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Ocean Temperature In Great Barrier Reef Hottest In 400 Years

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OCEAN TEMPERATURE IN GREAT BARRIER REEF HOTTEST IN 400 YEARS

Water temperatures in and around Australia’s Great Barrier Reef have risen to their warmest in 400 years over the past decade, placing the world’s largest coral reef under threat, according to a new study.

WHY IS THIS REPORT UNIQUE?

This research is unique, in that it puts the effects of man-made climate change in historical context. Other studies have looked at the damage to the reef over a shorter time frame.

WHAT ARE CORAL REEFS?

  • Corals are marine invertebrates or animals not possessing a spine.
  • Each coral is called a polyp and thousands of such polyps live together to form a colony, which grows when polyps multiply to make copies of themselves.
  • Corals share a symbiotic relationship with single-celled algae called zooxanthellae.
  • The algae provides the coral with food and nutrients, which they make through photosynthesis, using the sun’s light.
  • In turn, the corals give the algae a home and key nutrients. The zooxanthellae also give corals their bright colour.
  • Australia’s Great Barrier Reef is the world’s largest reef system stretching across 2,300 km.
    • It hosts 400 different types of coral, gives shelter to 1,500 species of fish and 4,000 types of mollusc.

FINDINGS OF THE REPORT

  • A group of scientists at universities across Australia drilled cores into the coral and, much like counting the rings on a tree, analysed the samples to measure summer ocean temperatures going back to 1618.
  • Combined with ship and satellite data going back around a hundred years, the results show ocean temperatures that were stable for hundreds of years began to rise from 1900 onwards as a result of human influence.
  • From 1960 to 2024, the study’s authors observed an average annual warming from January to March of 0.12 degree Celsius per decade.
  • Since 2016, the Great Barrier Reef has experienced five summers of mass coral bleaching, when large sections of the reef turn white due to heat stress, putting them at greater risk of death.

WHAT IS CORAL BLEACHING?

  • Coral Bleaching happens when corals experience stress in their environment due to changes in temperature, pollution or high levels of ocean acidity.
  • Under stressed conditions, the zooxanthellae or food-producing algae living inside coral polyps start producing reactive oxygen species, which are not beneficial to the corals.
  • So, the corals expel the colour-giving zooxanthellae from their polyps, which exposes their pale white exoskeleton, giving the corals a bleached appearance.
  • This also ends the symbiotic relationship that helps the corals to survive and grow.

CAUSES OF CORAL BLEACHING

  • Change in Ocean Temperature: Increased Ocean temperature caused by climate change is the leading cause of coral bleaching.
  • Runoff and Pollution: Storm generated precipitation can rapidly dilute ocean water and runoff can carry pollutants, which can bleach near shore corals.
  • Overexposure to sunlight: When temperatures are high, high solar irradiance contributes to bleaching in shallow water corals.
  • Extremely low tides: Exposure to the air during extremely low tides can cause bleaching in shallow corals.

 

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