Here we explore the stony corals of the Tropical Atlantic Ocean and Caribbean Sea, also known as the Caribbean Region. While this region encompasses only 1% of the ocean, it supports about 10% of all its coral reefs. These reefs are vital to the communities around them, with about 70% of the people in the Caribbean living along coasts.
The reefs in this region are fragile, and are particularly at risk due to their natural lack of diversity. While there are over 2,700 species of stony corals in the world, only 72 are represented in this region. This limited diversity leaves little room for species losses, and the current rate of decline is alarming. These corals are still vital for sustaining the health and function of the reefs and there related ecosystems and economies.
Status of Caribbean Reefs
The oldest reefs in the Caribbean sea are about 40 million years old. With he region reaching its current configuration at about 10 million years ago following the rise of the Panama which cut the region off from the Indo-Pacific. Without the flow of genetics from a larger source, diversity within the Caribbean and Atlantic has been decreasing since the late Miocene period (11.6 million to 5.3 million years ago).
With every disturbance event, coral species are lost, but there is never replacement. As such, the Caribbean reef coral assemblages are “naturally” more frail now than any other time in the last 65 million years. Additionally, human activities and rapid development in the region have led to multiple catastrophic die-off events over the last 50 years, including the outbreak of White band disease in the 1970’s. This event killed off many of the structurally complex and wave attenuating branching coral species belonging to the family Acroporidae.
The 1970’s coral disease outbreak was followed in the 1980’s by a disease affecting the long-spinned sea urchins, decimating their numbers and leading to macro-algae smothering the reefs. The culmination of both these events lead to an 80% decline in coral cover.
Subsequent bleaching and disease events, including the current outbreak of Stony Coral Tissue Loss Disease have further reduced coral abundance, with many reef building corals facing extirpation or extinction. In total, Caribbean reefs have gone from about 35% coral cover in the late 1970’s to only 15.9% in 2019. However, this decline is much greater in all US-controlled regions of the Caribbean, with none having coral cover greater than 5% as of 2019.
How Many Families of Coral are in the Caribbean and Atlantic?
There are currently 11 families of stony corals located within the Atlantic/Caribbean Region, with 1 additional family of corals (Dendrophyllidae) that is non-native to the region.
The families currently recognized (as of 2022) are listed below, with the number of extant genera listed in parentheses:
- Acroporidae (1)
- Agarciidae (3)
- Astrocoenidae (1)
- Faviidae (12)
- Montrastraea (1)
- Meandrinidae (4)
- Merulinidae (1)
- Oculinidae (1)
- Pocilloporidae (1) \
- Portidae (1)
- Rhizangiidae (1)
Guide to Caribbean Stony Corals
Acroporidae
There are only two species of extant corals within the family Acroporidae within the Caribbean region, both belonging to a single genus, Acropora. The word Acropora comes from the Greek words Akron meaning extremity or summit and porous, referring to the axial corallite at the tip of each branch
The first species in this genus is Acropora cervicornus, commonly known as Staghorn Coral and resembling the common branching corals of the Indo-Pacific. These corals are identified by long, symmetrical tapered branches (1-3cm thick) with two distinct polyp types; axial and radial.
The second, more unique species, is Acropora palmata, also known as the Elkhorn Coral. These corals form thick, rounded, or flat branches with no distinct axial polyps. Branch diameter may range from 5-25 cm, and about 1-3 cm thick.
There is also a third coral, Acropora prolifera, which used to be thought as the distinct Acropora species in the region. However, recent molecular analysis has shown it is only a hybrid of the other two.
Both Caribbean species of Acropora corals are listed as ‘Threatened’ by the US Endangered Species Act.