Mountainous star coral

Appearance

Colonies of this coral are solid and very large, forming a mound with a skirt. The surface is smooth and undulating, with small lumps, bulges or lobes. The corallites, the stony cups in which the polyps sit, are about 5 mm in diameter and cover the entire surface of the coral. The colour is usually pale brown but may be deep brown with fluorescent green highlights. This coral is part of a species complex including the closely related ''Orbicella annularis'' and ''Orbicella franksi'', but the former has more distinct nodules or small columns and the latter has a more irregular, lumpy surface.

Distribution

''Orbicella faveolata'' occurs in shallow waters in the Caribbean Sea and the Gulf of Mexico, its range including Florida, the Bahamas, Venezuela and possibly Bermuda. It is found on both the back reef and fore reef slopes of fringing reefs at depths of up to 40 m . It is often the most abundant coral species on fore reef slopes between 10 and 20 m .

Status

''Orbicella faveolata'' is a slow-growing species and the rate at which new colonies are formed is less than the rate at which mature colonies die. It is susceptible to bleaching and to several coral diseases including yellow-band disease, black band disease and plague. Numbers of individuals are believed to have declined by over 50% in the last thirty years and the International Union for Conservation of Nature lists its conservation status as being "endangered".

Behavior

Like other corals, ''Orbicella faveolata'' has a symbiotic relationship with a dinoflagellate in the genus ''Symbiodinium''. These symbionts are commonly known as zooxanthellae and large numbers are present in the coral's living tissue. Several different species of ''Symbiodinium'' associate with the coral, depending on the degree of light intensity reaching the part of the surface where they reside. When artificial shading was applied by researchers to corals for some weeks, the ''Symbiodinium'' died out in the shaded portion. When the light was restored, zooxanthellae became reinstated, but in many instances, the original species was replaced by a different species of ''Symbiodinium''.

The surface of the coral can be considered a microbiome, an ecological community of micro-organisms. The zooxanthellae, bacteria and archaea present vary with the time of year and in the spring their composition is also affected by the health of the coral and whether it is suffering from yellow-band disease.

Habitat

''Orbicella faveolata'' occurs in shallow waters in the Caribbean Sea and the Gulf of Mexico, its range including Florida, the Bahamas, Venezuela and possibly Bermuda. It is found on both the back reef and fore reef slopes of fringing reefs at depths of up to 40 m . It is often the most abundant coral species on fore reef slopes between 10 and 20 m .