Hump Coral

• Its largest colonies are hundreds of years old and are living organisms older than most of the trees in the region.
• Cores drilled from its skeleton are a first-rate climate archive: its annual bands record temperature, rainfall and river inputs century by century.
• It is one of the corals most resistant to warming and to sedimentation, and on many degraded reefs it is the last builder left standing.
• It forms hemispherical mounds up to six metres high and wide, and is the commonest coral species in Hawai'i.
• It grows very slowly, sometimes barely a centimetre a year, so the large colonies are extremely old.
• Its skeletons are climate archives: they lay down annual bands that are read like tree rings. Cores taken from these colonies allow sea temperature and ocean conditions to be reconstructed as far back as 400 years.
• Its polyps are barely a millimetre across. The greenish or brown colour comes from zooxanthellae, single-celled symbiotic algae that supply it with nutrients through photosynthesis.
• It has separate male and female colonies and spawns en masse around the full moon.
• It tolerates human pressure better than many corals, and in Palau lineages with greater heat tolerance have been identified.

Habitat & environment

Surf-exposed Indo-Pacific reefs, from 0 to 30 m

Sources consulted: Dana (1846); Lista Roja de la UICN; Woods Hole Oceanographic Institution; NOAA Office of National Marine Sanctuaries