Block of the Week: Coral

Coral blocks spawn naturally in coral reefs, found covering on the seafloor in warm ocean biomes. These reefs come in a wide variety of shapes and sizes, with coral blocks topped with coral, and sometimes coral fans and sea pickles. Brain corals form in lumps, while fire corals create beautiful, branching trees.

In order for coral blocks to stay alive, they need to be immersed in water – otherwise their beautiful colours will fade to grey. It doesn’t need a lot of water though – you can get away with just one of its sides touching a water block. Which means that you can still use it as a building material if you have a hidden irrigation system keeping it damp.

In the real world, coral reefs can also be found in warm oceans – and coral itself is actually an animal, distantly related to the jellyfish. The animals live in colonies made up of identical clones, each called a “polyp”, a few centimetres long with a mouth at one end and a hard exoskeleton at the other. Over centuries, these exoskeletons build up, and you get a reef.

It gets weirder – living algae called “zooxanthellae” grows inside the bodies of most reef-building corals. The coral gives the algae a protected environment, and all the chemicals it needs to grow, while the algae give the coral oxygen and food. It’s a win-win situation for both of them.

When the water around the coral gets too hot, however, the corals get stressed and they react by expelling the algae from their bodies. This not only makes the coral appear grey/white, or “bleached”, but it also kills the coral if it goes on too long. Unfortunately, as climate change warms our oceans, this is happening more and more often. In 1998, about 16% of the world’s reefs died. In just ten years, it’s expected that about half of the world’s coral reefs will be dead.