Blue rice coral (Montipora flabellata)

Blue rice coral in shallow reef
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Blue rice coral fact file

Blue rice coral description

GenusMontipora (1)

Montipora flabellata is an encrusting coral which (3), upon close inspection, does indeed resemble blue rice. Known as a scleractinian, or stony, coral due to its hard skeleton (4), this attractive species is normally a flat, ground-covering coral, but an unusual branching form also exists in the waters off a single island, due to a remarkable symbiotic relationship with a small shrimp (3).


Blue rice coral biology

Montipora flabellate, like many corals, has a special, mutually beneficial relationship with photosynthetic algae known as zooxanthellae, which lives within the coral’s tissues. The coral provides protection for the algae and in return the algae provide energy and nutrients for the coral, produced through photosynthesis (5). As the algae require light to photosynthesize, Montipora flabellate is restricted to relatively shallow waters where sunlight can penetrate (3). Recent research has shown that Montipora flabellata also has another organism living within its tissues – a nitrogen-fixing bacterium that is thought to provide both the zooxanthellae and the coral with nitrogen (6).

The branching form of Montipora flabellate is the result of a relationship with another organism: a shrimp from the genus Gammaropsis. The Gammaropsis shrimp forms a tube to live in which the coral skeleton covers as it grows. This results in a hollow tube running up the centre of each branch of coral, with an opening at the tip through which the shrimp can enter. The shrimp benefits from protection from the coral skeleton, whilst Montipora flabellata is able to form a branched colony that enables it to compete for space with other branched corals (3).

Montipora flabellata is a hermaphrodite; that is, each individual has both male and female sexual organs. Spawning, when a mass of eggs and sperm are released into the surrounding water, occurs between July and September between 21:00 and 22:00 hours. The incredibly precise synchronised release of eggs and sperm increases the chances of reproductive success (4). Fertilisation occurs on the surface and the resulting coral larvae then actively select substrate to settle on (4). As well as this sexual reproduction, Montipora species are also known to reproduce asexually by fragmentation (1). Reef-building corals such as this species do not reach maturity until three to eight years and their lifespan is unknown (1).


Blue rice coral range

Montipora flabellata is endemic to Hawaii, where it is found on all the islands apart from Johnston atoll (1).  


Blue rice coral habitat

This species of coral is found in shallow, high wave-energy environments down to a depth of ten metres.  It occurs on both flat and sloped reefs (1).


Blue rice coral status

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (2).

IUCN Red List species status – Vulnerable


Blue rice coral threats

With around one third of the world’s reef-building corals facing extinction (7), it is unsurprising that the blue rice coral is considered Vulnerable (1). One of the main risks to Montipora flabellata is an increased risk of mass coral bleaching episodes as a result of climate change (8). When sea temperatures rise over 27 degrees Celsius (3), corals become stressed and expel the zooxanthellae. For example, in 2002 and 2004 the north-western Hawaiian Islands suffered from bleaching episodes, resulting in almost 100 percent of Montipora flabellata colonies expelling their zooxanthellae (8). If the sea temperature rises are brief events coral may recover, but if they are prolonged coral tissue dies and only the white, limestone skeleton remains. Increased sea temperatures also affect corals by increasing their susceptibility to diseases and the numbers of diseases present (1). One study showed nearly 30 percent of reefs in Hawaii have Montipora-specific diseases, such as Montipora white syndrome which causes acute tissue loss (9).

Invasive species of algae have been reported in Hawaii and may cause problems by carpeting the coral, preventing light from reaching the zooxanthellae, thus inhibiting the algae’s ability to photosynthesise and produce energy. Sedimentation has a similar affect on the zooxanthellae (3), and also adversely affects dispersal of eggs and sperm during spawning, and hinders the settlement and development of the larvae (4). Sedimentation, caused by soil erosion following deforestation and intensive plantation agriculture (4), is no small problem; an estimated 1.9 million tons of soil enter the ocean each year from the island of Kaho’olawe alone (10).

Montipora flabellata may also be threatened by the crown of thorns starfish (Acanthaster planci), a voracious predator of reef-building corals in the Pacific. It has been observed preferentially preying on Montipora species although it prefers branching rather than encrusting corals so may have limited effect on Montipora flabellata (1).

