Blue crust coral (Porites branneri)

Description

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Blue crust coral fact file

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

Blue crust coral description

Forming encrustations that vary in thickness and may measure up to 15 centimetres in diameter, colonies of the blue crust coral are relatively small, and are distinguished by knobbly upward projections and uniformly shaped septa. This species is generally pale or bluish, although it may also appear in varying shades of purple or brown ^{(3) (4) (5)}.  

Like other colony-forming corals, colonies of the blue crust coral are composed of numerous small polyps. The polyps secrete a hard calcareous skeleton, called a ‘corallite’, which contributes to the formation of a coral reef over successive generations ^{(3) (6)}.

Blue crust coral biology

Like other reef-building corals, the blue crust coral has many microscopic, photosynthetic algae, called zooxanthellae, living within the polyp tissues. Both the coral and its zooxanthellae are sensitive to changes in water temperature and acidity, and any increase in the water temperature greater than one or two degrees above the normal average may stress the coral and cause ‘bleaching’, a phenomenon in which the coral expels it zooxanthellae and turns white ^{(3) (6)}.

The coral and the algae have a mutually beneficial relationship; the coral provides protection for the algae, which in return provide energy and nutrients for the coral through photosynthesis ^{(3) (6)}. The blue crust coral is also able to supplement its diet with minute zooplankton, which it catches using stinging cells on tentacles which extend from the coral polyp ⁽³⁾.

Porites corals have separate male and female colonies. Instead of releasing bundles of eggs into the water, most Porites species brood the larvae inside their body cavity. Fertilisation is generally internal and therefore depends on free-swimming sperm from male colonies reaching the polyps of female colonies ⁽³⁾. When released, the larvae settle quickly, close to the parent colony. Whilst this means that, unlike spawning corals, the coral is not easily dispersed, brooding corals have the advantage of their young settling in an environment that has already proved suitable for successful reproduction ⁽⁶⁾.

Blue crust coral range

The blue crust coral is found in the southern Caribbean, including Jamaica and the Cayman Islands. It is also distributed along the north coast of South America, from Colombia to Venezuela, and in Trinidad and Tobago. In addition, the blue crust coral is known to inhabit part of the Brazilian coast, and has been recorded from the Fernando de Noronha Archipelago, Trindade Island, and Atol das Rocas ⁽¹⁾.

Blue crust coral habitat

A shallow water species, the blue crust coraltypically inhabits protected reef environments, as well as areas of hard ground, channels and intertidal pools, at depths of up to three metres ^{(1) (3)}. It has occasionally been recorded up to depths of 12 metres, where it may inhabit dead areas of older reefs ⁽⁵⁾.

The blue crust coral is commonly recorded in association with the coral Acropora palmate in the southern Caribbean ⁽¹⁾.

Blue crust coral status

The blue crust coral is classified as Near Threatened (NT) on the IUCN Red List ⁽¹⁾ and on Appendix II of CITES ⁽²⁾.

Blue crust coral threats

The blue crust coral shares many of the same threats that are faced by coral species around the world, including several specific threats to shallow water corals, such as pollution and sedimentation. Although less susceptible to bleaching than many coral genera, the Porites genus has proven to be more prone to the emerging threat of disease, which is causing widespread reef deterioration worldwide ⁽¹⁾.

However, the major threat to all corals is global climate change, which is expected to cause rising sea surface temperatures and ocean acidification, and more frequent, severe storms, which can damage reefs. Climate change will also increase the risk, frequency and duration of coral bleaching, even for the more hardy genera such as Porites, and will make corals more susceptible to disease, parasites and predators, such as the crown of thorns starfish (Acanthaster planci) ^{(1) (7) (8) (9)}.

Worldwide, there is also increasing pressure on coastal resources resulting from accelerating human population growth and development. There has been a significant increase in domestic and agricultural waste in the oceans, leading to pollution and sedimentation. The effects of the over-exploitation of reef resources, over-fishing and destructive fishing practices have also had damaging knock-on effects on many coral reefs ^{(7) (10)}. Porites species are also heavily collected for the aquarium trade ⁽¹⁾.

Blue crust coral conservation

The blue crust coral is listed on Appendix II of CITES ⁽²⁾, meaning that all trade in this species should be carefully monitored. Parts of this species’ distribution fall within Marine Protected Areas ⁽¹⁾.  

Recommended conservation measures for the blue crust coral include research on its population trends, abundance, ecology and habitat. There is a need to identify how resilient this species is to existing threats, and to identify any unknown threats it may face currently and in the future. Protected areas are likely to be beneficial to this species and so should be effectively managed and expanded, and potential new sites for protected areas should also be identified ^{(1) (7)}.

The blue crust coral is targeted by collectors for the aquarium trade. Population surveys should be carried out to monitor the effects of harvesting on this species, and fisheries management needs to be carefully considered, including setting catch quotas, size limits and no-take zones, especially within Marine Protected Areas ⁽¹⁾.

Find out more

Further information on the conservation of coral reefs:

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

Authentication

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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.

Calcareous

Containing free calcium carbonate, chalky.

Colonies

A group of organisms living together. Individuals in the group are not physiologically connected and may not be related, such as a colony of birds. Another meaning refers to organisms, such as bryozoans, which are composed of numerous genetically identical modules (also referred to as zooids or ‘individuals’), which are produced by budding and remain physiologically connected.

Fertilisation

The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.

Genus

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.

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.

Photosynthetic

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.

Polyp

Typically sedentary soft-bodied component of cnidaria, a group of simple aquatic animals including the sea anemones, corals and jellyfish. A polyp comprises a trunk that is fixed at the base, and a mouth that is placed at the opposite end of the trunk and is surrounded by tentacles.

Septa

In a coral, radial elements that project inwards from the corallite wall (the skeletal wall of an individual coral polyp).

Spawning

The production or depositing of large quantities of eggs in water.

Zooplankton

Tiny aquatic animals that drift with currents or swim weakly in water.

References

1. IUCN Red List (May, 2011)
   http://www.iucnredlist.org/
2. CITES (May, 2011)
   http://www.cites.org/
3. Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townville, Australia.
4. Coralpedia - Porites branneri (May, 2011)
   http://coralpedia.bio.warwick.ac.uk/en/corals/porites_branneri.html
5. Marine Species Identification Portal - Porites branneri (May, 2011)
   http://species-identification.org/species.php?species_group=caribbean_diving_guide&id=328
6. Veron, J.E.N. (1986) Corals of Australia and the Indo-Pacific. Angus and Robertson Publishers, UK.
7. Wilkinson, C. (2008) Status of Coral Reefs of the World: 2008. Global Coral Reef Monitoring Network Reef and Rainforest Research Centre, Townsville, Australia. Available at:
   http://www.icriforum.org/sites/default/files/Status%20Coral%20%20Reefs%20of%20World%202008%20%20Executive%20Summary_0.pdf
8. Carpenter, K.E. et al. (2008) One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science, 321: 560-563.
9. Miththapala, S. (2008) Coral Reefs. Coastal Ecosystems Series (Volume 1). Ecosystems and Livelihoods Group Asia, IUCN, Colombo, Sri Lanka.
10. Leão, Z.M.A.N., Kikuchi, R.K.P. and Olivera, M.D.M. (2010) Status of Eastern Brazilian coral reefs in time of climate changes. Pan-American Journal of Aquatic Sciences, 5(2): 224-235.