Diversity of Symbiodiniaceae in 15 Coral Species From the Southern South China Sea: Potential Relationship With Coral Thermal Adaptability

Abstract

It is well-known that the adaptability of coral-Symbiodiniaceae symbiosis to thermal stress varies among coral species, but the cause and/or mechanism behind it are not well-understood. In this study, we aimed to explore this issue based on zooxanthellae density (ZD) and Symbiodiniaceae genus/subclade. Hemocytometry and next-generation sequencing of the internal transcribed spacer region 2 (ITS2) marker gene were used to observe ZDs and Symbiodiniaceae genera/subclades associated with 15 typical coral species in the southern South China Sea (SCS). Average ZDs of all corals were in low levels, ranging from 0.84 to 1.22 × 106 cells cm−2, with a total of five Symbiodiniaceae genera, Symbiodinium, Cladocopium, Durusdinium, Fugacium, and Gerakladium, as well as 24 dominant subclades, were detected and varied among these coral species. Pocillopora verrucosa was dominated by Durusdinium (subclade D1/D1a), and other colonial corals were dominated by Cladocopium, but the subclades were varied among these species. Porites lutea and Montipora efflorescens were dominated by C15, and Echinopora lamellosa, Hydnophora exesa, and Coscinaraea exesa were dominated by C40. Acropora corymbosa, Merulina ampliata, and five species of Faviidae were mainly associated with Cladocopium types of C3u and Cspc. In contrast to other colonial corals, the dominant subclade of solitary Fungia fungites was C27, with high host specificity. Our study indicates that coral thermal stress adaptability is mainly affected by dominant Symbiodiniaceae type instead of ZD in the southern SCS. Some heat-sensitive corals, such as P. verrucosa corals, have acquired a high abundance of heat-tolerant Durusdinium to adapt to thermal stress. This could be the main reason for these corals becoming the dominant corals in this reef region. Background subclades analyses showed significant differences among coral species in subclade quantity and diversity. These suggest that numbers of coral species may have adapted to high environmental temperature by adopting various symbionts and/or associating with heat-tolerant Symbiodiniaceae.

Endosymbiont diversity and community structure in Porites lutea from Southeast Asia are driven by a suite of environmental variables

“…Consistent with previous work in Southeast Asia (LaJeunesse et al 2010; Leveque et al 2019;Qin et al 2019), the top three most common types identified in host colonies from all three regions belonged to the genus Cladocopium (Table 1), though the specific composition differed between regions (Fig. 2 & SI Fig.…”

Symbiont shuffling across environmental gradients aligns with changes in carbon uptake and translocation in the reef-building coral Pocillopora acuta

“…The combination of increased respiratory rates in mangrove compared to the reef, corroborated by a decrease in enriched storage lipid bodies suggests that heterotrophy is likely an additional way of supplementing the energetic requirements of corals in inhospitable conditions (which require an increased energetic demand to sustain homeostasis and survival) (Palardy et al 2008). Such diversity in response presumably reflects diverse resource requirements of 504 different host-coral species (Suggett et al 2017), how they are able to meet their requirements via heterotrophic supplementation (Fox et al 2018), and potential co-evolution of host-506 Symbiodiniaceae associations (Qin et al 2019;Wright et al 2019).…”

Differential Symbiodiniaceae Association With Coral and Coral-Eroding Sponge in a Bleaching Impacted Marginal Coral Reef Environment

“…Durusdinium communities in corals from the Andaman Sea with high host specificity were attributed to higher turbidity and high nutrient concentrations in the reef (LaJeunesse et al, 2010b). In general, the studies have confirmed that the Durusdinium type D1a or D1-4 (Durusdinium trenchii) are more frequently associated with corals in thermally challenged marginal habitats (Cooper et al, 2009;LaJeunesse et al, 2010a;Stat et al, 2013;Oladi et al, 2019;Qin et al, 2019;Williams and Patterson, 2020). D. trenchii is often referred to as an opportunistic symbiont which makes their association heterologous (Smith et al, 2017;Matthews et al, 2018).…”

“…The coral Galaxea fascicularis from the South China Sea was found to be more resistant to thermal stress because of its association with Durusdinium D1a (Zhou et al, 2017). In another report, Pocillopora verrucosa associated with Durusdinium D1a was found to be more resistant to thermal stress than Pocillopora lutea associated with Cladocopium (Qin et al, 2019). Interestingly, a decadal study with higher temperature variability in the Kenyan reef found that Pavona and Pocillopora were resistant to bleaching due to their association with Durusdinium (McClanahan et al, 2015).…”