Coral reefs

Subject: Environment

Context:

• More life can be supported by ‘dead’ coral rubble than live coral, according to a recent study
• A recent study has identified new causes for coral bleaching, namely excessive nutrients from fertilisers and storm-water runoff.

Concept:

• Coral reefs are among the most diverse ecosystems in the world. They provide shelter and nourishment to fish and other marine organisms.
• Vibrant and healthy reefs form when a coral and an algae — zooxanthellae — start a symbiotic relationship.
• The coral provides protection and compounds zooxanthellae’s need for photosynthesis. The algae produces carbohydrates and helps remove the coral’s waste.
• But when the corals are stressed due to change in temperature, light and nutrients, they expel the algae and turn white. Corals will die if such bleaching extends.
• Dead’ coral reefs supported ‘cryptic’ animalse hidden sea creatures, including fishes, snails, tiny crabs and worms — who hide under this rubble to save themselves from predation.
• The general perception of life supported by ‘live’ coral reefs included larger invertebrates like starfish, giant clams and sea cucumbers.