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Acropora cervicornis is noted for its rapid growth which can be between 10 and 20cm a year. This rapid growth is helped by the light structure of skeleton and allows it outgrow other coral species that may be living around it.
Acropora cervicornis is able to reproduce asexually though a process called fragmentation. When a piece of Acropora cervicornis breaks off from a colony it is able to form new branches that are genetically identical to the original colony. Although fragmentation allows Acropora cervicornis to recover quickly after damage it does mean the genetic diversity of the population is low which could have serious consequences when the population is infected with disease.
Sexual reproduction occurs by synchronous broadcast spawning. Acropora cervicornis is a hermaphrodite which means polyps have both male and female sex organs. Eggs take around ten months to develop, taking more time than the sperm but both mature at the same time. Once a year these eggs and sperm will be released simultaneously from all colonies at the same time. Spawning usually occurs at some point during July, August or September after a full moon and Acropora cervicornis can release between 600 to 800 eggs per cm2 of tissue! Once the eggs have been fertilised they will develop into planulae which are carried by water currents until they settle in suitable place to develop into a polyp. Despite the large numbers of eggs produced by Acropora cervicornis sexual reproduction is relatively unsuccessful.
As a zooxanthellate coral Acropora cervicornis is able to receive energy from a symbiotic relationship with single celled algae called Zooxanthellae. These zooxanthellae require sunlight in order to carry out photosynthesis which provides the coral with energy and so Acropora cervicornis is limited to depths at which sunlight is available. Acropora cervicornis is also able to feed itself by catching prey with its tentacles that contain stinging cells called nematocysts.
Acropora cervicornis is found on upper to mid reef slopes with a moderate to low wave exposure and in lagoons with clear water between depths of 1-25m
Coral disease such as White Band Disease (WBD) has caused massive declines in the population of Acropora cervicornis. During a survey of in Florida, USA, 72% of tagged colonies were affected by WBD and White Band Type II disease and of these 28% died. White Band disease reveals itself as a white band of skeleton and a rapid loss of tissue. The cause has not yet been isolated but may be due to a bacterium.
Coral bleaching is also a threat to Acropora cervicornis. In response to stressful conditions such as extreme, often high temperatures, pollution and sedimentation coral may expel its symbiotic zooxanthellae leaving a white, bleached appearance. When bleaching is prolonged it can lead to death and there is concern that as global temperatures continue to rise thermal induced bleaching will become a more common event and cause a greater loss of coral.
Acropora cervicornis is particularly vulnerable to storm damage due its delicate structure and subsequently hurricanes and tropical storms are a threat to this species. 2005 saw an unprecedented year for storm activity with 27 hurricanes and tropical storms recorded in the Atlantic. If this event were to be repeated annually it would cause extensive damage to coral reefs and they would have less time to recover between storms.
Ocean acidification is the changing pH of ocean water due to increased uptake of carbon dioxide from the atmosphere. Levels of atmospheric carbon dioxide are increasing and this will cause a further change in the pH of the ocean which impacts on organisms with calcium carbonate skeletons such as coral as it makes the skeleton brittle and slow to grow.
Over-fishing is a threat common to all regions of the world and affects all species of corals. The over-fishing of herbivorous fish can lead to an algae phase shift where algae become the dominant species on the reef because there are less fish eating the algae. An extensive phase shift was also seen during the 1980’s when there was a mass die off of the algae-eating sea urchin Diadema antillarum but once the Diadema population began to recover the coral cover did too.
Pollution and sedimentation are threats often associated with coastal communities and as coastal populations increase these threats are becoming greater. Sedimentation is the run-off in to water of sediment caused by poor land use or development and it affects corals by reducing light availability and smothering corals. Pollution lowers the water quality and together with sedimentation places stress on the corals which can make them more susceptible to bleaching and disease.
Acropora cervicornis is listed on CITES Appendix II which regulates the international trade of threatened species.
It is also listed on the Endangered Species Act 1973 (US) as Threatened.
There are no species specific conservation measures in place for Acropora cervicornis but region wide conservation in the Caribbean is being lead by the Caribbean Challenge, an ambitious pledge by 5 Caribbean nations (Bahamas, Jamaica, Grenada, the Dominican Republic and St. Vincent and the Grenadines) to protect 20% of their coastal marine areas by 2020. As a result of this pledge the Bahamas have so a far added 3.2 million acres of terrestrial and marine habitats to their network of MPAs.
Further research into the reproduction of Acropora cervicornis may help in the development of propagation techniques that would benefit the population.
An extension of Marine Protected Areas may also benefit this species but this would need to be accompanied by effective management to ensure the associated regulations are complied with.
The threat posed by ocean acidification could be addressed by taking action to reduce carbon emissions. International co-operation is required if carbon emissions are to be reduced but individuals could also contribute to the effort by adapting their own behaviour to reduce their carbon footprint.
Currently working on my PhD with a focus on EDGE coral species.
Acropora Biological Review Team. 2005. Atlantic Acropora Status Review Document. National Marine Fisheries Service, Southeast Regional Office.
Aronson, R., Bruckner, A., Moore, J., Precht, B. & E. Weil 2008. Acropora cervicornis. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. <www.iucnredlist.org>. Downloaded on 06 January 2011.
Fukami, H., Chen, C.A., Budd, A.F., Collins, A. Wallace, C. Et al. 2008. Mitochondrial and Nuclear Genes Suggest that Stony Corals are Monophyletic but Most Families of Stony Corals Are Not (Order Scleractinia, Class Anthozoa, Phylum Cnidaria). PLoS ONE 3(9):e3222. Doi:10.1371/journal.pone.0003222
Miller, M.W. et al. 2002. An analysis of the loss of acroporid corals at Looe Key, Florida, USA: 1983-2000. Coral Reefs. 21:179-182
NOAA Fisheries
http://www.nmfs.noaa.gov/pr/species/invertebrates/staghorncoral.htm
NOAA National Hurricane Centre: 2005 Atlantic Hurricane Season http://www.nhc.noaa.gov/2005atlan.shtml
Precht, W.F. and Aronson, R.B. (2006) Death and Resurrection of Caribbean coral reefs. Coral Reef Conservation p40-73. Cambridge University Press, Cambridge
Secretariat of the Convention on Biological Diversity (2009). Scientific Synthesis of the Impacts of Ocean Acidification on Marine Biodiversity. Montreal, Technical Series No. 46, 61 pages.
Veron J.E.N. 2000. Corals of the World. Volume 1. Townsville. Australian Institute of Marine Science.
Veron, J.E.N. et al. 2009. The coral reef crises: The critical importance of <350 ppm CO2. Mar Pollut Bull. 58:1428-1436
Wilkinson, C. (2008) Status of coral reefs of the world:2008. Global Coral Reef Monitoring Network and Reef and Rainforest Research Centre, Townsville, Australia.
Distribution map based on data provided by the IUCN Spatial Data Collection.
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