Great Barrier Reef

The world's largest coral reef ecosystem, a network of nearly three thousand individual reefs and hundreds of islands stretching along Australia's northeastern coast, visible from space and built over thousands of years by colonies of tiny coral polyps depositing calcium carbonate skeletons. It supports an immense concentration of marine life, including thousands of fish species, hundreds of coral species, sea turtles and dugongs, all dependent on the reef-building corals that form the ecosystem's physical foundation. Rising ocean temperatures have triggered repeated mass coral bleaching events in recent decades, in which heat-stressed corals expel the symbiotic algae that give them both color and much of their food supply, and severe or repeated bleaching can kill the coral outright, making the reef one of the most closely monitored indicators of ocean warming worldwide. This entry describes the reef as a living ecosystem; its physical extent as a landform sits with GeographyAtlas under ruling 631.