Coral Reefs

• They are the most biologically diverse ecosystems of the planet. They are formed when Coral polyps, the animals primarily responsible for building reefs, develop a symbiotic relationship with photosynthetic algae called zooxanthellae, which live in its tissues.
• Coral reefs begin to form when free-swimming coral larvae attach to submerged rocks or other hard surfaces along the edges of islands or continents.
• The coral provides a protected environment, and the compounds zooxanthellae needs for photosynthesis.
• In return, the algae produce carbohydrates that the coral uses for food, as well as oxygen. The algae also help the coral remove waste.

Favourable conditions for formation

• Warm tropical oceans with minimum temperature of 20^oC (30^o north and 25^o south latitudes)
• Oceanic water free of sedimentation.
• Transparent parts of ocean bodies.
• Relatively low salinity ocean bodies

Types of Reef Formations

• Fringing reefs: Most common, project seaward directly from the shore, forming borders along shoreline & surrounding islands.
• Barrier reefs: Grow at border shorelines, but at greater distance. They are separated from adjacent landmass by lagoon of open, often deep water.
• Atoll: If a fringing reef forms around a volcanic island that subsides completely below sea level while coral continues to grow upward, an atoll forms. Atolls are usually circular or oval, with a central lagoon.

Distribution in India

• Gulf of Kutch: Represent northern limits of corals in Indian Ocean.
• Inter tidal areas on the West Coast of India
• Lakshadweep Islands: they represent the atoll structures.
• Gulf of Mannar
• Palk Bay
• Andaman & Nicobar Islands

Angria Bank

• A shallow submerged atoll island located 100 miles off western coast of India. Located off the coast of Ratnagiri & Sindhudurg districts, Maharashtra. This site has potential to be known as India’s Great Barrier Reef.
• The peculiarity of coral reefs present here is that it is in the middle of ocean, unlike other corals which are either coastal in nature like Gulf of Mannar or A&N island corals which are island corals.
• Angria Banks falls outside territorial waters but inside EEZ of India. Thus, it cannot be protected under Wildlife Protection Act. The area can be conserved under Maritime Zones Act.

Important Coral Types

• Fire corals are one of the rarest and most endangered species of corals.
• Snowflake coral is an invasive species of coral which has a capacity to dominate space and crowd out other marine organisms.
• Mesophotic corals: They are types of corals which can survive in low light environments. They can grow at greater depths. They normally grow between 30 and 40 meters and up to 150 meters in tropical and subtropical water.
• Pillar corals: They are found throughout the Caribbean Sea. Population of pillar coral has shrunk by 80% across its range since 1980s. The most urgent threat is Stony Coral Tissue Loss Disease which is a highly contagious diseases and has emerged in the last four years. IUCN status: Critically Endangered.

Threats

Climate change and its impact (Ocean Acidification, Ocean Warming) Destructive fishing practices, Careless tourism, Pollution, , Coral mining, Climate change.

Protection measures