Elkhorn coral (Acropora palmata)

node · earth · Caribbean, Bahamas, Florida, Gulf of Mexico

The principal shallow-water reef-building coral of the Caribbean, a fast-growing branching species that built the wave-breaking reef crest across the region and, with staghorn coral Acropora cervicornis, dominated shallow Caribbean reefs for thousands of years — the fossil record shows the same species in the same zone through previous interglacials. From about 1980 white-band disease removed most of both species across their whole range within a couple of decades, one of the most complete regional collapses of a habitat-forming organism on record. Both were listed as threatened under the United States Endangered Species Act in 2006, the first corals to be listed. Their loss changed the physical reef, not only its biology: without the crest that elkhorn built, more wave energy reaches the shore behind it. This is the species most restoration nurseries in Florida and the wider Caribbean are propagating, which is why it is also the species where the limits of restoration are clearest.