Staghorn Coral (Acropora cervicornis)

	Staghorn Coral (Acropora cervicornis) Photo: NOAA's Florida Keys National Marine Sanctuary

	Did You Know? · NOAA has proposed listing 66 reef-building corals under the ESA. * Comment on the proposed listing/ reclassification of corals through 04/06/3013. * Public hearing to be held on 03/12/2013. · Staghorn coral, like many corals, receive most of their energy and oxygen from symbiotic organisms called zooxanthellae. · Like counting rings in the trunk of a tree, the age of corals can be determined by examining coral growth rings.

Status
ESA Proposed Endangered - throughout its range
ESA Threatened - throughout its range

Taxonomy
Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Order: Scleractinia
Family: Acroporidae
Genus: Acropora
Species: cervicornis

Elkhorn coral is another ESA-listed species of Acropora coral.

Species Description

Length:	branches can grow to over 6.5 feet (2 m)
Appearance:	their shape resembles male deer antlers ("stag horn")
Lifespan:	unknown
Diet:	organic byproducts of photosynthesis; they may eat live prey, such as small fish and zooplankton, using their tentacles
Behavior:	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 Critical Habitat
(click for larger view PDF)

Staghorn Coral Range Map
(click for larger image)

Habitat
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.

Critical Habitat

NMFS designated critical habitat for elkhorn and staghorn corals in November 2008 in four areas:

Florida
Puerto Rico
St. John/ St. Thomas
St. Croix

Distribution
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.

Population Trends
Since 1980, populations have collapsed throughout their range from various threats, as detailed below. Populations have declined by up to 98% throughout their range, and localized "extirpations" have occurred.

Staghorn Coral
(Acropora cervicornis)
Photo: Tom Moore, NOAA

Threats

disease, such as white band disease
hurricanes
predation
bleaching
algae overgrowth
sedimentation
temperature and salinity variation
low genetic diversity

The greatest source of region-wide mortality for staghorn coral has been disease outbreaks, mainly of white band disease. Other, more localized losses have been caused by hurricanes, increased predation, bleaching, algae overgrowth, human impacts, and other factors. This species is also particularly susceptible to damage from sedimentation and is sensitive to temperature and salinity variation.

The dominant mode of reproduction for staghorn coral is asexual fragmentation; this life history trait allows rapid population recovery from physical disturbances such as storms. However, this mode of reproduction makes recovery from disease or bleaching episodes (in which entire colonies or even entire stands are killed) very difficult. The large role of asexual reproduction for this species also increases the likelihood that genetic diversity in the remnant populations is very low. Scientists are becoming increasingly concerned for this species based on its demographic paramaters; specifically, how species recruitment and genetic diversity affect recovery potential.

Staghorn Coral
(Acropora cervicornis)
Photo: Andy Bruckner, NOAA

staghorn coral thicket

Staghorn Coral
(Acropora cervicornis)
Photo: Andy Bruckner, NOAA

Conservation Efforts
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).

Regulatory Overview
On March 4, 2004, the Center for Biological Diversity petitioned NOAA's National Marine Fisheries Service (NMFS) to list elkhorn (Acropora palmata), staghorn (A. cervicornis), and fused-staghorn (A. prolifera) coral under the Endangered Species Act (ESA). On June 23, 2004, NMFS found that listing these species may be warranted [pdf] and initiated a formal review of their biological status. NMFS convened the Atlantic Acropora Biological Review Team (BRT) to summarize the best available scientific and commercial data available for these species in the status review report.

The BRT completed the status review [pdf] [4.9 MB] on March 3, 2005. On March 18, 2005, NMFS determined that elkhorn and staghorn corals warrant listing [pdf] as "threatened" under the ESA. However, NMFS 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, NMFS proposed adding elkhorn and staghorn coral to the Endangered Species list [pdf].

NMFS finalized the ESA listing of elkhorn and staghorn coral on May 4, 2006 (71 FR 26852 [pdf]). More information can be found in the press release [pdf] of the final listing.

NMFS designated critical habitat for elkhorn and staghorn corals in November 2008.

In December 2012, NMFS proposed reclassifying (77 FR 73219) the elkhorn and staghorn corals as endangered.

Key Documents
(All documents are in PDF format.)

Title	Federal Register	Date
Proposed Endangered Listing Rule Comment on Proposed Reclassification from Threatened to Endangered, extended through 04/06/2013	77 FR 73219	12/07/2012
Critical Habitat Designation	73 FR 72210	11/26/2008
Final 4(d) Rule	73 FR 64264	10/29/2008
Proposed Critical Habitat Designation	73 FR 6895	02/06/2008
Proposed 4(d) Rule	72 FR 71102	12/14/2007
ESA Listing Rule	71 FR 26852	05/09/2006
Proposed Listing Rule	70 FR 24359	05/09/2005
Status Review	n/a	03/03/2005
Proceedings of the Caribbean Acropora Workshop*	n/a	04/2002

More Information

* Bruckner, A.W., 2002. Proceedings of the Caribbean Acropora Workshop: Potential Application of the U.S. Endangered Species Act as a Conservation Strategy. NOAA Technical Memorandum NMFS-OPR-24, Silver Spring, MD 199 pp.

Updated: March 4, 2013