Australia’s Great Barrier Reef

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 morethan 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.