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Introduction : The article talks about the Coral reefs, its bleaching, impact and its present situation.

  • The third global coral bleaching — after events in 1998 and 2010 — in less than two decades,and the longest and most severe so far, is laying waste thousands of square kilometres of unique oceanic ecosystems.
  • The US National Oceanic and Atmospheric Administration (NOAA) rang the alarm in October 2015, and frightening images emerged last week of ghostly white corals in the Maldives.
  • In the northern section of the Great Barrier Reef, site of the largest bleaching, only 4 of 520 individual reefs are now healthy.
  • Damaged or dying reefs have been found from Réunion, off Madagascar, to East Florés,Indonesia, and from Guam and Hawaii in the Pacific to the Florida Keys in the Atlantic.
  • The longest and most severe El Niño ever has added to relentlessly warming seas, killing in weeks or months swathes of an oceanic biosphere that took up to millions of years to come into existence.

What are corals?

  • Small, soft­bodied marine organisms called polyps that live in spectacular colonies called reefs that they build using a limestone skeleton (calicle) lying at their base.
  • A polyp starts building a reef by fixing itself to a sea­floor rock, and then budding into innumerable clones that fuse into each other to create a colony that acts as one organism.
  • Corals themselves are translucent animals related to sea anemones and jellyfish, but the reefs host zooxanthellae algae, which give them a range of dazzling colours.
  • The algae have a symbiotic relationship with the polyps, capturing sunlight and carbon dioxide to make sugars that feed the polyps. The corals also feed on zooplankton and small fish.

Why do corals matter?

  • Coral reef ecosystems are less than 0.1% of the ocean area but provide food and shelter to 25% of all marine species.
  • They support fish stocks on which some 500 million people are dependent globally, including an estimated 30 million small scale fishermen and women whose livelihoods depend directly on the reefs’ survival.

What can bleaching Do?

  • With rising ocean temperatures, some bleaching is now reported every summer from across the world. In mass or global bleaching events, entire reef systems, and not just a few individual corals, bleach.
  • Mass bleaching can turn a coral dominated reef to an algae dominated one in the space of a few months — a process that can take decades or longer to reverse.
  • It is estimated that global warming, pollution and sedimentation could kill off more than 30% of the world’s reefs well before we are in the second half of this century.

The reason

    • Corals go white in warmer water: If the temperature of the ocean is just 1 degree C higher than the average summer maximum for 4 weeks, bleaching can start.
    • Strong sunshine: Excessive sunlight adds to the impact of rising ocean temperatures. It is made worse by calm seas and low tides.
    • Healthy: The brilliant colours of a healthy coral colony comes from tiny plant­like cells that live inside the clear body tissue of the animal. These plant­like algae convert sunlight into food for the corals.
    • Bleached: Heat or pollution stresses the symbiotic relationship between the polyps and the algae. As the algae turn toxic, they are expelled by the coral, resulting in the coral’s white skeleton showing through.
    • Dead: Without enough plant cells to provide the coral with food, it soon starves or becomes diseased. With time, the tissue of the coral disappears altogether, and the exposed skeleton is covered with algae.

Question: What are corals and coral bleaching? What are the reasons for it and why should we care about the growing rate of coral bleaching

Suggested Approach:

      1. Give meaning of coral and coral bleaching.
      2. The reasons for coral bleaching.
      3. The importance of coral bleaching.
      4. Some suggestions to save them.

Link: http://indianexpress.com/article/explained/corals­white­heat­2836526/

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Read 206 times Last modified on Monday, 20 June 2016 17:54
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