Abstract
With the increase in sea surface temperature (SST), scleractinian corals are exposed to bleaching threats but may possess certain flexibilities in terms of their associations with symbiotic algae. Previous studies have shown a close symbiosis between coral the and Symbiodinium; however, the spatial variation of the symbiosis and the attribution underlying are not well understood. In the present study, we examined coral-algal symbiosis in Galaxea fascicularis and Montipora spp. from three biogeographic regions across ~10° of latitude in the South China Sea. Analysis of similarities (ANOSIM) indicated a highly flexible coral-algal symbiosis in both G. fascicularis and Montipora spp. and canonical correspondence analysis (CCA) showed that temperature explained 83.2% and 60.1% of the explanatory subclade variations in G. fascicularis and Montipora spp., respectively, which suggested that temperature was the main environmental factor contributing to the diversity of Symbiodinium across the three regions. The geographic specificity of the Symbiodinium phylogeny was identified, revealing possible environmental selection across the three regions. These results suggest that scleractinian corals may have the ability to regulate Symbiodinium community structures under different temperatures and thus be able to adapt to gradual climate change.
Highlights
With the increase in sea surface temperature (SST), scleractinian corals are exposed to bleaching threats but may possess certain flexibilities in terms of their associations with symbiotic algae
The dataset included a total of 58 samples: six samples of G. fascicularis from Crescent Bay (CB)(Hong Kong), LHT(Sanya), Sunny Bay (SB)(Sanya) and Drummond Island (DI)(Sansha) each (CB_GA1-6, LHT_GA1-6, SB_GA1-6, DI_GA1-6), six samples of Montipora spp. from Lamma Island (LI)(Hong Kong) and SB(Sanya) each (LI_MO1-6, SB_MO1-6), four samples of Montipora sp. (LHT_MO1-4), two Montipora sp. technical replicates (LHT_MO5-6) from LHT(Sanya), five samples of Montipora sp. (CB_MO1-5), a Montipora sp. (CB_MO6) technical replicate from CB(Hong Kong) and two samples of seawater from each sampling site (CB_SW1-2, LI_SW1-2, LHT_SW1-2, SB_SW1-2, DI_SW1-2)
131 Symbiodinium subclades were assigned based on alignment to the ITS2 database according to 97% similarity, and 13 dominant subclades were selected for further analyses according to the relative abundance of the Symbiodinium subclade, the rest were regarded as “Others”
Summary
With the increase in sea surface temperature (SST), scleractinian corals are exposed to bleaching threats but may possess certain flexibilities in terms of their associations with symbiotic algae. The geographic specificity of the Symbiodinium phylogeny was identified, revealing possible environmental selection across the three regions These results suggest that scleractinian corals may have the ability to regulate Symbiodinium community structures under different temperatures and be able to adapt to gradual climate change. An understanding of coral-algal symbiosis change in response to different environmental conditions is essential to develop coral reef conservation strategies under future climate change. Because corals are able to change their Symbiodinium communities in response to diverse environmental stressors, for example, by gaining heat-tolerant Symbiodinium in an environment with an elevated temperature, the newly formed coral-algal symbiosis has been hypothesized to be more beneficial for coral survival[9]. After recovering from bleaching or remaining a sufficient duration in a relatively warm temperature, the coral host can gain some heat-tolerant Symbiodinium[9]. Sanya and Sansha, lying in the southern region of Hainan www.nature.com/scientificreports/
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