Most of their life is spent without movement.
The majority are classified as what is called “Hermatypic,” meaning, they have the ability to deposit hard material to aid in the stony framework of a reef.
There are two main types; Stony, and Soft:
- Soft have no exoskeleton, so they use what is called “sclerites” to reinforce their tissue.
- Stony are biocomposites of calcium carbonate.
Reef building species are found where sunlight can penetrate and where waves are stronger. This is due to the effect that waves have on them by bringing in more nutrients, food, and oxygen. Various species are found in all oceans, from tropical to polar regions.
Some actually have the ability to catch plankton and very small fish using their tentacle’s stinging cells, but most will use photosynthetic single-cells called Zooxanthellae for their nutrients. This process is what gives them their color.
Their most beloved and known behavior is their reef building ability. Otherwise, they are nearly 100% immobile.
Coral is in danger due to mining and climate change. It is believed that over 10% of the reefs in the world are now dead and 60% are considered at risk. It is possible that by 2030, nearly 50% of all reefs will be destroyed.
Some scientists use specific species, such as Bamboo Coral to identify environmental change and ocean acidification.