Comparison of Symbiodinium populations in corals from subtidal region and tidal pools of northern coasts of Hengam Island, Iran

Coral reefs are integral part of tropical ecosystems and obligatory symbiosis with the genus Symbiodinium has a vital role in resistance and survival of the holobiont. Nine different genetic clades (A to I) have been discovered by molecular techniques. Members of Symbiodinium are ecologically and biogeographically diverse and their distribution patterns are determined by temperature, irradiance, depth, season and latitude however stress-tolerant species might be detected within each clade. Samples of four coral species from subtidal region in the north of Hengam Island, Persian Gulf (PG) and its tidal pools were analyzed by internal transcribed spacer of ribosomal DNA and by the aid of Denaturing Gradient Gel Electrophoresis (DGGE) to compare the differences in populations of their symbionts. The results showed that some subtidal colonies of one species harbored less tolerant subtypes of Symbiodinium subclade C7. Nonetheless, clade D Symbiodinium was the most dominant symbiotic clade in both tidal pool and subtidal coral colonies. A novel subtype of subclade D1 Symbiodinium was also detected in some coral colonies and was inferred as subclade D1.PG Symbiodinium. The prevalence of clade D Symbiodinium might reflect corals response to extreme environmental stresses of tidal pools and the northern PG itself that coral inhabitants have to cope with.