Marine life is a huge part of why people go scuba diving and without corals, there wouldn’t be any reef life. Without our oceans, there also wouldn’t be any life on Earth. So, in this Blog we want to celebrate hard corals and reveal some facts about them that you might not know. We hope that the next time you go diving, you take a little extra time to look at the planet-saving hard corals around you! So, without further ado, here are some top facts about brain coral and other hard corals – many of which most divers don’t know!
1. There are over 3,000 species of hard corals, which are also known as stony corals, reef building corals or hexacorals. Hard corals are the frame work that forms coral reefs (hence the name ‘reef building’). One of the most common types of hard coral is brain coral (Platygyra), which is found globally. Other common types of hard coral include table corals and branching corals (Acropora) and plate corals (Monitpora) but there is a plethora of different species to be found around the world.
2. Hard corals are not plants. Corals are actually animals which are known individually as polyps. Polyps are related to anemones and jellyfish. They develop in colonies which form entire reef structures. Only hard corals can build reefs – soft corals cannot.
3. A hard coral polyp has a sac-like body and an opening, or mouth, encircled by stinging tentacles called nematocysts. The polyp uses calcium and carbonate ions from seawater to build itself a hard, cup-shaped skeleton made of calcium carbonate (limestone). This limestone skeleton protects the soft, delicate body of the polyp.
4. Most coral polyps have clear bodies. Their skeletons are white, like human bones. Generally, their brilliant colour comes from the zooxanthellae (tiny algae) living inside their tissues. Several million zooxanthellae live and produce pigments in just one square inch of coral. These pigments are visible through the clear body of the polyp and are what gives coral its beautiful colour. You only have to look at the rich pink / red colour of a brain coral to see this phenomena in action.
5. Some species of hard corals have multiple common names. For example brain coral is also known as brain worm coral, or maze coral. Plate coral is also known as leaf or lettuce coral. The common names usually directly relate to the appearance of the coral.
6. Hard corals can be affected by coral bleaching. Coral bleaching occurs when sea temperatures rise to a level which causes the coral to expel the zooxanthellae (algae). Without the algae, the coral’s white skeleton is visible, giving a bleached like effect. When coral bleaching occurs the coral is not dead and if water temperatures drop the algae will return to the coral. During bleaching periods corals are under intense stress and during a long period of bleaching some corals will not survive.
7. Did you know that corals are predators? They might not look like it but they are! Most hard corals feed at night when the polyps extend and sting passing plankton and even small fish which they pass to their mouth and ingest. Only 10% of the corals energy comes from the food it eats in this way.
8. Corals live in symbiosis with zooxanthellae. The algae which live on the coral rely on photosynthesis to produce energy, in the form of glucose (sugar). This algae derived sugar gives the coral 90% of its energy. In return, the coral provides the algae with a protected environment and compounds required for successful photosynthesis.
9. The majority of hard corals grow in warm waters at depths less than 60 meters – but there are some species of deep water corals which can tolerate temperatures as low as 3 – 4 ºC and depths of up to 2,000 meters.
10. How do corals reproduce? Corals reproduce once or twice a year, after a full moon, when there is a mass-spawning event. The polyps release eggs and sperm into the water at the same time. The eggs float to the surface and the sperm swim up to fertilize them. A few days after fertilization the newly formed embryo will sink down to the sea floor and take root as a brand new coral!
Counting Hard Corals around Nusa Lembongan, Bali
We hope you’ve learned something new about hard corals and what incredible creatures they are. When you are diving around our islands of Nusa Lembongan, Nusa Ceningan, and Nusa Penida, take time to see how many different hard corals you see in a single dive – when you start counting it’s amazing how many “new” species you’ll start to notice. Bali, and our dive sites, are positioned in the heart of the Coral Triangle which is the most marine bio-diverse area on the planet so there’s no better place to identify and learn about coral!
Are you Ready to Dive with Us in Nusa Lembongan?
Whether you are a beginner or a seasoned pro, Nusa Lembongan and Nusa Penida have something to offer everyone. If you’d like to take a PADI course while you are here we have a purpose built onsite dive training pool (above) and you’ll be amazed by the reefs, hard corals, and marine life. Imagine drifting over stunning reefs and surrounded by fish – it’s all possible!
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We are looking forward to introducing you to underwater Nusa Lembongan soon!
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