Biology
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Blue corals are hermatypic corals, and therefore have microscopic algae (zooxanthellae) living within their tissues. Through photosynthesis, these symbiotic algae produce energy-rich molecules that the coral polyps can use as nutrition (3). In return, the coral provides the zooxanthellae with protection, and access to sunlight.
Blue corals reproduce sexually by brooding. Instead of releasing eggs and sperm into the water where the fertilised egg develops into larvae, like many corals do, the larvae of blue corals develop inside the polyps. Each polyp produces one or two larvae, which subsequently attach themselves onto the colony before release. This may allow the larvae to develop further, and thus when the mature larvae are released into the water column it is able to settle in quickly. This means that the larvae will settle in a habitat that is already proven to be suitable for adult growth and reproduction. The larvae of blue coral have not been observed to swim, and thus dispersal of this coral is determined by water movement (5).
Conservation
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Blue corals are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that trade in this species should be carefully regulated (1). Blue corals will form part of the marine community in many marine protected areas (MPAs), which offer coral reefs a degree of protection, and there are many calls from non-governmental organisations for larger MPAs to ensure the persistence of these unique and fascinating ecosystems (6).
Description
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This unique species is the sole member of the order Helioporacea. Blue corals are thus named for their distinctive, permanently blue skeleton, which is generally hidden by greenish-grey or blue polyps (2). The coral polyp is basically an anemone-like animal that secretes a skeleton, at the base of which it is joined to other polyps to form a colony. The polyps of the blue coral each have eight tentacles (2), and the colonies form branching, plate-like or columnar colonies (3).
Habitat
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Blue corals occur in tropical waters, on intertidal reef flats and upper reef slopes (3).
Range
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Occurs in the Indo-Western Pacific, generally between 25°N and 25°S, where it is relatively uncommon (4).
Status
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Listed on Appendix II of CITES (1).
Threats
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Blue corals face the many threats that are impacting coral reefs globally. It is estimated that 20 percent of the world's coral reefs have already been effectively destroyed and show no immediate prospects of recovery, and 24 percent of the world's reefs are under imminent risk of collapse due to human pressures. These human impacts include poor land management practices that are releasing more sediment, nutrients and pollutants into the oceans and stressing the fragile reef ecosystem. Over fishing has 'knock-on' effects that results in the increase of macro-algae that can out-compete and smother corals, and fishing using destructive methods physically devastates the reef. A further potential threat is the increase of coral bleaching events, as a result of global climate change (6). Blue corals may also be threatened by over-harvesting for the coral trade, where it was one of the top ten genera of corals traded between 1985 and 1997 (7). It occurs primarily in the dead coral trade, as its beautiful skeleton makes it an attractive material for ornaments and jewellery, but they are also sometimes traded live for use in aquariums, where they do not usually survive more than a year (7).
Blue coral
provided by wikipedia EN
Blue coral (Heliopora coerulea) is a species of colonial coral. It is the only octocoral known to produce a massive skeleton.[3] This skeleton is formed of aragonite, similar to that of scleractinia. Individual polyps 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 octocoral with a massive skeleton,[3] which is composed of fibrocrystalline aragonite (calcium carbonate). It is a hermatypic zooxanthellaete 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.[4][5] It is a tolerant species and is used in marine aquariums.
Iron salts give the skeleton of Heliopora coerulea its unique color, which allows for easy recognition in fossil outcrops.[6] As such, it is fairly abundant within paleontology, with fossils indicating the species has remained unchanged since the Cretaceous.[6]
Blue coral has shown a particular resistance to thermal changes in their environments and have actually grown more in warmer temperatures.[7]
Close-up on live polyps (notice the 8 arms)
Preserved skeleton, showing the typical color
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 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, the acidification of oceans, and climate change.[1] 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. Its largest colony is believed to be located off Ishigaki Island in the Yaeyama Islands, 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.[1] The blue coral is listed under Appendix II of CITES.[1]
The world's largest deposit of blue coral is in Shiraho, Japan.[8] This deposit however was threatened by the possible development of an airport in 1989.[8] 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.[8] 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.[8]
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.[8] 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.[8] 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.[8]
Taxonomy
Heliopora coerulea was described by Pallas in 1766.[9]
References
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^ a b c d Obura, D.; Fenner, D.; Hoeksema, B.; Devantier, L.; Sheppard, C. (2008). "Heliopora coerulea". IUCN Red List of Threatened Species. 2008: e.T133193A3624060. doi:10.2305/IUCN.UK.2008.RLTS.T133193A3624060.en. Retrieved 19 November 2021.
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^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
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^ a b Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. p. 169. ISBN 0-03-056747-5.
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^ "Heliopora coerulea". Arkive.org. Archived from the original on 2015-09-05. Retrieved 17 August 2015.
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^ Leon P. Zann; Lesley Bolton (September 1985). "The distribution, abundance and ecology of the blue coral Heliopora coerulea (Pallas) in the Pacific". Coral Reefs. 4 (2): 125–134. doi:10.1007/BF00300871. S2CID 64814.
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^ a b Gornitz, V (2009). Encyclopedia of Paleoclimatology and Ancient Environments. Springer. pp. 202–203. ISBN 978-1402045516.
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^ Guzman, Christine; Atrigenio, Michael; Shinzato, Chuya; Aliño, Porfirio; Conaco, Cecilia (2019-09-27). "Warm seawater temperature promotes substrate colonization by the blue coral, Heliopora coerulea". PeerJ. 7: e7785. doi:10.7717/peerj.7785. ISSN 2167-8359. PMC 6768060. PMID 31579631.
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^ a b c d e f g Claus, C. A. 2020. Drawing the Sea Near: Satoumi and Coral Reef Conservation in Okinawa. Minneapolis: University of Minnesota Press
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^ "Heliopora coerulea". World Register of Marine Species. Retrieved 17 August 2015.
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Blue coral: Brief Summary
provided by wikipedia EN
Blue coral (Heliopora coerulea) is a species of colonial coral. It is the only octocoral known to produce a massive skeleton. This skeleton is formed of aragonite, similar to that of scleractinia. Individual polyps live in tubes within the skeleton and are connected by a thin layer of tissue over the outside of the skeleton.
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Biology
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zooxanthellate
van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO).
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Description
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Blue coral. This is not a true coral, but produces a limestone skeleton. Its skeleton is bright blue when cleaned. Its growth form is a series of vertical keels or branches, slender in very calm water, stout in more turbulent areas. When living, it looks brown, because of the covering of living tissue. Polyps are minute, usually giving a slightly furry appearance. Distribution: species extends across most of the Indian Ocean. (Sheppard, 1998 )
Roux, J.P. (2001) Conspectus of Southern African Pteridophyta. Southern African Botanical Diversity Network Report 13 Page 118 (Includes a picture).
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Habitat
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shallow water
van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO).
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