Colorful world of coral reefs

Each of us has certainly seen a coral reef, but few know how it works. Corals look like plants, but they are invertebrates and belong to the cnidarians, just like jellyfish. Among other things, they are also called flower animals. Basically, two types of corals are distinguished: The stone corals and the soft corals. Stone corals have a calcareous skeleton, whereas soft corals do not. 

To feed, the corals extend their small tentacles to capture plankton. In addition, they feed on algae, which are produced by sunlight in their polyps. The corals and the algae live in a symbiosis and help each other to survive. Corals also require additional nutrients and oxygen in the water as well as an ideal temperature of 20 to 29°C. Due to global warming in recent years, the water temperature of the world's oceans continues to rise, which leads to the death of corals.

The largest coral reef on earth, the Great Barrier Reef in Australia is about the size of Germany and is several million years old. The corals on the surface are several thousand years old. Between 1985 and 2012, increased water temperatures and ocean pollution caused about 50% of the reef to die. According to estimates, the Great Barrier Reef could be almost gone by 2100.

However, the floral animals also have an important role in this complex ecosystem as food for other reef dwellers such as sea turtles, parrotfish, sea urchins and starfish.

About 5000 different coral species are known worldwide, accounting for about 1% of the ocean's area and thus being home to more than 25% of all marine life.