Porites is a genus of stony coral; they are small polyp stony (SPS) corals. They are characterised by a finger-like morphology. Members of this genus have widely spaced calices, a well-developed wall reticulum and are bilaterally symmetrical. Porites, particularly Porites lutea, often form microatolls.[3] Corals of the genus Porites also often serve as hosts for Christmas tree worms (Spirobranchus giganteus).
Specimens of Porites are sometimes available for purchase in the aquarium trade. Due to the strict water quality, lighting and dietary requirements, keeping Porites in captivity is very difficult.
Most Porites that are collected have Christmas tree worms (Spirobranchus giganteus) that bore into the coral, serving as additional aesthetic livestock. These particular Porites specimens are called "christmas tree worm rocks" or "christmas tree worm coral".
Porites corals have been shown to be accurate and precise recorders of past marine surface conditions.[4] Measurements of the oxygen isotopic composition of the aragonitic skeleton of coral specimens indicate the sea-surface temperature conditions and the oxygen isotopic composition of the seawater at the time of growth.[5] The oxygen isotopic composition of seawater can indicate the precipitation/evaporation balance because oxygen atoms of the more abundant mass 16 will preferentially evaporate before the more rare mass 18 oxygen. The relationship between temperature, precipitation, and the oxygen isotopic composition of Porites corals is important for reconstructing past climates, and associated large-scale patterns such as the El-Nino Southern Oscillation, the Intertropical Convergence Zone, and the mean state of the climate system.
Corals in the genus Porites are found in reefs throughout the world. It is a dominant taxon on the Pandora platform of the Great Barrier Reef. Potts et al. (1985) identified 7 dominant species: P. lobata, P. solida, P. lutea, P. australiensis, P. mayeri, P. murrayensis, and P. anae. The oldest of six colonies in this reef was approximately 700 years old, and was estimated to be growing at 10.3 mm per year.[6]
Meyer and Schultz (1985) demonstrated that P. furcata has a mutualistic relationship with the schools of French and white grunts (Haemulon flavolineatum and H. plumierii) that rest in their heads during the day. The fish provide it with ammonium, nitrates, and phosphorus compounds. Coral heads with resting grunts experience significantly higher growth rates and nitrogen composition than those without.[7]
Representatives of this genus are found in both the Indo-Pacific and Caribbean basins.
Some species in this genus demonstrate high levels of halotolerance. In the Gulf of Thailand P. lutea tolerates daily tidal shifts of 10-30‰ salinity. Moberg et al. (1997) determined that when the salinity declines, the symbiotic zooxanthellae decrease their photosynthesis rate as the coral contracts its polyps to protect them. The corals maintain their metabolic rate by temporarily switching to heterotrophy, consuming prey such as brine shrimp and other zooplankton.[8]
Porites growth rates can be determined by examining annual rings in their skeleton. This method was used to determine that P. astreoides grows its skeleton about the central axis by approximately 3.67mm/year, calcifies at approximately 0.55g/cm²/year, and increases density in this region of the body at approximately 1.69g/cm³/year.[9] Additionally, Meyer and Schultz (1985) reported that coral growth varies seasonally. They observed that P. furcata's growth rate peaked between May and August, which is summertime in their Caribbean habitat.[10]
Threats to corals in the genus Porites include predation, climate change, and anthropogenic pollution. When exposed to increased temperatures and copper, P. cylindrica slowed its rate of production. Additionally, the symbiotic zooxanthellae reduced their photosynthesis rate when exposed to both stressors.[11]
Done and Potts (1992) observed that when settled, larvae in Porites are vulnerable to competition from other corals and predation from sea urchins. Additionally, mortality likelihood increases following strong storms.[12]
Porites is a genus of stony coral; they are small polyp stony (SPS) corals. They are characterised by a finger-like morphology. Members of this genus have widely spaced calices, a well-developed wall reticulum and are bilaterally symmetrical. Porites, particularly Porites lutea, often form microatolls. Corals of the genus Porites also often serve as hosts for Christmas tree worms (Spirobranchus giganteus).
Porites est le nom d'un genre de coraux massifs, souvent caractérisé par des digitations (forme évoquant des doigts).
Certains Porites forment des blocs extrêmement solides et compacts : ce sont des organismes dits « bioconstructeurs » qui participent à la construction des récifs biogènes.
On trouve les porites dans les eaux tropicales chaudes de la Mer Rouge, du bassin Indo-Pacifique tropical, des Caraïbes et de l’Atlantique tropical.
Ce sont généralement des coraux extrêmement compacts et solides, à croissance lente et à durée de vie longue. Ils sont considérés comme plus résistants aux prédateurs (poissons perroquets, étoiles de mer corallivores...) que les coraux à croissance rapide, et abritent souvent de nombreux symbiotes (vers tubicoles, bénitiers, huîtres corallicoles...). Ils constituent donc un élément à la fois central et fragile des écosystèmes coralliens.
En outre, la solidité de leur squelette fait qu'à leur mort, leur corps ne se désagrège pas mais forme un nouveau substrat dur sur lequel de nombreux autres organismes pourront élire domicile : ils constituent ainsi des briques essentielles à la formation d'un récif de corail, où ils font partie des principales espèces fondatrices.
Les colonies de porites peuvent être encroûtantes, aplaties (foliacées), ramifiées ou massives en forme de dôme. Les colonies en forme de dôme peuvent atteindre 8 m de hauteur et être âgées de près de 1000 ans.
La principale source de son alimentation vient de sa symbiose avec les zooxanthelles. La source secondaire de son alimentation, c'est, comme tous les cnidaires, le plancton qu'il attrape avec ses tentacules urticantes[1].
Selon World Register of Marine Species (31 janvier 2014)[2] : ...
Selon ITIS (31 janvier 2014)[3] :
Assemblage corallien sur l'atoll de Palmyra, avec plusieurs espèces de Porites.
Colonie d'âge vénérable à Mayotte.
Porites est le nom d'un genre de coraux massifs, souvent caractérisé par des digitations (forme évoquant des doigts).
Certains Porites forment des blocs extrêmement solides et compacts : ce sont des organismes dits « bioconstructeurs » qui participent à la construction des récifs biogènes.
_closeup.jpg)
