New Species of Black Corals

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    • Recently, five new species of black corals were discovered in the Great Barrier Reef and Coral Sea off the coast of Australia.

    About Black Corals

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    • Colonial animals: Black corals or antipatharians are colonial animals which are related to sea anemones and stony corals. 
      • They are named for the color of their stiff, black or brownish skeleton.
    • More than 150 species of black corals have been described. At least 14 species of black corals are currently known from Hawai’i. 
    • Distribution: Black corals are found in all oceans, but are most common in deep water habitats of tropical and subtropical seas. 
    • Black corals are carnivores.
    • Characteristics
      • Black corals can be found growing both in shallow waters and down to depths of over 26,000 feet (8,000 meters), and some individual corals can live for over 4,000 years.
      • Many of these corals are branched and look like feathers, fans or bushes, while others are straight like a whip.
      • Black corals are filter feeders and eat tiny zooplankton that are abundant in deep waters.
        • While colourful shallow-water corals rely on the sun and photosynthesis for energy. 
      • Similarly to shallow-water corals that build colourful reefs full of fish, black corals act as important habitats where fish and invertebrates feed and hide from predators in what is otherwise a mostly barren sea floor. 

    Major Challenges associated with Black Corals

    • In the past, corals from the deep parts of this region were collected using dredging and trawling methods that would often destroy the corals.
      • Current expeditions were the first to send a robot down to these particular deep-water ecosystems, allowing the team to actually see and safely collect deep sea corals in their natural habitats.
    • Many black corals are threatened by illegal harvesting for jewellery.  

    What are Coral Reefs?  

    • A coral reef is an underwater ecosystem characterised by reef-building corals. 
    • Formation :
      • Coral reefs are formed over a process of thousands of years. Each coral reef is made up of colonies of tiny animals called polyps
      • Each polyp produces calcium carbonate, which makes up their skeleton and protects corals internal bodies; similar to how our skeleton protects our organs. 
    • The coral polyps live in an endosymbiosis relationship with algae. Algae provides up to 90 per cent of the coral’s energy.
    • Temperature:
      • 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.
    • Salinity: Corals can survive only under saline conditions with an average salinity between 27% to 40% 
    • Shallow Water: Coral reefs grow better in shallow water having a depth less than 50 m. The depth of the water should not exceed 200m.
    • Coral reefs are divided into four classes: 
      • Fringing reefs
      • Barrier reefs
      • Atolls
      • Patch reefs. 
    • Corals are of two types: 
      • Hard corals: Hard corals extract calcium carbonate from seawater to build hard, white coral exoskeletons. Hard corals are in a way the engineers of reef ecosystems and measuring the extent of hard coral is a widely-accepted metric for measuring the condition of coral reefs.
      • Soft corals: Soft corals attach themselves to such skeletons and older skeletons built by their ancestors. Soft corals also add their own skeletons to the hard structure over the years. These growing multiplying structures gradually form coral reefs.
    • Bleached corals can survive depending on the levels of bleaching and the recovery of sea temperatures to normal levels. 

    Australia’s Great Barrier Reef (GBR)

    • The reef is located in the Coral Sea, off the coast of Queensland, Australia.
    • This reef was selected as a World Heritage Site in 1981.
    • A large part of the reef is protected by the Great Barrier Reef Marine Park.

    Source: TH