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Coral bleaching and Great Barrier Reef

  • Posted By
    10Pointer
  • Categories
    Environment
  • Published
    18th Mar, 2020
  • Context

    • Scientists have warned that the Great Barrier Reef will face a critical period of heat stress over the coming weeks; following the most widespread coral bleaching the natural world has ever endured.
  • About the news

    • Warming ocean temperatures, a sign of climate change, is associated with the deteriorating health of the Reef.
    • The Great Barrier Reef Marine Park, which spreads across a length of over 2,300 km and is roughly the size of Italy, is home to about 3,000 coral reefs, 600 continental islands, 1,625 type of fish, 133 varieties of shark and rays and 600 types of soft and hard corals.
  • What is coral bleaching?

    • The stunning colours in corals come from marine algae called zooxanthellae, which live inside their tissues.
    • This algae provides the corals with an easy food supply thanks to photosynthesis, which gives the corals energy, allowing them to grow and reproduce.
    • When corals get stressed, from things such as heat or pollution, they react by expelling this algae, leaving a ghostly, transparent skeleton behind. This is known as ‘coral bleaching’.
    • Some corals can feed themselves, but without the zooxanthellae most corals starve.
    • Warmer water temperatures can result in coral bleaching. When water is too warm, corals will expel the algae (zooxanthellae) living in their tissues causing the coral to turn completely white.
    • Not all bleaching events are due to warm water.
  • How does it affect the Great Barrier Reef?

    • The Great Barrier Reef, which covers an area of 344,400 sq km makes up roughly 10 per cent of the world’s coral reef ecosystems. Today, the reef is a Marine Park and World Heritage Area and supports a range of activities and contributes over AUD $5.6 billion each year to the Australian economy and is also responsible for creating over 70,000 jobs.
    • In the 2019 Outlook Report prepared by the Australian government, it said that climate change was the greatest threat to the Reef. Other threats included coastal development, land-based run-off and direct human use, such as activities like illegal fishing.
    • Significantly, coral bleaching events such as the ones that took place in 2016 and 2017 have had severe impacts on the Reef, causing changes in its ecosystem. However, some parts of the reef that escaped the impact of the bleaching and cyclones still remain in good condition, the report said.
    • The 2016 bleaching caused by intense heat exposure affected the northern third region of the Reef, while the 2017 bleaching affected the central region.
    • As per the latest Reef health update, while sea surface temperatures have remained relatively stable this week (until March 5, 2020), the temperature is still above normal for this time of the year. As of March 3, most of the marine park varies between 0.5 degree-1.5 degree Celsius above normal. In some inshore areas, the temperature is 2.5-3 degrees Celsius warmer.
  • About The Great Barrier Reef

    • The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,300 kilometres over an area of approximately 344,400 square kilometres.
    • The reef is located in the Coral Sea, off the coast of Queensland, Australia.
    • The Great Barrier Reef can be seen from outer space and is the world's biggest single structure made by living organisms.
    • This reef structure is composed of and built by billions of tiny organisms, known as coral polyps.
    • It supports a wide diversity of life and was selected as a World Heritage Site in 1981.
    • Carbon pollution is causing unprecedented damage to our Great Barrier Reef.
  • Can coral recover from bleaching?

    • In some instances corals can recover from bleaching.
    • If conditions return to normal, and stay that way corals can regain their algae, return to their bright colours and survive.
    • However prolonged warmer temperatures and other stressors, like poor water quality, can leave the living coral in a weakened state.
    • It can struggle to re grow, reproduce and resist disease – so is very vulnerable to coral diseases and mortality.
    • It can take decades for coral reefs to fully recover from a bleaching event, so it is vital that these events do not occur frequently.
    • If we continue burning fossil fuels at our current rate then severe bleaching events are likely to hit reefs annually by the middle of the century.
    • This would be devastating for coral reefs as they would have no chance to recover.

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