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Coral Bleaching : Environment for UPSC Exams
Coral Bleaching : Environment for UPSC Exams
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Coral bleaching is the loss of endo-symbiotic algae from the coral, either through expulsion or loss of algal pigmentation.
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Above-average sea water temperatures caused by global warming have been identified as a leading cause for coral bleaching worldwide.
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Bleached corals continue to live. But as the algae provide the coral with 90% of its energy, after expelling the algae the coral begins to starve.
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Between 2014 and 2016, the longest global bleaching events ever were recorded. According to the United Nations Environment Programme, these bleaching events killed coral on an unprecedented scale. In 2016, bleaching hit 90 percent of coral on the Great Barrier Reef and killed more than 20 percent of the reef's coral.
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In 2017, the bleaching further expanded to areas of the park that were previously spared, such as the central one.
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Coral bleaching is theorized to be a generalized stress response of corals that may be caused by a number of biotic and abiotic factors, including:
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Increased or reduced water temperatures.
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Oxygen starvation caused by an increase in zooplankton levels as a result of overfishing.
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increased solar irradiance (photosynthetically active radiation and ultraviolet light)
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increased sedimentation (due to silt runoff)
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bacterial infections
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changes in salinity
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herbicides
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low tide and exposure
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cyanide fishing
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elevated sea levels due to global warming
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mineral dust from African dust storms caused by drought
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The National Institute of Ocean Technology (NIOT), Chennai, had recently deployed the ROV for studying the coral reefs of the Andaman and Nicobar Islands, which are facing survival threats due to global warming.