

• Coral Reef Distribution:
  • Coral reefs are found in tropical and subtropical regions where conditions are optimal.
• Major coral reef regions:
  • Great Barrier Reef (Australia) – World's largest coral reef system.
  • Coral Triangle (Indonesia, Philippines, Malaysia) – Most diverse coral ecosystem.
  • Maldives & Lakshadweep – Atoll formations.
  • Caribbean Reefs (Belize, Bahamas) – Warm-water coral habitats.
•  Types of Coral Reefs:
  •  Fringing Reefs – Found near coastlines (e.g., Andaman & Nicobar Islands).
  •   Barrier Reefs – Separated from land by a lagoon (e.g., Great Barrier Reef).
  •   Atolls – Circular reefs surrounding a lagoon (e.g., Maldives).
  •   Patch Reefs – Small, isolated reef formations.
•  Threats to Coral Reefs:
  •  Climate Change & Coral Bleaching – Rising sea temperatures cause corals to expel Zooxanthellae, leading to bleaching.
  •  Ocean Acidification – Increased CO₂ absorption lowers pH, weakening coral skeletons.
  •  Overfishing & Coastal Development – Damages coral reef structures and reduces marine biodiversity.
  •  Pollution & Sedimentation – Industrial waste, agricultural runoff, and sewage destroy reef ecosystems.