Coral reefs which form some of the most diverse ecosystems on Earth support many symbiotic relationships. Symbiodinium can provide up to 90% of a coral.s energy requirements. Temperature rise, turbid water and high salinity in the Persian Gulf were among the factors separating zooxanthellae from corals and result in bleaching phenomenon. Therefore, it is crucial to identify Symbiodinium of the Persian Gulf corals. Since zooxanthellae identification according to morphological characteristics is not precise enough, today, Symbiodinium different clades are identified using molecular techniques. In this study, Symbiodinium of genus Acropora as a dominant scleractinian coral in Farur Island, northern Persian Gulf were identified using molecular techniques. For this reason, sampling from depth of 7-10 meters was carried out. After DNA extraction, the target gene which was large subunit ribosomal RNA (28S rDNA) gene was amplified, using Polymerase Chain Reaction (PCR). Then the amplified fragments analyzed, by sequencing, and Symbiodinium clade was identified, using phylogenetic tree, and the situation of considered clade and its phylogenetic association with other studied samples in Iran and other parts of the world were defined. The
results showed that clade D was the only symbiont of Acropora off Farur Island. Since clade D is the most resistant clade against environmental changes, it is natural to identify this clade from Symbiodinium in Persian Gulf specific conditions.