Acropora recruits harbor “rare” Symbiodinium in the environmental pool

• Published in: Coral reefs 2013-06, Vol.32 (2), p.355-366
• Main Authors: Yamashita, H., Suzuki, G., Hayashibara, T., Koike, K.
• Format: Article
• Language: English
• Subjects: Acropora; Algae; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; Coral reefs; Freshwater & Marine Ecology; Fundamental and applied biological sciences. Psychology; Life Sciences; Marine ecology; Oceanography; Protozoa; Sea water ecosystems; Spawning; Symbiodinium; Symbiosis; Synecology; Thermal stress; Water column
• ISSN: 0722-4028; 1432-0975
• DOI: 10.1007/s00338-012-0980-2

Coral–algal symbioses are essential for the survival of corals. Algal endosymbionts, specifically the dinoflagellate genus Symbiodinium , are divided into several genetic clades. The composition of Symbiodinium within corals plays an important role in the tolerance and/or sensitivity of host corals to local environments, due to individual Symbiodinium -specific physiological characteristics. While the majority of gamete-spawning corals acquire Symbiodinium from the surrounding environment, little is known about whether corals specifically select or randomly acquire Symbiodinium from the environmental population. In the present study, we compared the Symbiodinium clade composition of newly recruited Acropora corals with that of the environmental pool (water column, sediments, and adult colonies). More than 90 % of recruits harbored clades A and/or D until 6 months after settlement, despite the Symbiodinium environmental pool being mainly composed of clade C (mainly ITS1 type C2), and to a lesser extent clades A and D. In addition, the environmentally dominant type C2 Symbiodinium was not detected in Acropora recruits, while a few recruits harbored ITS1 types C1 or C15. Therefore, the clade composition of recruits may not reflect the abundance/density of Symbiodinium populations in the environment. Some members of clades A and D are known to exhibit tolerance to a wide range of environments. ITS1 type C1 also exhibits greater tolerance to thermal stress compared to ITS1 type C2. These tolerance characteristics of certain Symbiodinium may be vital for the initial survival of Acropora recruits, even if these Symbiodinium are rare in the environment.