The genus that builds most of the reef, and the one that dies first when the water warms.
The largest genus of hard corals, growing as flat tables on a central stalk, as branching staghorn thickets, and as low bushes and plates. Colonies reach three metres across. Each polyp sits in its own cup in a shared limestone skeleton, and the tissue holds symbiotic algae that supply most of the colony’s energy.
Acropora grows faster than any other reef-building coral and is correspondingly fragile: it is the first to break in a storm, the first to bleach when water temperature rises a degree or two above the summer maximum, and the first to be lost to crown-of-thorns starfish, which prefer it. The dependent fauna is large — humbug and blue-green damselfish, coral gobies, the sixline wrasse, eightband and Meyer’s butterflyfish, coral crabs — and follows it. This entry covers the genus rather than a species; separating Acropora to species underwater is not practical and is difficult from a specimen. Recorded from the shallows to about 25 m.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
