Great Barrier Reef

Why in NEWS ?

• Scientists have discovered a "massive" detached coral reef in Australia's Great Barrier Reef — the first to be discovered in over 120 years.

About

• At approximately 1,640 feet(500m), it is taller than the Empire State Building.
• The reef was found on 20th October 2020 by a team conducting a year-long underwater mapping of the region's seafloor.
• The Institute's underwater robot, "SuBastian," explored the reef. The dive was livestreamed on its website.
• The scientists — who are working onboard the research vessel 'Falkor' — are presently undertaking a 12-month exploration of the ocean surrounding Australia
• The new reef is blade-like, with an almost 1-mile-wide base, it rises 1,640 feet and its peak sits about 130 feet below the ocean's surface. It is taller than the Empire State Building (1,450 feet), Petronas Twin Towers (1,480 feet) and Eiffel Tower (1,060 feet).
• It joins the seven other tall detached reefs in the area — most of which were mapped in the late 1800s. These include the reef at Raine Island — the world's most important green sea turtle nesting area.

What is the Great Barrier Reef?

• Considered to be the largest coral reef, the Great Barrier Reef reportedly covers nearly 133,000 square miles.
• The Great Barrier Reef, where this new massive reef has been discovered, is home to more than 1,500 fish species, 411 species of hard corals and dozens of other species.
• It is a world heritage site
• But the reef is facing a crisis as recent studies have shown that it has lost 50% of its coral populations in the last three decades, with climate change a key driver of reef disturbance.

What are Coral reefs?

• Coral reefs are important hotspots of biodiversity in the ocean.
• Coral reefs are the colonies of tiny living creatures that are found in oceans. They are the underwater structures that are formed of coral polyps that are held together by calcium carbonate. They consist of individual polyps that get together and build reefs.
• Coral reefs are also regarded as the tropical rainforest of the sea and occupy just 0.1% of the ocean’s surface but are home to 25% of marine species. They are usually found in shallow areas at a depth less than 150 feet. However, some coral reefs extend even deeper, up to about 450 feet.
• Coral polyps are the individual corals that are found on the calcium carbonate exoskeletons of their ancestors. Corals can be found in all the oceans but the biggest coral reefs are mostly found in the clear, shallow waters of the tropics and subtropics.
• The largest of these coral reef systems, The Great Barrier Reef in Australia, the largest coral reef is more than 1,500 miles long

Significance

• Coral reefs support a wide range of species and maintain the quality of the coastal biosphere.
• Corals control the level of carbon dioxide in the water by converting it into a limestone shell. If this process does not take place, the amount of carbon dioxide in the ocean water would increase significantly and affect ecological niches

Conditions necessary for growth of Coral Reefs

• The temperature of the water should not be below 20°C. The most favourable temperature for the growth of the coral reefs is between 23°C to 25°C. The temperature should not exceed 35°C.
• Corals can survive only under saline conditions with an average salinity between 27% to 40%.
• Coral reefs grow better in shallow water having a depth less than 50 m. The depth of the water should not exceed 200m.
• Presence of hard surface of sub-marine platform of the continental shelf or mid- oceanic ridges. Hard surface is pre condition for compaction, cementation, and solidification of unconsolidated skeletons of coral polyps.
• Water should be relatively sediment free. The high amount of sediments ends up chocking coral polyps.

Types of Coral Reefs and their distribution across India

• India has its coastline extending over 7500 kilometres. It is due to the subtropical climatic conditions, there are a very few coral reefs in India.
• Coral Reefs are differentiated into three categories based on their shape, nature and mode of occurrence.

1. Fringing Reef

• The coral reefs that are found very close to the land and forms a shallow lagoon known as Boat Channel are called Fringing Coral Reefs. The Fringing Reefs develop along the islands and the continental margins.
• They grow from the deep bottom of the sea and have their seaward side sloping steeply into the deep sea. Fringing Reefs are the most commonly found coral reefs among the three. For example Sakau Island in New Hebrides, South Florida Reef.
• Location in India- The Gulf of Mannar, The Gulf of Kutch, Palk Bay and coastline of Andaman and Nicobar Islands

2. Barrier Reef

• Barrier Reefs are considered as the largest, highest and widest reefs among the three coral reefs. They develop off the coast and parallel to the shore as a broken and irregular ring. Being the largest reef among the all, they run for 100kms and is several kilometres wide.
• Location- they are present in Indian Ocean as the Great Barrier Reef of Australia which is 1200 mile long.

3. Atolls Reefs

• An atoll can be defined as a reef that is roughly circular and surrounds a large central lagoon. This lagoon is mostly deep having a depth of 80-150 metres.
• The atolls are situated away from the deep sea platforms and are found around an island or on a submarine platform in an elliptical form. For example Fiji Atolls, Suvadivo in Maldives and Atoll of Ellice.
• Location in India- Lakshadweep reef