In intertidal reef-flat environments, massivePorites form characteristicmicroatoll formations, with living tissues around the perimeter, and dead skeleton on the exposed upper surface. Microatoll growth is predominantly lateral, as vertical growth is limited by a lack of accommodation space.[2]Small colony ofPorites porites
Specimens ofPorites are sometimes available for purchase in the aquarium trade. Due to the strict water quality, lighting and dietary requirements, keepingPorites in captivity is very difficult.
MostPorites that are collected haveChristmas tree worms (Spirobranchus giganteus) that bore into the coral, serving as additional aesthetic livestock. These particularPorites specimens are called "christmas tree worm rocks" or "christmas tree worm coral".[citation needed]
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 ofPorites 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 genusPorites are found in reefs throughout the world. It is a dominant taxon on the Pandora platform of theGreat Barrier Reef. Potts et al. (1985) identified 7 dominant species:P. lobata,P. solida,P. lutea,P. australiensis,P. mayeri,P. murrayensis, andP. 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 thatP. furcata has a mutualistic relationship with the schools of French and white grunts (Haemulon flavolineatum andH. 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 theIndo-Pacific andCaribbean basins.
Some species in this genus demonstrate high levels ofhalotolerance. In theGulf of ThailandP. 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 thatP. 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 thatP. furcata's growth rate peaked between May and August, which is summertime in their Caribbean habitat.[10]
Threats to corals in the genusPorites 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 inPorites are vulnerable to competition from other corals and predation from sea urchins. Additionally, mortality likelihood increases following strong storms.[12]
^Elizalde-Rendon, E.M.; Horta-Puga, G.; Gonzalez-Diaz, P.; Carricart-Ganivet, J.P. (2010). "Growth characteristics of the reef-building coral Porites astreoides under different environmental conditions in the Western Atlantic".Coral Reefs.29 (3):607–614.Bibcode:2010CorRe..29..607E.doi:10.1007/s00338-010-0604-7.S2CID20491507.
^Nystrom, M.; Nordemar, I.; Tedengren, M. (2001). "Simultaneous and sequential stress from increased temperature and copper on the metabolism of the hermatypic coral Porites cylindrica".Marine Biology.138 (6):1225–1231.doi:10.1007/s002270100549.S2CID85015152.
^Done, T.J.; Potts, D.C. (1992). "Influences of habitat and natural disturbances on contributions of massive Porites corals to reef communities".Marine Biology.114 (3):479–493.doi:10.1007/BF00350040.S2CID83505538.
