In warm, clear, tropical oceans lie the world's richest and most colourful marine habitats, coral reefs, the largest living structures on our planet.
But these organisms are not plants, they're animals.
Colonies of polyp invertebrates
Found in tropical ocean habitats
Depth: 0m to 60m
These vast ecosystems begin with a single coral larvae, which settles and grows on the ocean floor. In a matter of days, it transforms into a polyp.
Coral polyp – soft bodied
Corralite – hard outer skeleton
The polyp reproduces, and so a colony evolves. Polyps grow fast, but it can take thousands of years for a mature reef to develop.
Sunlight is vital for reefs, as coral polyps form a symbiotic relationship with algal plants, which live within the polyp structures.
Algae perform photosynthesis, producing food for themselves and the coral.
98% of coral's energy produced by algae
The polyps feed at night, emerging from their limestone skeletons to extract plankton from the water.
There's fierce competition for space, so when one coral detects a rival, it exudes its insides and begins to digest it.
Many other reef species exhibit symbiotic relationships. For example, crabs live and feed in coral, and in return, defend the coral from the predatory crown of thorns starfish.
Other species that feed and shelter in coral reefs include cuttlefish, harlequin shrimp, even humpback whales, which use coral reefs as breeding grounds.
Life here is remarkably diverse and inextricably linked.
Coral reefs are delicate structures. Stormy weather can destroy hundreds of years of growth in just hours.
And pollution, overfishing, and rising temperatures are destroying reefs at an alarming rate.
Coral reefs are among the world's most diverse habitats, and are vital in supporting life in our oceans.