Underwater photograph of elkhorn coral.

About The Species

Elkhorn coral is one of the most important corals in the Caribbean.  It, along with staghorn coral and star corals (boulderlobed, and mountainous), built Caribbean coral reefs over the last 5,000 years. Elkhorn coral can form dense groups called “thickets” in very shallow water.  These provide important habitat for other reef animals, especially fish.

In the early 1980s, a severe disease event caused major mortality throughout its range and now the population is less than 3 percent of its former abundance. The greatest threat to elkhorn coral is ocean warming, which cause the corals to release the algae that lives in their tissue and provides them food, usually causing death. Other threats to elkhorn coral are ocean acidification (decrease in water pH caused by increased carbon dioxide in the atmosphere) that makes it harder for them to build their skeleton, unsustainable fishing practices that deplete the herbivores (animals that feed on plants) that keep the reef clean, and land-based sources of pollution that impacts the clear, low nutrient waters in which they thrive.

NOAA Fisheries and our partners are dedicated to conserving and recovering the elkhorn coral populations throughout its range. We use a variety of innovative techniques to study, protect, and restore these threatened corals. We engage our partners as we develop regulations and management plans that foster healthy coral reefs and reduce the impacts of  climate change, unsustainable fishing, and land-based sources of pollution.

Status

Elkhorn coral used to be a dominant coral on Caribbean reefs and was so abundant that an entire reef zone is named for it. Beginning in the 1980s, the elkhorn coral population declined 97 percent from white band disease. This disease kills the coral’s tissues. 

White band disease affecting elkhorn coral.

White band disease affecting elkhorn coral. Photo: Jez Roff (CC BY-SA 3.0)

Currently, there are locations such as the U.S. Virgin Islands where populations of elkhorn coral appear stable at low abundance, and some such as the Florida Keys where population numbers appear to be decreasing. Successful reproduction is very rare, so it is hard for elkhorn coral populations to increase.

ESA Threatened

throughout its range

CITES Appendix II

throughout its range

Appearance

Elkhorn coral colonies are golden tan or pale brown with white tips and they get their color from the algae that lives within their tissue. Elkhorn corals have frond-like branches, which appear flattened to near round, and typically stem out from a central trunk and angle upward. Branches are up to 15 inches wide and range in thickness from 1 to 2 inches. Individual colonies can grow to at least 6 feet in height and 12 feet in diameter. Elkhorn coral colonies can grow in dense stands and form an interlocking framework known as thickets. Each elkhorn coral colony is made up by many individual polyps that grow together. Each polyp is an exact copy of all the polyps on the same colony.

Behavior and Diet

Elkhorn coral get food from photosynthetic algae that live inside the coral's cells. They also feed by capturing plankton with their polyp’s tentacles. Coral bleaching is the loss of the algae that live in coral tissue. This loss can lead to coral death through starvation or increased vulnerability to diseases.

Due to their tree-like growth form, elkhorn corals provide complex habitat for fish and other coral reef organisms.  When elkhorn corals are abundant, they provide shoreline protections from large waves and storms.

Location Description
Elkhorn coral is found typically in clear, shallow water (1 to 15 feet) on coral reefs throughout the Bahamas, Florida, and the Caribbean. The northern extent of the range in the Atlantic Ocean is Broward County, Florida, where it is relatively rare (only a few known colonies). Elkhorn coral lives in high-energy zones, with a lot of wave action. Too much wave action (major storms) can cause this branching coral to break. However, fragmentation via branch breakage is one method of reproduction for elkhorn coral.

NOAA Fisheries has designated four critical areas determined to provide critical recruitment habitat for elkhorn corals off the coast of Florida and off the islands of Puerto Rico and the U.S. Virgin Islands.
Elkhorn coral range map.
Lifespan and Reproduction

Elkhorn coral reaches reproductive maturity at about 2 square feet. Elkhorn coral is a simultaneous hermaphrodite, meaning each colony produces both eggs and sperm but usually does not self-fertilize. Elkhorn coral sexually reproduces once per year after the full moon in late summer by “broadcast spawning” eggs and sperm into the water column. Fertilized eggs develop into larvae that settle on hard surfaces and form new colonies.  Elkhorn coral can also form new colonies when broken pieces, called fragments, re-attach to hard surfaces. Elkhorn coral is one of the fasted growing corals—when healthy, it can grow up to 5 inches in branch length per year.

