Introduction Chances are you have heard of coral reefs. If you are a diver then…
The primary domain of divers is the coral reef, since most diving around the world takes place on coral reefs in the tropics. As divers we swim around reefs marveling at all the weird and wonderful creatures that surround us. While it is relatively easy to identify the fish we see around us, identification becomes a little bit trickier when faced with the enormous variety of tiny critters we see. However, when it comes to corals most of us are not very good at identifying them. These stalwarts of the ocean just hang in the background resolute in their presence, providing a home for almost all the marvelous critters that enthrall us. Scratch the surface of corals and what you discover is a magically diverse and wonderful world as complex as any other. All the different types of corals below can be found at the Similan islands.
So before we have a look at all the different types of coral, the first question is what on earth is coral? Somewhat like the classic song “is it a plant, is it a fish, is it a rock? No it’s an animal!” Yes, coral, which seems to resemble a rock or a plant is actually an animal. In fact, coral reefs are formed by a symbiosis between corals and algae (zooxanthellae) that live inside their tissues and provide the animals with by-products of photosynthesis (food), and their wonderful colors.
Find more info at coral.org
As you probably have experienced, corals come in an absolutely amazing mix of colors, shapes and sizes. Coral colors range from green, brown, pink, yellow, red, purple or blue; the exact color will depend on the exact mix of the zooxanthellae algae present within their tissues, some corals are even known to be fluorescent; these amazing color patterns are due to the incredible concentrations of algae in the coral, with several million algae present per square centimeter of coral.
Whilst there are many different types of corals, when it comes to identifying them they generally fall into one of eight different categories. Within each category there are multiple different sub types. You can find most of them at the coral reefs or the Similans
Massive corals: these are the mainstay of most reef and are boulder shaped. This category varies in size from the size of a normal egg, to and enormous two story house. They are very slow growing with growth rates of 0.5 to 4.5 cm per year.
Foliose corals: these are again among some of the most recognizable corals and are characterized by broad plate-like flaps that stick out from the underlying coral substrate. Common types of these are salad corals and leaf corals. Most of these are referred to by these names since the resemble a giant lettuce head or other leafy structures.
Table coral: again one of the most easily recognisable corals, characterised by a rising trunk and multiple fused branches that spread horizontally to create a table-like structure. These corals are one of the most commonly associated with coral bleaching and the el Niño effect.
Encrusting corals: these are some of the fastest establishing corals and are commonly seen by divers on shipwrecks and on newly sunken artificial reefs. These corals get their name from the fact that they form a crust on a substrate, and spread across the surface creating a thin colorful surface.
Elkhorn corals: as the name suggests, these types of corals resemble the branched horns of elk or deer. They tend to protrude vertically with many several off shooting side branches. The most common of these is the staghorn coral.
Digitate corals: this category of corals resembles fingers or large clumps of cigars, that have no other branches. They grow vertically and are generally not as common as most other types of corals.
Mushroom corals: as their name would suggest, these resemble the cup of a mushroom. Mushroom corals are solitary corals made up on a sole polyp than can reach up to 25 cm diameter. They generally lay on the ground, unattached. Again they are not one of the most common corals around.
Branching corals: this type is most commonly associated with the most colorful small corals, and are made up of a tree-like structure with multiple branches and secondary branches.
As with most creatures on the planet there is a great degree of variance in corals, depending on several environmental factors and the actual geographic location of the coral; the Red Sea being different to the Indo-pacific, and both being different to the Caribbean. Finally, there is some variance caused by linked genetics among the local coral population.
Learn more at: So what type of coral is the dreaded fire coral?
So why do we see white corals and what is coral bleaching?
So how does El-Nino affect corals?
Do corals have any predators?