Symbiodinium thermophilum symbionts in Porites harrisoni and Cyphastrea microphthalma in the northern Persian Gulf, Iran

Abstract

Coral communities of the Persian Gulf (PG) withstand maximum and annual ranges of water temperatures that surpass those found on the majority of reefs elsewhere. As such, these communities may inform on how coral reefs might adapt to the warmer waters of the future. Depending on the algal symbiont (genus Symbiodinium) harboured, advantages in stress tolerance may be conferred to the coral holobiont. Characterizing the algal component is therefore critical in determining the coral holobiont's tolerance phenotype. Coral associations off the Arabian coastline of the PG have been characterized as biogeographically unique, containing a rare group of taxonomically ancestral and thermotolerant algal symbionts, the Symbiodinium thermophilum group. In contrast, waters off the Iranian coast remain poorly characterized with a notable lack of S. thermophilum group symbionts identified in coral associations to date. Here, we characterize the algal component of two reef building corals (Porites harrisoni and Cyphastrea microphthalma) predominant at three sites spanning almost the entire length of the PG's Iranian coast. Genotyping using the chloroplastic 23S and nuclear ITS2 genes, we demonstrate the presence of S. thermophilum group symbionts. We discuss the probable physical drivers of these associations and highlight the need for further research in these relatively understudied waters.

Flexibility in Red Sea Tridacna maxima‐Symbiodiniaceae associations supports environmental niche adaptation

“…In corals, fine‐scale resolutions of Symbiodiniaceae assemblages often strongly correlate to host genotype (Gardner et al., 2019; Howells et al., 2020; Hume, D’Angelo, et al., 2018; Hume et al., 2020). However, if the Red Sea T. maxima populations are assumed to be a single well‐connected, yet diverse population, this would suggest that the prevailing environmental conditions, which are also known to strongly influence coral‐Symbiodiniaceae associations (Hume et al., 2020; LaJeunesse et al., 2010; Oliver & Palumbi, 2009; Smith et al., 2020; Terraneo et al., 2019; Varasteh et al., 2017; Voolstra, Buitrago‐López, et al., 2020; Voolstra, Valenzuela, et al., 2020; Ziegler et al., 2015), are the driving forces of the observed structure. Whether this relatively high clam‐symbiont flexibility is a product of the location in which the algal symbionts reside within the host tissue (i.e., extracellularly in clams vs. intracellularly in corals) remains to be investigated.…”

Fine-scale delineation of Symbiodiniaceae genotypes on a previously bleached central Red Sea reef system demonstrates a prevalence of coral host-specific associations

“…Within the context of molecular identification, the second internal transcribed spacer (ITS2) region of the nrDNA (and to a much lesser extent the ITS1 region Hume et al 2018a) is the most commonly used genetic marker to assess Symbiodiniaceae diversity (e.g., LaJeunesse 2001LaJeunesse , 2002Arif et al 2014;Swain et al 2016;Cunning et al 2017;Varasteh et al 2017;Teschima et al 2019). This can be attributed to the marker's ability to amplify across the entire Symbiodiniaceae taxonomic range using a single set of primers while still being able to resolve at and below the species level (LaJeunesse 2001;Smith et al 2017;Hume et al 2018bHume et al , 2019.…”

SymPortal: A novel analytical framework and platform for coral algal symbiont next‐generation sequencing ITS2 profiling

“…Despite the multitude of markers available for assessing Symbiodiniaceae diversity, the internal transcribed spacer 2 (ITS2) of the rRNA gene shows an uninterrupted popularity and remains the most commonly used marker (Cunning, Gates, & Edmunds, 2017;Fujise et al, 2018;Pochon, Putnam, & Gates, 2014;Smith, Ketchum, & Burt, 2017b;Varasteh, Shokri, Rajabi-Maham, Behzadi, & Hume, 2018). However, this marker is multicopy in nature, which complicates its use.…”

“…Whilst DGGE and to a lesser extent molecular cloning-and-sequencing approaches are still used to analyse the state of rDNA variation (Hume, D'Angelo, Burt, & Wiedenmann, 2018;Smith, Hume, Delaney, Wiedenmann, & Burt, 2017a;Varasteh et al, 2018;Wham, Ning, & LaJeunesse, 2017), contemporary analyses are starkly shifting towards employing next-generation sequencing (NGS) technologies (Cunning et al, 2017;Hume et al, 2016;Hume, Ziegler et al, 2018;Smith, Ketchum et al, 2017b;Ziegler et al, 2017). These NGS approaches afford a greater sequencing depth, but yield sequence diversities orders of magnitude larger than previous methodologies.…”