Previous Year Question

Coral Bleaching is a process in which corals lose the Symbiotic Algae living within their tissues due to environmental stress, causing them to turn white or extremely pale. Corals are marine animals belonging to Phylum Cnidaria, and their tissues contain photosynthetic algae known as Zooxanthellae. These algae provide energy to corals through Photosynthesis and contribute to their coloration. The increase in seawater temperature caused by Global Warming is the principal driver of widespread coral bleaching.

Tropical corals generally develop within a limited temperature range. When seawater temperatures rise approximately 1–2°C above the normal local summer maximum and remain elevated for a sustained period, corals may experience Thermal Stress. This disrupts photosynthesis and nutrient exchange between corals and their symbiotic algae. Consequently, corals may expel the algae, or the algae may lose their photosynthetic pigments. As the algae decline, the white Calcium Carbonate (CaCO₃) skeleton beneath the coral tissues becomes visible.

Coral Bleaching does not necessarily mean the immediate death of corals. If seawater temperatures return to normal and environmental stress decreases, corals may regain their symbiotic algae and recover. However, prolonged exposure to high temperatures or repeated bleaching events can cause energy deficiencies, reduced growth and reproductive capacity, and increased susceptibility to diseases. Under severe conditions, coral mortality can affect the natural habitats of fish and other marine organisms dependent on Coral Reefs.

Coral Mining, Coral Diseases, and Sedimentation also damage coral reef ecosystems. Mining causes direct physical damage to coral reefs, whereas sediment accumulation can reduce sunlight availability and cover coral surfaces. Diseases may also cause coral mortality or tissue deterioration. Although some of these local stresses can induce bleaching, the primary cause of widespread Mass Coral Bleaching is an abnormal increase in seawater temperature. In India, Lakshadweep, the Andaman and Nicobar Islands, the Gulf of Mannar, and the Gulf of Kutch are major coral reef regions.