Which natural reef system is the largest coral reef ecosystem in the world?

The Great Barrier Reef is the largest coral reef ecosystem in the world.

It lies off the northeastern coast of Australia, beside Queensland, and extends for roughly 2,300 kilometres. The system includes thousands of individual reefs and hundreds of islands, rather than being one continuous wall of coral. Its organisms build limestone structures that grow over long periods in shallow, sunlit seawater.

The reef supports an extraordinary variety of marine life, including corals, fish, turtles, dolphins, seabirds and dugongs. It is protected through the Great Barrier Reef Marine Park and was listed as a UNESCO World Heritage Site in 1981.

Coral bleaching occurs when stressed corals expel the microscopic algae that provide much of their energy and colour. Rising ocean temperatures are a major threat, along with pollution, storms and crown-of-thorns starfish outbreaks. The reef is therefore both a spectacular ecosystem and a sensitive indicator of ocean health.