Written by Tom Hooper
Some huge colonies which reach the size of a car are thousands of years old.
The corals on the reef slopes of Rodrigues are in very good condition, with around 140 different species of coral represented. Compared with places such as Indonesia or the Great Barrier Reef, this biodiversity is quite low. A coral reef is made up of countless individual animals called polyps. These invertebrate animals manufacture their skeleton from calcium in the seawater.
The following species are commonly found in Rodrigues:
This is the fastest-growing coral. With a very light and delicate skeleton the fingers of some branching shapes can grow 10cm a year. This group has a wide variety of shapes with forms which are branching, mounds, fingers and flat plates.
This coral grows in huge mounds known as ‘massive’ formations. When alive it is a brown or green colour. Its polyps are translucent and come out at night to feed. They are very sensitive and can quickly retract back into the skeleton if they sense movement such as a fish about to take a nip of their tentacles.
These are called mushroom corals as they resemble field mushrooms with their disc shapes and radiating vanes. This coral has only one polyp with many bright green tentacles. Unlike other corals, this one does not stay cemented to the reef, but is free living and will be moved around by the waves.
One of the toughest corals and is often found in places where other corals cannot survive. It can tolerate long exposure to the sun and muddy conditions. The skeleton looks a bit like honeycomb.
Has a form which resembles leaves. The corallites are on both sides and have a very clear spider shape. They are brown in colour and are often found in muddy habitats such as around the channel at Port Mathurin, which is quite unusual for corals.
A coral with very fine branches. Sometimes these corals are a beautiful pink colour. Their bumpy corallites can look like popcorn!
This group are often large, rounded and dense balls. They are very slow growing, with a coral taking up to 50 years to reach the size of a football. Some huge colonies which reach the size of a car are thousands of years old and are sometimes cored to yield climatic information.
These corals live all around the tropics. Their larvae can travel for hundreds, if not thousands, of miles.