Boulder Star Coral (Montastraea annularis) is without doubt one of the most important corals found within the Caribbean region. It dominates the reef community of the ABC islands between depths of one and 25 m (~3.3 and 82 ft). This reef-building coral is especially prolific between 10 and 20 m (~32.8 and 65.6 ft), with the largest structures found in the drop-off zone.
Not only is Boulder Star Coral most abundant within the ABC islands’ reefs, it is generally larger than other coral species. One study found it to be typically 40% larger than other coral species.
Boulder star coral colonies start off as closely packed nodules that with time become long, thick wide columns or large boulders of up to 1.5 m (~4.9 ft) in diameter. The colonies themselves can grow to become several meters wide. Living tissue, which is typically golden brown in color but can appear greyish-green, is only found on the upper part of the coral; lower parts tend to be covered in algae.
Sadly, like many coral species, the Boulder Star Coral is classified as Endangered on the IUCN Red List. There has been a severe decline in both cover and abundance of Boulder Star Coral in the past 20 years, with estimates suggesting an overall population decrease of more than 50%.
Coral disease and bleaching are the biggest threats to Boulder Star Coral. On our reefs, it is especially threatened by yellow-band disease. Curacao’s reefs have already seen a decline in Boulder Star coral colonies; in 1998 they accounted for more then 45% of all coral species as opposed to 38% in 2005.
Recovery is slow due to the species’ low recruitment rates and slow growth. However, thanks to the designation of marine protected areas throughout our islands, this coral species is now closely monitored and offered protection from a wide variety of threats. We can only hope that this will mean a bright future for Boulder Star Coral colonies within our reefs.