Plesiastrea versipora is a zooxanthellate coral which means that it obtains some of its nutrition from single celled algae called zooxanthellae living in its tissue. These zooxanthellae require sunlight for photosynthesis so Plesiastrea versipora is largely restricted to habitats where there is light availability. However Plesiastrea versipora is not entirely dependent on zooxanthellae for nutrition as the tentacles of this species are able to catch plankton. The tips of the tentacles which are located around the edges of the corallite wall contain stinging cells (nematocysts) that stun plankton and allow the tentacles to take hold of the prey and pass it to the mouth of the corallite.
The growth form of a colony of Plesiastrea versipora can depend on the location and habitat in which it grows. Colonies at high latitudes grow larger than those found in the tropics and colonies in shallow, exposed areas are more rounded in shape compared to flatter, plate like colonies found in habitats where the light intensity is low. The ability of Plesiastrea versipora to grow even at cooler temperatures in high latitude is an ecological trait that distinguishes this species from many others.
Plesiastrea versipora is a broadcast spawning species which means it reproduces by releasing large numbers of eggs and sperm into the water column where they will become fertilised. Many species of coral are known to spawn synchronously at certain times of the year, often following a lunar cycle. The fertilised eggs develop into planulae and travel in the water column until they settle onto a suitable substrate and develop into a polyp. This polyp is then able to reproduce asexually through a process known as budding. Plesiastrea versipora grows though extratentacular budding where new polyps develop on the side of a parent polyp and pinch off to form a new polyp.
The population of Plesiastrea versipora is declining.
The percentage of live coral cover is decreasing across the world. 19% of the worlds corals reefs have already been effectively lost and this trend looks set to continue.
There are a number of threats to the population of Plesiastrea versipora. Ocean acidification is a result of the increasing levels of carbon emissions produced by human activities. Carbon dioxide (CO2) naturally dissolves in sea water but as carbon dioxide levels in the atmosphere continue to increase, more CO2 is dissolving into the water, disrupting the normal chemical balance and altering the pH of the water. This pH change affects the calcium carbonate skeletons of coral by making them more brittle and slower to grow. If CO2 levels in the atmosphere continue to increase the pH of the ocean will continue to decrease and if this change continues at the current rate then by 2040 the coral reefs of the world could be in an irreversible decline.
Human activities are threatening coral species such as Plesiastrea versipora in additional ways. The growing human population in all areas of the world is placing greater pressure on marine resources such as fish for food and the conversion of coastal habitats, such as mangroves, for residential and industrial use. Overfishing and the destructive techniques such as dynamite, poison and trawling cause direct physical damage to the reef and reduce the number of herbivorous fish that traditionally control the growth of algae. Without herbivorous fish a coral reef can quickly become dominated by algae in a process known as an algae phase shift that reduces light and oxygen availability and places stress on the coral.
Stress is also placed onto coral by sedimentation and pollution which are the results of habitat destruction and coastal development. As coastal areas are developed, sediment and pollution is washed onto the reef reducing light availability and water quality. Sediment, such as soil, can settle onto coral and smother it to death if the coral is unable to remove it. The stress caused by algae phase shifts, sedimentation and pollution also make corals more susceptible to diseases and bleaching.
Coral bleaching is the expulsion of symbiotic zooxanthellae from the tissue of the coral and is a response to stressful conditions such as temperature extremes or pollution. Thermally induced bleaching is occurring more frequently as sea temperatures increase as the global climate changes. Although it is not known how susceptible Plesiastrea versipora is to thermally induced coral bleaching, it is a threat that has to be taken seriously as the climate continues to change.
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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
Mora, C. et al. 2006. Coral Reefs and the Global Network of Marine Protected Areas. Ecology 312:1750-1751
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 2. 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 Center, Townsville, Australia.
Distribution map based on data provided by the IUCN Spatial Data Collection.
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