What is the Great Barrier Reef?

1 min read
What is the Great Barrier Reef? Blog Image


A UNESCO heritage committee recently stopped short of listing Australia’s Great Barrier Reef as a site that is “in danger” but warned the world’s biggest coral reef ecosystem remained under “serious threat” from pollution and the warming of oceans.

About Great Barrier Reef:


  • Location: It lies in the Pacific Ocean off the northeastern coast of Queensland, Australia, in the Coral Sea.
  • It is the longest and largest coral reef system in the world. 
  • Size:
    • It extends in roughly a northwest-southeast direction for more than 2,000 km, at an offshore distance ranging from 16 to 160 km, and its width ranges from 60 to 250 km. 
    • It has an area of some 350,000 square km.
  • It is composed of over 2,500 individual reefs of varying sizes and shapes and over 900 islands.
  • It was designated as a UNESCO World Heritage Site in 1981.
  • Much of the Great Barrier Reef is a marine protected area, managed by the Great Barrier Reef Marine Park Authority of Australia.
  • Biodiversity: It is estimated that the reef is home to around 1,500 species of fish and around 600 different coral species.


Key Facts about Corals:

  • Corals are marine invertebrate animals that belong to the phylum Cnidaria.
  • Coral Polyps:
    • Corals exist as individual polyps, which are small, sac-like organisms with a mouth surrounded by tentacles.
    • The polyps secrete a hard external skeleton made of calcium carbonate, which forms the basis of the coral structure.
  • Colony:
    • Most polyps live in groups of hundreds to thousands of genetically identical polyps that form a ‘colony’.
    • The colony is formed by a process called budding, which is where the original polyp literally grows copies of itself.
  • Symbiotic Relationship:
    • Many corals have a symbiotic relationship with single-celled algae called zooxanthellae.
    • These algae live within the coral's tissues and provide them with essential nutrients through photosynthesis.
    • In return, the corals offer protection and a place to thrive in well-lit, shallow waters.
  • What are Coral Reefs?
    • Coral polyps secrete a hard skeleton made of calcium carbonate, which over time forms the reefs.
    • Coral reefs are therefore created by millions of tiny polyps forming large carbonate structures.
  • Coral Bleaching:
    • When stressed by high temperatures, pollution, or other factors, corals expel their zooxanthellae, leading to coral bleaching.
    • Without their symbiotic algae, corals lose their vibrant colors and become more vulnerable to disease and mortality.


Q1) What is algae?

Algae are a diverse group of photosynthetic organisms that are found in all types of aquatic environments, including oceans, lakes, rivers, and even moist soil. They can be single-celled or multicellular, and they come in a wide variety of shapes and sizes. Like plants, algae are photosynthetic, meaning they use sunlight to convert carbon dioxide and water into energy-rich organic compounds like sugars. This process releases oxygen as a byproduct, contributing significantly to the Earth's oxygen production.

Source: UNESCO recommends to take Great Barrier Reef off danger list, still warns of ‘serious threat’