Finally, Montipora flabellate, like many corals worldwide, is threatened by dynamite fishing, cyanide fishing (1), dredging for coastal construction (3) and pressures from tourism and recreation. Climate change can alter the native species dynamics, cause ocean acidification (1) and cause an increase in tropical storms and hurricanes. Volcanic eruptions may adversely affect Montipora flabellata if it reacts in a similar way to Montipora verrucosa which takes ten years to re-colonise a reef after a lava flow (11).


Blue rice coral conservation

The Hawaiian Department of Land and Natural Resources has established ten Marine Life Conservation Districts (MLCDs) as part of the United States national Marine Protected Areas network. The first MLCD was established in 1967 in Hanauma Bay on Oahu Island and fishing here is now restricted, benefitting the reefs by reducing damage from fishing practices (12). The resultant increase in the numbers of herbivorous fish also helps by limiting the spread of invasive algae (10). Harvesting of coral for aquarium specimens and destructive practices such as dredging are also banned (12).

All corals are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES). Species in Appendix II are not necessarily threatened with extinction but trade in these species could result in this. Export licences are required to trade in these species, so that their survival is not detrimentally affected by trade (2).

In the future, the conservation of coral biodiversity may require the use of artificial propagation and the freezing of gametes, which can be preserved in perpetuity and used to grow coral colonies to restore reefs in the wild (1).

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


This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:

This species information was authored as part of the Arkive and Universities Scheme.


Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
Of asexual reproduction: reproduction that does not involve the formation of sex cells (‘gametes’).
A coral colony is composed of numerous genetically identical individuals (also referred to as zooids or polyps), which are produced by budding and remain physiologically connected.
Encrusting corals have little upward growth and instead spread out low like a crust on rocky surfaces.
A species or taxonomic group that is only found in one particular country or geographic area.
The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.
A form of asexual reproduction where a new organism grows from a fragment of the parent. Each fragment develops into a mature, fully grown individual.
Reproductive cells which carry the genetic information from their parent, and are capable of fusing with a gamete of the opposite sex to produce a fertilized egg. In animals, male gametes are called sperm and female gametes are called ova.
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
Possessing both male and female sex organs.
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.
Capable of photosynthesis, a 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.
The surface a plant or animals lives upon.
Describes a relationship in which two organisms form a close association. The term is now usually used only for associations that benefit both organisms (a mutualism).


  1. IUCN Red List (March, 2010)
  2. CITES (March, 2010)
  3. Jokiel, P., Brown, E., Rodgers, K. and Smith, W. (2008) Reef corals and the coral reefs of south Moloka’i. In: Field, M.E., Cochran, S.A., Logan, J.B. and Storlazzi, C.D. (Eds.) The Coral Reef of South Moloka‘i, Hawai‘i: Portrait of a Sediment-Threatened Fringing Reef. U.S. Geological Survey, Scientific Investigations Report, 2007-5101.
  4. Kolinski, S. and Cox, E. (2003) An update on modes and timing of gamete and planula release in Hawaiian scleractinian corals with implications for conservation and management. Pacific Science, 57: 17-27.
  5. Thornhill, D. (2003) Diversity and community structure of Symbiodinium from Hawaiian coral reefs. Hawai’i Institute of Marine Biology Technical Report, 43: 89-99.
  6. Olson, N., Ainsworth, T., Gates, R. and Takabayashi, M. (2009) Diazotrophic bacteria associated with Hawaiian Montipora corals: Diversity and abundance in correlation with symbiotic dinoflagellates. Journal of Experimental Marine Biology and Ecology, 371: 140-146.
  7. Carpenter, K. et al. (2008) One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science, 321: 560-563.
  8. Kenyon, J. and Brainard, R. (2006) Second recorded episode of mass coral bleaching in the North-western Hawaiian Islands. Atoll Research Bulletin, 543, 505-523.
  9. Friedlander, A., Aeby, G., Brainard, R., Brown, E., Chaston, K., Clark, A., McGowan, P., Montgomery, T., Walsh, W., Williams, I. and Wiltse, W. (2008) The state of coral reef ecosystems of the Main Hawaiian Islands. In: Waddell, J. (Ed.) The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States. NOAA/NCCOS Center for Coastal Monitoring and Assessment’s Biogeography Team, Silver Spring, Maryland.   
  10. Kaho’olawe Island Reserve Commission (March, 2010)
  11. Grigg, R. and Maragos, J. (1974) Re-colonisation of hermatypic corals on submerged lava flows in Hawaii. Ecology, 55: 387-395.
  12. Marine Protected Areas of the United States (March, 2010).

Image credit

Blue rice coral in shallow reef  
Blue rice coral in shallow reef

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