Elkhorn Coral
Acropora palmata

f8 @ 1/60s, Ektachrome slide film, ASA:64, Nikonos II w 15mm and Oceanic flash

"Elkhorn Coral," Wikipedia, the free encyclopedia. Elkhorn coral is considered to be one of the most important reef-building corals in the Caribbean, although current populations have been decimated by white band disease and have yet to fully recover. This species is structurally complex with many large branches. The coral structure resembles that of elk antlers. These branches create habitats for many other reef species, such as lobsters, parrot-fish, snapper shrimps and other reef fish. Elkhorn coral colonies are incredibly fast-growing, with an average growth rate of 5 to 10 cm (2.0 to 3.9 in) per year and can eventually grow up to 3.7 m (12 ft) in diameter. The color of this coral species ranges from brown to a yellowish-brown as a result of the symbiotic zooxanthellae living inside the tissue of this coral species. Zooxanthellae are a type of algae which photosynthesize to provide the coral with nutrients. The zooxanthellae are also capable of removing waste products from the coral. Historically, the majority of elkhorn coral reproduction has occurred asexually; this occurs when a branch of the coral breaks off and attaches to the substrate, forming a new colony, known as fragmentation. The degree to which local stands reproduce by fragmentation varies across the Caribbean, but on average, 50% of colonies are the result of fragmentation rather than sexual reproduction. Sexual reproduction occurs once a year in August or September when coral colonies release millions of gametes by broadcast spawning.
Salt River Canyon, St. Croix, U.S. Virgin Islands