Coral reefs
support 25% of
fish species
Globally, 25%
of coral reefs are
threatened
What Are Corals?
Corals are closely related to jellyfish and sea anemones. Corals are sessile (fixed in one place) animals.
A coral is a colonial organism, which means it is comprised of many polyps of identical genotype.
A polyp is a small organism that has a mouth at one end that is surrounded by tentacles. As polyps grow, new popyps grow between existing polyps, creating complex skeletal structures.
The tentacles are used for a variety of functions including capturing small creatures and defense. Corals feed using nematocysts, stinging cells, much like jellyfish. These stinging cells have a toxin that allows them to capture their prey.
They have a very delicate symbiotic relationship with microalgae (Dinoflagellates), known as zooxanthellae, that live in a symbiotic relationship within the coral host. The algae live in the protection of the coral’s digestive cavity. They use sunlight for photosynthesis and coral waste for nutrient. In return, zooxanthellae provide the coral with lipids and carbohydrates which help corals grow and build their skeletons.
Types of Coral
Coral species that build reefs are with their calcium carbonate or aragonite skeletons are known as stony corals. Common shapes of coral are: massive, tabular, branching, encrusting, foliaceous, and columnar.