Blue coral is a type of stony coral commonly found in tropical reef flats or slopes in the southern hemisphere of the pacific ocean. This coral gets its name from the blue color of its skeleton, which also makes it highly desirable in the tourist trade. The scientific name for blue coral is Heliopora coerulea.
Although coral often looks more plant-like, it is actually an animal. The hard bony structures people commonly associate with coral is actually the skeleton which is secreted by the polyps, the moving parts of the coral. Each polyp's skeleton is joined to others, creating a colony. Like most stony corals, in blue coral, the polyps are small. Each polyp has a truck on one end, which is attached to the colony, and eight tentacles around its mouth opening on the other end.
Blue coral is found near the coast of Australia, Japan, and Indonesia, as well as parts of Africa and India. It is also, rarely, found around Fiji. It usually lives in shallow waters, less than 6.6 feet (2 m) deep. Colonies vary in size, but some may reach over 6 miles (10 km) across. When viewed along with the surrounding environment, a colony is usually called a coral reef, which provides a habitat to a wide variety of animals and plants.
Like most coral, blue coral is a hermatypic coral. Hermatypic corals live in symbiosis with algae called zooxanthellae, which inhabit the coral's tissue, enjoying the protection of the colony. Although the coral is not capable of photosynthesis, the algae are, and the nutrients produced are shared between the algae and the coral.
Blue coral reproduces sexually. Called brooding, a polyp will grow one or two larvae inside eggs within its body. Once hatched and outside the polyp, the larvae will attach to the colony. Larvae cannot swim, so any movement away from the parent polyp is due to ocean currents.
Although blue coral is often considered common in the areas it is found, like most coral, it is threatened by the pollution and overfishing which often causes the destruction of delicate reef environments. In addition, this coral is also harvested for trade. Made into jewelry or used in aquariums, blue coral was harvested extensively in the late 1980s throughout most of the 1990s. Now may colonies are found in protected areas of the ocean, which limits the destruction of their environments, but many are still harvested for trade.