Blue coral (''Heliopora coerulea'') is a species of colonial

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and ...

. It is the only

octocoral Octocorallia (also known as Alcyonaria) is a class of Anthozoa comprising around 3,000 species of water-based organisms formed of colonial polyps with 8-fold symmetry. It includes the blue coral, soft corals, sea pens, and gorgonians (sea fan ...

known to produce a massive skeleton. This skeleton is formed of

aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including pre ...

, similar to that of

scleractinia Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a ...

. Individual

polyps A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral (opposite to oral) end i ...

live in tubes within the skeleton and are connected by a thin layer of tissue over the outside of the skeleton.

Description

The blue coral is the only extant

with a massive skeleton, which is composed of fibrocrystalline

(calcium carbonate). It is a hermatypic

zooxanthellae Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus ''S ...

te species with either blue or grey-grey polyps located within its skeleton, which each contain eight tentacles. Its colonies are either columnar, plates or branched. It is a tolerant species and is used in

marine aquarium A marine aquarium is an aquarium that keeps marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only (FO), fish only with live rock (FOWLR), and reef aquaria. Fish only tanks ofte ...

s. Iron salts give the skeleton of ''Heliopora coerulea'' its unique color, which allows for easy recognition in fossil outcrops. As such, it is fairly abundant within

paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

, with fossils indicating the species has remained unchanged since the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

. Blue coral has shown a particular resistance to thermal changes in their environments and have actually grown more in warmer temperatures. Image:Heliopora coerulea, Samoa Americana.jpg, Live colony Image:Heliopora coerulea, Samoa.jpg, Close-up on live polyps (notice the 8 arms) Image:Heliopora coerulea (YPM IZ 010737.CN).jpeg, Preserved skeletton, showing the typical color Image:Blue coral - Heliopora coerulea.jpg, ''idem'' Image:Heliopora coerulea (MNHN-IK-2000-348) 001.jpeg, Close-up.

Distribution

Despite being common in some areas and having a large range, the blue coral has been given the conservation status of a

vulnerable species A vulnerable species is a species which has been categorized by the International Union for Conservation of Nature as being threatened with extinction unless the circumstances that are threatening its survival and reproduction improve. Vulnera ...

by the IUCN. Its population is unknown but it is believed to be decreasing in line with the global destruction of coral reefs; it is threatened by aquarium harvesting, bleaching,

habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

, the

acidification Acidification may refer to: * Ocean acidification, decrease in the pH of the Earth's oceans * Freshwater acidification, atmospheric depositions and soil leaching of SOx and NOx * Soil acidification, buildup of hydrogen cations, which reduces the ...

of oceans, and climate change. It is found in the eastern and western Indian Ocean, and the eastern central, western central, northwestern, and southwestern Pacific Ocean; its range includes the Great Barrier Reef, Australia, Japan and the

Ryukyu Islands The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Taiwan: the Ōsumi, Tokara, Amami, Okinawa, and Sakishima Islands (further divided into the Miyako and Yaeyama Islands), with Yona ...

. Its largest colony is believed to be located off

Ishigaki Island , also known as ''Ishigakijima'', is a Japanese island south-west of Okinawa Hontō and the second-largest island of the Yaeyama Island group, behind Iriomote Island. It is located approximately south-west of Okinawa Hontō. It is within the ...

in the

Yaeyama Islands The Yaeyama Islands (八重山列島 ''Yaeyama-rettō'', also 八重山諸島 ''Yaeyama-shotō'', Yaeyama: ''Yaima'', Yonaguni: ''Daama'', Okinawan: ''Yeema'', Northern Ryukyuan: ''Yapema'') are an archipelago in the southwest of Okinawa P ...

, southwestern Japan. It is found in reefs with depths below 2 m, or reefs exposed to waves, flats, intertidal regions, and sometimes in marginal habitats. The blue coral is listed under Appendix II of

CITES CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...

. The world's largest deposit of blue coral is in Shiraho, Japan.Claus, C. A. 2020. Drawing the Sea Near: Satoumi and Coral Reef Conservation in Okinawa. Minneapolis: University of Minnesota Press This deposit however was threatened by the possible development of an airport in 1989. The airport was to be placed over the coral bed and would have resulted in the destruction of these rare coral. Transnational organizations such as the World Wide Fund for Nature stepped in and with public support managed to prevent the construction. The organization also constructed a field research station at the site to further study the corals. The airport was eventually built but at a location where it wouldn't harm the corals. The Fund then attempted to implement their typical procedures of creating protected areas for the coral. However, the prior support from the public disappeared. The residents of Shiraho were opposed to the creation of such areas. Conservationists thus took a different approach. They attempted to further connect the community of Shiraho with the sea, beyond just fishing, to try and inspire a desire to conserve the area. What resulted was the revitalization of sanizu. It is a local celebration where the people give back to the sea gods. The tradition had decreased in prevalence over the years due to a variety of reasons including economic pressure and other local socioeconomic conditions. The Fund was unable to initiate the celebration so instead they provided the tools and resources for it. This led to a large-scale sanizu celebration where both locals and conservationists connected with the sea.

Taxonomy

''Heliopora coerulea'' was described by Pallas in 1766.

References

External links

* {{taxobar, from=Q1056942 Helioporidae Corals described in 1766 Taxa named by Peter Simon Pallas