Blue coral (Heliopora coerulea)

Description

Blue coral fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Blue coral description

A unique species, blue coral (Heliopora coerulea) 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 ⁽³⁾. 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 ⁽³⁾, and the colonies form branching, plate-like or columnar colonies ⁽⁴⁾.

Blue coral biology

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 ⁽⁴⁾. 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 ⁽⁶⁾.

Blue coral range

Blue coral occurs in the Indo-Western Pacific, generally between 25 degrees North and 25 degrees South, where it is relatively uncommon ⁽⁵⁾.

See this species on Google Earth.

Blue coral habitat

Blue corals occur in tropical waters, on intertidal reef flats and upper reef slopes ⁽⁴⁾.

Blue coral status

Blue coral is classified as Vulnerable (VU) on the IUCN Red List ⁽¹⁾, and is listed on Appendix II of CITES ⁽²⁾.

Blue coral threats

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 ⁽⁷⁾. 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 ⁽⁸⁾. 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 ⁽⁸⁾.

Blue coral conservation

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 ⁽²⁾. 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 ⁽⁷⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

For further information on blue coral:

• Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townsville, Australia.

For further information on the conservation of coral reefs see: 

• Reef Check:
  www.reefcheck.org
• The Coral Reef Alliance:
  www.coralreefalliance.org

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Glossary

Algae

Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.

Colony

Relating to corals: organisms, such as corals, which are composed of numerous genetically identical modules (also referred to as zooids, polyps or 'individuals'), which are produced by budding and remain physiologically connected.

Hermatypic

Reef-building corals. Most hermatypic corals have a close association with algae known as zooxanthellae, which live in their tissues. These corals are restricted to shallow, tropical, marine environments. Over time the accumulated deposition of calcium carbonate (limestone) by many hermatypic corals can form large limestone structures known as coral reefs.

Larvae

Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

Photosynthesis

Metabolic process characteristic of plants in which carbon dioxide is broken down, using energy from sunlight absorbed by the green pigment chlorophyll. Organic compounds are made and oxygen is given off as a by-product.

Polyp

Typically sedentary soft-bodied component of Cnidaria (corals, sea pens etc), which comprise of a trunk that is fixed at the base; the mouth is placed at the opposite end of the trunk, and is surrounded by tentacles.

Symbiotic

Describing a close relationship between two organisms. This term usually refers to a relationship that benefits both organisms.

References

1. IUCN Red List (April, 2011)
   http://www.iucnredlist.org/
2. CITES (July, 2007)
   http://www.cites.org
3. Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townsville, Australia.
4. Veron, J.E.N. (1986) Corals of Australia and the Indo-Pacific. Angus & Robertson Publishers, London, UK.
5. Zann, L.P. and Bolton, L. (2004) The distribution, abundance and ecology of the blue coral Heliopora coerulea (Pallas) in the Pacific. Coral Reefs, 4: 125 - 134.
6. Harii, S. and Kayanne, H. (2003) Larval dispersal, recruitment, and adult distribution of the brooding stony octocoral Helipora coerulea on Ishigaki Island, southwest Japan. Coral Reefs, 22: 188 - 196.
7. Wilkinson, C. (2004) Status of Coral Reefs of the World. Australian Institute of Marine Science, Townsville, Australia.
8. Green, E. and Shirley, F. (1999) The Global Trade in Corals. World Conservation Press, Cambridge, UK.