Pillar coral  (Dendrogyra cylindrus)

Classified as Vulnerable (VU) on the IUCN Red List (1).

The beautiful pillar coral obtains its common name from the tall, pillar-like spires that grow upwards from a broad base (2) (3). These tall pillars, reaching up to three metres in height (2), often have a bristly appearance when the drab, olive-coloured polyps are open during the daytime (2) (4).

Dendrogyra cylindrus is found in the West Atlantic, mainly around the Caribbean islands, although it also grows in the southern Gulf of Mexico and around the coast of Florida and the Bahamas (1).

Dendrogyra cylindrus is a marine species, which grows on flat or gently sloping reefs. It can occur at depths between 1 and 25 metres, although is most commonly found at depths between 5 and 15 metres (1).

Dendrogyra cylindrus has a special symbiotic relationship with algae, called zooxanthellae. The zooxanthellae live inside the tissues of the coral and provide the coral with as much as 90 percent of its energy requirements, which it produces through photosynthesis. In return, the coral provides the zooaxanthellae with protection, shelter and a constant supply of the carbon dioxide required for photosynthesis (5) (8).

The slow-growing Dendrogyra cylindrus reproduces in two ways, both sexually and by fragmentation (6) (7). In fragmentation, when pillar colonies are toppled by storms or simply fall over, new pillar columns will start growing from along the length of the horizontal fallen pillar (7). When reproducing sexually, the coral releases sperm and eggs into the water, where fertilisation takes place, and the resultant larvae may be transported for great distances before settling on the substrate (8). Unlike many other corals which are hermaphroditic, the sexes are separate in the pillar coral, meaning that there are both male individuals (which release sperm) and female individuals (which produce eggs) (7). 

Global climate change is a potentially devastating threat to all coral species, causing an increase in ocean temperatures, rising acidity levels, and more severe storms. These changes result in coral bleaching, in which the zooxanthellae are expelled, leaving the coral weak and vulnerable to an increasing variety of harmful diseases (1). One disease that specifically affects the uncommon Dendrogyra cylindrus is white plague, which is caused by the bacterium Aurantimonas coralicida and results in partial mortality of individual colonies (1) (8).

Unfortunately, this species has a low rate of juvenile survivorship, meaning that it is slow to recover from disturbances, such as fisheries, human development, pollution, and invasive species, placing its future survival at even greater risk (1).

Dendrogyra cylindrus occurs within a number of Marine Protected Areas, such as Florida Keys National Marine Sanctuary (1), which will hopefully provide some protection from human-caused disturbances. In addition, like all corals, it is illegal to harvest this species for commercial purposes in USA waters (1).

In order to ensure the long term survival of Dendrogyra cylindrus, it is important to understand more about it. Research into its population status, ecology and habitat, as well as its threats and resilience to threats, are all important factors which need to be taken into consideration when planning conservation efforts for this species (1).

To learn about efforts to conserve Dendrogyra cylindrus see:

• EDGE of Existence:
  http://www.edgeofexistence.org/coral_reef/species_info.php?id=1838

For further information on the conservation of coral reefs see:

• Reef Check:
  http://www.reefcheck.org
• The Coral Reef Alliance:
  http://www.coralreefalliance.org