Staghorn Coral (Acropora cervicornis)
|branches can grow to over 6.5 feet (2 m)|
|their shape resembles male deer antlers ("stag horn")|
|organic byproducts of photosynthesis; they may eat live prey, such as small fish and zooplankton, using their tentacles|
|branched colonies of Acropora have exhibited competitive behavior, gradually extended over colonies of other corals, such as Montipora|
Staghorn coral is a branching coral with cylindrical branches.
The dominant mode of reproduction for staghorn coral is asexual fragmentation, with new colonies forming when branches break off a colony and reattach to the substrate. Sexual reproduction occurs via broadcast spawning of gametes into the water column once each year in August or September. Individual colonies are both male and female (simultaneous hermaphrodites) and will release millions of "gametes".
The coral larvae (planula) live in the plankton for several days until finding a suitable area to settle, but very few larvae survive to settle and metamorphose into new colonies. The preponderance of asexual reproduction in this species raises the possibility that genetic diversity is very low in the remnant populations.
This coral exhibits the fastest growth of all known western Atlantic corals, with branches increasing in length by 4-8 inches (10-20 cm) per year. Staghorn coral has been one of the three most important Caribbean corals in terms of its contribution to reef growth and fish habitat.
How do coral eat? Tropical corals, like staghorn coral, get as much as 90 percent of their energy from the organic byproducts of photosynthesis thanks to a symbiotic relationship with algae. They may also capture and consume live prey, such as small fish and zooplankton, using their tentacles.
Some massive coral species reach sexual maturity when their colonies grow to about 4 inches (10 cm) in diameter, which occurs when they are about 8 years old. Acropora, which are faster-growing, likely reach sexual maturity at a younger age.
Staghorn coral occur in back reef and fore reef environments from 0-100 feet (0 to 30 m) deep. The upper limit is defined by wave forces, and the lower limit is controlled by suspended sediments and light availability. Fore reef zones at intermediate depths of 15-80 feet (5-25 m) were formerly dominated by extensive single species stands of staghorn coral until the mid 1980s.
We designated critical habitat for elkhorn and staghorn corals in November 2008 in four areas:
- Puerto Rico
- St. John/ St. Thomas
- St. Croix
Staghorn coral is found in the Atlantic Ocean, Caribbean Sea, and western Gulf of Mexico (non-U.S. waters). Specifically, staghorn coral is found throughout the Florida Keys, the Bahamas, the Caribbean islands, and Venezuela. The northern limit of staghorn coral is around Boca Raton, FL.
Since 1980, populations have collapsed throughout their range from various threats. Populations have declined by up to 98% throughout their range, and localized "extirpations" have occurred.
Photo: Tom Moore, NOAA
Photo: Andy Bruckner, NOAA
Photo: Andy Bruckner, NOAA
- disease, such as white band disease, is their biggest source of mortality
- algae overgrowth
- temperature and salinity variation
- asexual reproduction, allows rapid population recovery from physical disturbances such as storms, but makes recovery from disease or bleaching difficult
- low genetic diversity
Florida Keys National Marine Sanctuary (FKNMS), the largest coral reef management entity in the region, has developed a management plan for the Sanctuary's corals that includes protective activities, such as zoning and channel markings, as well as restoration efforts.
Efforts within the sanctuary to re-attach Acropora fragments generated by ship groundings and hurricane events have had mixed success. Similar efforts to re-attach coral fragments have also been made in Puerto Rico and the U.S. Virgin Islands.
Attempts to culture and settle coral larvae have also had very limited success.
New techniques for restoring Acropora, however, are currently being pursued, including:
- enhancing sexual recruitment
- reestablishing ecological roles within reef systems (e.g. herbivorous urchins)
- controlling predators and disease
In 1998, the U.S. Coral Reef Task Force was established by Presidential Executive Order 13089 to coordinate and strengthen efforts for protecting coral reef ecosystems. The Task Force is co-chaired by the Departments of Commerce and Interior, and includes leaders of 12 federal agencies, 7 U.S. states and territories, and 3 freely associated states. In 2002, the Task Force adopted a resolution calling for the development of Local Action Strategies, which are locally-driven plans for collaborative and cooperative action among federal, state, territory, and non-governmental partners to reduce key threats on valuable coral reef resources. Florida, Puerto Rico, and the U.S. Virgin Islands have developed Local Action Strategies. These strategies were implemented over a 3-year period (FY2005-FY2007).
On March 4, 2004, the Center for Biological Diversity petitioned us to list elkhorn (Acropora palmata), staghorn (A. cervicornis), and fused-staghorn (A. prolifera) coral under the Endangered Species Act (ESA). On June 23, 2004, we found that listing these species may be warranted [pdf] and initiated a formal review of their biological status. We convened the Atlantic Acropora Biological Review Team (Team) to summarize the best available scientific and commercial data available for these species in the status review report.
The Team completed the status review [pdf] on March 3, 2005. On March 18, 2005, we determined that elkhorn and staghorn corals warrant listing [pdf] as "threatened" under the ESA. However, we also concluded that listing fused-staghorn coral is not warranted, as it is a hybrid and does not constitute a "species" as defined under the ESA. On May 9, 2005, we proposed adding elkhorn and staghorn coral to the Endangered Species list [pdf].
We designated critical habitat for elkhorn and staghorn corals in November 2008.