The Hermatypic Scleractinian (Hard) Coral Fauna of the Gulf

The harsh climate of the Gulf puts severe constraints on coral survival and, therewith, on biodiversity by restricting the number of coral species that can survive in the harsh conditions. Despite this and despite being at the western high-latitude edge of Indo-Pacific reef coral distribution, the Gulf’s coral fauna is surprisingly rich. Within the region, the richest Gulf coral fauna has been recorded from Saudi Arabia, around the islands of Jana and Karan (50 species, Basson et al. 1977). Fadlallah et al. (1993) subsequently recorded 23 and 19 species in specific sample sites on these two islands and suggested that species richness may actually be lower than suggested by Basson et al. (1977). This is also supported by data in Vogt (1996). The UAE presently has the second-richest documented coral fauna, with 34 scleractinian species (Riegl 1999). More comprehensive studies in other areas and the region would likely reveal a quite homogeneous fauna with little diversity gradient across the Gulf proper. The Iranian coral fauna is rich due to water circulation pattern and better environmental conditions in the northern Gulf. Due to counter clock wise pattern of the water circulation in the Gulf, the northern part and the Iranian coastline has lower temperature, lower salinity, better aragonite saturation, besides also greater depth (see Chap. 2). This results in increasing species richness towards the Straits of Hormuz. In general, coral diversity decreases from east to west and from north to south. This has been seen in octocorals (Samimi-Namin and van Ofwegen 2009) and the same trend exist for hard corals (Samimi-Namin, unpublished data). It is still unclear where the main species boundaries are located and therefore further studies are necessary to fully reveal coral diversity in the Gulf.