Back-To-Back Mass Bleaching Decimates Australia's Great Barrier Reef

By Maitreyi Mantha on June 3, 2017

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Great Barrier Reef (Greatbarrierreef.org)

While U.S. President Donald Trump, who pulled out of the Paris climate agreement on June 1, is convinced global warming is a “hoax,” the deteriorating condition of the world’s coral reefs seems to suggest otherwise. Often called “rainforests of the sea,” the incredible ecosystems that occupy less than 0.1 percent of ocean’s surface are home to almost 25 percent of all marine species. Unfortunately, the rising ocean temperatures caused by global warming are wreaking havoc on these fragile organisms.

As you may know, the colorful coral reefs that we all admire, are calcium carbonate exoskeletons that provide shelter and protection to colonies of hundreds of thousands of tiny polyps that live and grow together. To survive, the sedentary animals have developed a symbiotic relationship with the zooxanthellae. The coral polyps give the algae a home in exchange for the beautiful colors and nutrition. However, when ocean temperatures rise, the coral polyps reject the zooxanthellae, losing both their food source and vivid coloring; a phenomenon researchers refer to as “bleaching.” While the tiny animals can recover from mild bleaching, they are unable to survive when it continues for an extended period.

Photo Credit: NOAA 2015B; UNDERWATER EARTH 2015

Though the warmer temperatures are impacting coral reef systems worldwide, none have been as devastated as the Great Barrier Reef, that lies off the coast of Queensland, Australia in the Coral Sea. Over the past twenty years, the beautiful ecosystem that is home to over 1,500 species of fish has suffered through four mass “bleaching” events – 1998, 2002, 2016 and now again in 2017.

The 2016 bleaching was the result of the El Niño, a natural warm weather condition which occurs periodically every 3-5 years across the equatorial Pacific Ocean. Initial aerial and in-water surveys indicated that it damaged 22 percent of the shallow water corals, the most destruction recorded in the history of the Great Barrier Reef.

Warming trend of Ocean temperatures around Australia since 1900 (Photo Credit BOM 2017C)

In March and April 2017, the ecosystem suffered a second mass bleaching event. This time around, however, there was no El Niño, and the phenomenon is entirely attributed to warmer ocean temperatures caused by climate change. Current estimates peg the damage to 500 km (310 miles) of the central portion of the reef which was largely spared last year. Additionally, a report released on May 29 found that the 2016 damage was even worse than had been previously believed, impacting an astounding 29 percent of the 2,300 km (1,400 mile) long World Heritage site reef.

To make matters worse, tropical cyclone Debbie, which could have rescued the reefs by cooling the waters, not only came in late but also added to the destruction by causing structural damage to a section which had miraculously escaped the worst of the bleaching. Marine experts say almost half of the reef is now "extremely" bleached, and 91 percent shows at least some signs of bleaching.

Bleached coral in the Great Barrier Reef (Photo Credit: Professor Peter J Mumby, University of Queensland

Given that it takes more than a decade for the bleached corals to be re-colonized by the algae after the water temperatures return to normal, researchers believe it is unlikely that the Great Barrier Reef will ever fully recover. Great Barrier Reef Marine Park Authority (GBRMPA) Chairman Russell Reichelt says, "We're very concerned about what this means for the Great Barrier Reef itself and what it means for the communities and industries that depend on it,"

While local measures such as preventing water pollution and restricting port development can help, they are not enough to save the the reef, which is already under extreme heat stress. The only solution, therefore, is a global action to reduce greenhouse gas emissions by curbing fossil fuel burning, something that the 194 countries still part of the Paris climate agreement have vowed to do. If they do not live up to their promise, we may become the only generation in history to have witnessed both the beauty and death of the largest living structure on Earth – the Great Barrier Reef!

Resources: news.nationalgeographic.com, guardian.co.uk, phys.org


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Reading Comprehension (11 questions)

  1. What did President Trump do on June 1?
  2. How much of the Earth’s surface do coral reef’s cover?

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How are corals similar to rainforests?

Vocabulary in Context

To survive, the sedentary animals have developed a symbiotic relationship with the zooxanthellae.

In the above sentence, the word sedentary most likely means:

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183 Comments
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  • drakith
    drakithFriday, June 23, 2017 at 8:25 am
    This is bad we need to help or all fish and coral will live behind glass! no more fish in the wild.
    • ofaWednesday, June 21, 2017 at 2:08 pm
      that is so cooooool i like fish
      • l_linnell_117
        l_linnell_117Saturday, June 24, 2017 at 12:41 pm
        No this not cool and if you like fish you should feel sad because their homes are dyin
        • drakith
          drakithFriday, June 23, 2017 at 9:21 am
          No its not cool the plaint is dying
        • TomTuesday, June 20, 2017 at 9:44 pm
          Come on great barrier reef stay strong!
          • scuba diverTuesday, June 20, 2017 at 10:19 am
            this is sad
            • zackaryndensmor
              zackaryndensmorMonday, June 19, 2017 at 7:36 am
              the last picture is weird
              • bedabestbb
                bedabestbbMonday, June 19, 2017 at 1:38 am
                i've been to the great barrier reef
                • ninjaFriday, June 16, 2017 at 8:35 am
                  it is home to millins of organisms so it is sad
                  • phillyFriday, June 16, 2017 at 8:34 am
                    this is supper sad and hope for no back to back to back to back to back to back event
                    • SO DOG!Wednesday, June 14, 2017 at 8:31 pm
                      lets just hope we don't have a back to back to back bleaching event
                      • SansFanWednesday, June 14, 2017 at 8:59 am
                        sucks that the coral is dieing, and all these other organisms are losing their homes.

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