Coral reefs are one of the most biodiverse marine ecosystems, hosting over a million species of animals. Within that, there are over 4000 specialized reef fish which rely on the coral reef ecosystems, and hundreds of species of coral. In this article, we will be discussing some of the main types of corals.
Coral reefs
A coral reef consists of three main elements:
Hard surface
First is the hard surface, which is typically composed of submerged rocks that act as a surface for corals to attach, but also as a shelter for many coral reef animals.
Coral polyps
Coral polyps are very small, soft-bodied animals which are closely related to other marine animals, such as anemones and jellyfish. The polyps can live individually, but typically they divide into thousands of clones creating a colony, which ultimately forms the structure of the coral reef.
Reef animals
It is believed that over a million species of animals use the coral reefs, and possibly much more! The animals that use this unique ecosystem typically form symbiotic relationships, where both the coral reef ecosystem and the animals are benefitted.
16 Different Types of corals
Although there are many different species of corals, these can typically be categorized into two main groups: hard corals and soft corals. Hard corals are also known as “reef-building corals”. They have a protective limestone skeleton, known as a calicle, which builds up over time as the hard corals grow.
These hard structures form the rocky foundation upon which new coral can attach to. Soft corals more closely resemble plants and trees. As their name suggests, they are soft since they lack the calcium carbonate skeleton of their hard counterparts.
They therefore do not act as reef-building corals, instead they possess a wood-like core and a soft exterior. Similar to hard corals, they grow and live in colonies.
Soft corals
1. Pulsing Xenia
Scientific name: Xenia sp.
The Pulsing Xenia refers to a genus of soft corals, where there are several species within, that pulses and waves in the water. They closely resemble mushrooms, but their polyps grow from the top of the organism, ending in hand-like protrusions.
These hands pulse and push water around the colony. They are found predominantly around the Indo-Pacific islands.
2. Black sea rod
Scientific name: Plexaura homomalla
The black sea rod, a soft coral, grows dozens of upright branches creating a shape similar to a candelabra. It can be commonly found throughout the Florida Keys, and down to northern Venezuela. Although their polyps are mostly light browns and yellows, they get their name from the dark-colored central stalks and branches.
3. Red sea fingers
Scientific name: Alcyonium glomeratum
Found along the coasts of Great Britain and down to the Bay of Biscay, red sea fingers are locally abundant. The fingers from which they are named can reach lengths of 30cm, and can be a red or rusty color. The polyps are white, all of which possess eight tentacles, giving the colony a feather-like appearance.
4. Variable soft coral
Scientific name: Eleutherobia variabile
Like the name suggests, the variable soft coral can come in all different shapes, sizes and colors. They most commonly have a mushroom-like appearance, with variably lengthed stalks, though typically reaching lengths of up to 3 inches.
They vary mostly in their available colors, ranging from reds and pinks to whites and purples – even a combination of several colors! This species can be found along the South African coastline.
5. Sunburst soft coral
Scientific name: Malacacanthus capensis
The sunburst soft coral is another species that can be found along the South African coastline. They are bright orange in appearance, and can grow up to 6 inches. Similar to a mushroom-like shape, they possess a single stem which ends in a large bulbous protrusion.
When feeding, polyps can extend out from the top of the coral. Interestingly, when threatened the sunburst soft coral will retract the bulbous extension of the coral inside of its stem, or column.
6. Organ pipe coral
Scientific name: Tubipora musica
The organ pipe coral is found in both the Indian and Pacific Ocean. Despite being a soft coral, the organ pipe coral possesses a calcium carbonate skeleton with many tubes – like organ pipes!
Each tube contains an eight-tentacled polyp that extends from the skeleton, which quickly retracts when threatened. Organ pipe coral colonies are typically dome shaped and can reach lengths of up to 9 feet.
7. Bubblegum coral
Scientific name: Paragorgia arborea
The bubblegum coral is a large species of coral, reaching heights of up to over 18 feet. They grow branches that extend upwards and fan out in hues of red, pink and white.
