Corals are animals or colonies of them that form complex seafloor structures -- the foundation for some of the richest ecosystems in the world.
Corals are slow-growing (only a few millimetres per year) and constitute a habitat of high ecological value for a wide variety of species. They create three-dimensional calcareous structures that offer protection, food and spawning areas for many animals, although these structures are very fragile.
The distribution of many coral species remains unknown today. The well known species are the ones that are commercially exploited, but there are many little known or completely unknown species with unlikely geographical distributions.
Apart from direct harvesting of some species, other factors also negatively affect coral populations, including bottom trawling and the climate change, both due to increased water temperature and increased marine acidification .