Staghorn coral

Photograph by Joel Sartore, National Geographic Photo Ark
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Staghorn corals can be found in shallow tropical reefs, slopes, and lagoons. Climate change threatens the survival of these corals as it disturbs their symbiotic relationship with algae.

Photograph by Joel Sartore, National Geographic Photo Ark

What is the staghorn coral?

Like its name suggests, staghorn coral is a species of coral that looks a bit like the antlers of a male deer. Capable of growing into thickets up to five feet high and more than 30 feet across, staghorn corals produce long, cylindrical branches out of bases anchored to the ocean floor.

Staghorn corals can grow up to two inches a year, making it relatively fast-growing. Colors range from dark gray and brown to more vibrant pinks, purples, and blues.

Acropora muricata was formerly known as Acropora formosa. It should also be noted that there are other species commonly referred to as “staghorn coral,” including Acropora cervicornis, which is native to Florida and the Caribbean.

Habitat and diet

Staghorn corals occur in shallow tropical reefs, slopes, and lagoons from Israel and Jordan to the eastern coast of Africa and all the way out to islands in the Pacific, such as Vanuatu and Kiribati. The animals prefer water depths between 15 and 100 feet.

Like other corals in the Acropora genus, staghorn corals use tiny, stinging tentacles to snatch and eat small aquatic animals known as zooplankton. Staghorn corals are also nocturnal predators, waiting until the sun goes down before they unfurl their tentacles and start hunting.

Acropora corals are also known to harbor Symbiodiniaceae, a family of algae that creates nutrients for the coral by converting sunlight into energy by way of photosynthesis. In exchange, the algae get a place to live and protection from predators. This is what scientists call a symbiotic relationship.

Threats to survival

Climate change is one of the biggest threats facing all coral species today, and staghorn corals are no exception.

Higher than normal water temperatures cause coral to evict their symbiotic algae, which affects how much energy they can create. Removal of algae also turns corals white, a phenomenon commonly known as bleaching. While the coral remains alive in this ghostly state, bleaching renders it more susceptible to stress and disease.

Unfortunately, staghorn corals seem to have a particularly low resistance and tolerance to bleaching and can take even longer to recover than other species.

To make matters worse, coral diseases are also on the rise in the Indo-Pacific. Some studies have found links between warming surface temperatures and disease outbreaks.

Staghorn corals are also vulnerable to certain predators, like the crown-of-thorns starfish (Acanthaster planci), which have proliferated since the 1970s. In large numbers, crown-of-thorns starfish can mow down wide swaths of coral reef.

The International Union for Conservation of Nature (IUCN) reports that Acropora species are in the top three genera collected for the aquarium trade. This suggests unsustainable harvesting could also harm the species.

Conservation

The IUCN considers staghorn corals to be near threatened. The good news is that at least one study has found that this species can be successfully transplanted to new areas. In the future, this could mean scientists may be able to help reestablish the species in areas where it has disappeared.

While this species is not the focus of any targeted conservation plans, staghorn corals do occur in areas that have already been designated as protected. Researchers like National Geographic grantee David Obura, founding director of Coastal Oceans Research and Development—Indian Ocean (CORDIO) East Africa, are also investigating the threats facing all reef-building corals. Scientists recommend future research focus on the staghorn’s life cycle, habitat, and ability to withstand all of the numerous threats it faces. Captive breeding techniques may also one day be critical to the species’ survival, should staghorn coral populations continue trending downward.

Furthermore, better regulation and oversight of the aquarium trade could help prevent too many staghorns being removed from the wild.

Coral Reefs 101 What are coral reefs? Coral can be found in tropical ocean waters around the world. But how much do you know about reefs and the tiny animals—polyps—that build them? Learn all about coral and why warming waters threaten the future of the reef ecosystem.