Each branch has dozens of ball-like tips which resemble pieces of bubblegum. This species is known as a foundation species, which means that it can form the foundational habitat for several species within the broader ecosystem.
8. Purple sea fan
Scientific name: Gorgonia ventalina
As the name suggests, the purple sea fan is a fan-shaped soft coral found in the Atlantic Ocean and Caribbean Sea. Typically purple or white in color, it can grow up to about 5 feet tall, where the main fan grows perpendicular to the ocean currents. As a defense to potential predators, the purple sea fan contains foul-tasting structures within its skeleton which makes it unfavorable to consume.
Hard corals
9. Staghorn coral
Scientific name: Acropora cervicornis
The staghorn coral is a type of hard coral with stony cylindrical branches that can extend over 6 feet in several directions. This is an extremely important species of coral for maintaining reef growth and fish habitat. In fact, the staghorn coral is the fastest growing coral found in the western Atlantic, growing at rates of up to about 8 inches per year.
10. Table coral
Scientific name: Acropora pulchra
This hard coral species is in the same genus as the staghorn coral, as they are both types of branching hard coral. However, the table coral forms broad horizontal surfaces.
These structures have several benefits. Mainly, this increases the coral’s exposure to sunlight, which helps them maintain their symbiotic algae. This also provides a greater area for the polyp tentacles to feed on zooplankton.
11. Grooved brain coral
Scientific name: Diploria labyrinthiformis
The grooved brain coral, named so after its uncanny resemblance to a human brain, can be found in the western Atlantic Ocean and Caribbean Sea. Their hemispherical shape can reach lengths of up to 6 feet and typically have a brown or yellow coloration. They are suspension feeders (feed on organisms suspended in the water), and mainly eat zooplankton and bacteria.
12. Blue coral
Scientific name: Helioplora coerulea
The blue coral is a type of hard coral that produces a large blue skeleton made of aragonite. Blue and grey polyps live within tubes of the skeleton, adding to the distinct blue hue of this coral. Interestingly, their colonies can either be columns, plates or branches.
The blue coral has a wide distribution, found throughout much of the Indian and Pacific Ocean. Despite this, they are listed as Vulnerable by the IUCN, owed to global threats to coral reef ecosystems.
13. Pillar coral
Scientific name: Dendrogyra cylindrus
Another hard coral, the pillar coral forms large finger-like colonies that extend upwards at heights of up to 9 feet. The IUCN lists this species as Critically Endangered. They grow relatively slowly and have long life spans, despite a poor rate of juvenile survival.
They can be found throughout the warmer regions of the Atlantic Ocean and Caribbean Sea. The pillar coral is one of few coral species where the polyps can be seen extended during the day, typically to feed. The extended polyps hide the skeleton of the coral, giving it a fur-like appearance.
14. Great star coral
Scientific name: Montastraea cavernosa
The great star coral, another hard coral, is found in the Caribbean seas. They form dome-like structures of up to 6 feet in length, however, they are also known to develop plate-like structures in deeper waters.
They can be hues of red, green and brown. The great star coral polyps are very large, at several cm in diameter, and are known to expand at both the day and night.
15. Elkhorn coral
Scientific name: Acropora almata
Found in the same genus as the staghorn and table coral, the elkhorn coral is a hard coral species. It is an extremely important coral species, which provides ecosystem services by building new reefs that support a high diversity of reef-animal species. Due to the thick, elk antler-shaped branches, they also provide protection to the reef ecosystem from storms.
16. Sun coral
Scientific name: Tubastraea sp.
The name of the sun coral is derived from its solar appearance when the brightly colored polyps are extended from the stony coral. Despite the name, sun corals are not photosynthetic and are in fact nocturnal hunters.
Many species of shallow water coral rely on symbiotic algae to photosynthesize and provide the coral with energy. However, sun corals are an exception to this, and instead they extend long tentacles which allows them to capture zooplankton with their relatively large polyps.
Samantha is a wildlife biologist with degrees in animal behavior and environmental biology. Most of her work has been with reptiles, however she has also worked with birds and marine organisms as well. She enjoys hiking, snorkeling, and looking for wildlife.