Disparate types of symbiotic algae occur within branching and massive corals of Chabahar Bay: An implication for different response of corals to environmental stress

However the Gulf of Oman is generally regarded as a favorable habitat for corals to occur, yet its monsoon-driven upwellings result in low water temperature and turbidity, which are considered as environmental stressors for corals. Chabahar Bay is one of the few regions of the Iranian coast of the Gulf of Oman which harbors stony corals. It has been suggested that stress tolerance in corals is linked to the type of unicellular algae (genus Symbiodinium) residing within their tissue. To date, no study has investigated the type of Symbiodinium in corals from the northern Gulf of Oman. Therefore, this study aims at characterizing Symbiodinium diversity in branching coral Acropora sp. and massive coral Favites sp. from Chabahar Bay. In doing so, 20 fragments of each coral were collected from southeastern Chabahar Bay in May 2016 by SCUBA diving and then were analyzed for genotyping using the ITS2 gene. According to our results, all Acropora samples harbored type D1a, whereas all Favites samples contained type C1. These two types of Symbiodinium are known to exhibit different stress tolerances. While type D1a is a stress tolerant endosymbiont which is common in stressed corals, type C1 is considered as thermally sensitive. However, unlike C1-Symbiodinium, type D1a can also be dominated in corals in turbid waters and only after bleaching. Our data demonstrate that acroporid corals of the Chabahar Bay seem to be in a more critical condition than the massive corals since there are fitness trade-offs associated with choosing clade D symbionts over other clades that don’t affect the long-term growth and survival of the coral.

Keywords:

Branching Coral , Massive Coral , Symbiodinium , Gulf of Oman , Chabahar Bay