Community composition of Symbiodiniaceae among four scleractinian corals in the eastern Gulf of Thailand

Abstract

Symbiotic algae in the family Symbiodiniaceae are essential for scleractinian corals’ survival and resilience. Understanding the community composition of Symbiodiniaceae species within coral colonies can provide insight into how corals respond to environmental changes. We examined Symbiodiniaceae community composition in four scleractinian coral hosts, Porites lutea, Platygyra daedalea, Pavona decussata and Pocillopora damicornis at six sites (n = 3-5 colonies/species/site) in the eastern Gulf of Thailand using Denaturing Gradient Gel Electrophoresis (DGGE) to resolve polymorphisms of the Internal Transcribed Spacer-2 (ITS2) DNA. The results showed that the Symbiodiniaceae genus Durusdinium was the most common clade in all coral hosts in all areas, whereas Cladocopium was common in P. lutea. We observed at least five prevalent Symbiodiniaceae species: Cladocopium goreaui (C1); two Cladocopium spp. (C3u and C15, C15v1); and at least two Durusdinium spp. (D1), which include Durusdinium sp. (D1-6 in P. damicornis), and at least one other Durusdinium sp. (D1) in all host coral species. Cladocopium sp. (C15) was highly abundant in P. lutea. Durusdinium spp. (D1) were the dominant species in P. decussata, P. daedalea and P. damicornis. PERMANOVA revealed the effects of site, host coral species and interaction between site and host coral species on the variation of Symbiodiniaceae species composition. Cluster analysis based on Bray–Curtis similarity index suggested four large groups. The first group, consisting of all coral host species (mainly P. daedalea, P. decussata and P. damicornis), had Durusdinium spp. (D1) as dominant species; the second group, consisting of P. lutea, had Cladocopium sp. (C15) as the dominant species; the third group, consisting of P. damicornis had D. glynnii (D1-6) as the dominant species; and the last group, consisting of P. daedalea had Cladocopium sp. (C3u) as the dominant species. Our results suggested complex interactions among Symbiodiniaceae species composition, coral species and environmental conditions.