Diagram depicting lifecycle of Acropora corals.

Life cycle of Acropora spp. Credit: NOAA Fisheries.

Threats

Climate Change

Climate change is the greatest global threat to corals. Scientific evidence now clearly indicates that the Earth's atmosphere and oceans are warming, and that these changes are primarily due to greenhouse gases derived from human activities.  As temperatures rise, mass coral bleaching events and infectious disease outbreaks are becoming more frequent. Additionally, carbon dioxide absorbed into the ocean from the atmosphere has already begun to reduce calcification rates in reef-building and reef-associated organisms by altering seawater chemistry through decreases in pH. This process is called ocean acidification

Diseases

Diseases can cause adult mortality, reducing sexual and asexual reproductive success, and impairing colony growth. Coral diseases are caused by a complex interplay of factors including the cause or agent (e.g., pathogen, environmental toxicant), the host, and the environment. Coral disease often produces acute tissue loss. Elkhorn coral is particularly susceptible to white band and white plague diseases.

Unsustainable Fishing Pressure

Fishing, particularly unsustainable fishing, can have large scale, long-term ecosystem-level effects that can change ecosystem structure from coral-dominated reefs to algal-dominated reefs (“phase shifts”). This results from the removal of fish that eat algae and keep the reef clean to allow for space for corals to grow.  

Land-Based Sources of Pollution

Impacts from land-based sources of pollution—including coastal development, deforestation (clearing a wide area of trees), agricultural runoff, and oil and chemical spills—can impede coral growth and reproduction, disrupt overall ecological function, and cause disease and mortality in sensitive species. It is now well accepted that many serious coral reef ecosystem stressors originate from land-based sources, most notably toxicants, sediments, and nutrients.

Scientific Classification

Kingdom
Animalia
Phylum
Cnidaria
Class
Anthozoa
Order
Scleractinia
Family
Acroporidae
Genus
Acropora
Species
palmata

What We Do

Conservation & Management

We are committed to the protection and recovery of elkhorn coral through implementation of various conservation, regulatory, and restoration measures. Our work includes:

  • Protecting habitat and designating critical habitat.

  • Breeding elkhorn corals in nurseries and planting them into the wild.

  • Increasing elkhorn coral resilience to climate change.

  • Rescuing injured elkhorn corals after ship groundings or major storm events.

Science Behind the Scenes

We conduct various research activities on the biology, behavior, and ecology of elkhorn coral.  The results of this research are used to inform management decisions and enhance recovery efforts for this threatened species. Our work includes:

  • Tracking individuals over time to understand population trends and causes of death.

  • Conducting spawning observations and collection of eggs and sperm for culturing elkhorn coral larvae.

  • Conducting temperature and acidification experiments on eggs, sperm, larvae, and newly settled colonies.

  • Conducting experiments to enhance the success of elkhorn coral propagation efforts.

How You Can Help

Conserve energy

Conserve Energy

Use energy efficient lighting, bike to work, or practice other energy saving actions to reduce greenhouse gas emissions. Climate change is one of the leading threats to coral reefs.

Learn more about climate and corals >

Conserve water

Conserve Water

The less water you use, the less runoff and wastewater carrying nutrients, sediments, and toxins into the ocean.

Learn how toxins and other pollutants affect coral reefs >

Practice safe boating

Practice Safe Boating

Anchor in sandy areas away from coral and obey aids-to-navigation/signage to make sure you do not accidentally injure corals that are just below the surface.

Be reef smart >

Reduce chemical/sunscreen pollution

Reduce Chemical/Sunscreen Pollution

Choose sunscreen with zinc oxide or titanium dioxide over those containing oxybenzone, which is toxic to corals.

Learn more about what you can do to protect coral reefs >