Variation of symbiodiniaceae in broadcaster acropora humilis and brooder pocillopora damicornis corals

Abstract

Reef-building corals sustain a symbiotic relationship with single-cell algae belonging to family Symbiodiniaceae. Symbiotic algae contribute up to 50-95% of the metabolic needs by supplying photosynthetic products to the coral host. Therefore, the symbiosis between corals and Symbiodiniaceae is essential for the development and survival of coral reefs. Over the past years, significant losses and changes in coral reef ecosystems have been caused by anthropogenic activities and natural phenomena. Thus, relevant national organizations have raised awareness regarding the conservation of coral populations. Our Reef Biology Research Group, Department of Marine Science, Chulalongkorn University have been producing corals using a sexual propagation technique for coral reef rehabilitation since 2003. Nevertheless, studies on coral background, including their biology and adaptation mechanism, are required for policy and/or action plan of coral reef management and conservation. This study consisted of three experiments that aimed to collect the related information on corals, especially coral spawning, and investigate the diversity of Symbiodiniaceae in corals from the upper GoT. Two Acropora species spawn their gametes around 8 PM to 9 PM across all lunar periods with no clear indication of lunar-associated cue. According to year data, asynchronous spawning occurs and may lead to the low success of fertilization and the decreased number of coral recruitments (Experiment 1). A. humilis and P. damicornis exhibited the shuffling and switching of Symbiodiniaceae community under hatchery conditions. However, we recorded the association of Symbiodiniaceae genus Symbiodininium with coral, which has never been reported before in Thailand (Experiment 2). Tagged colonies of wild Acropora and Pocillopora corals showed a significant decline in zooxanthellae cells during summer, but the community of Symbiodiniaceae exhibited no change throughout the year (Experiment 3). The results from this study are useful for understanding the coral life cycle and coral-Symbiodiniaceae relationship, which can be applied to the prediction of potential adaptation of corals in localized reef environments and improve coral cultivation and conservation in Thailand.