Abstract

BackgroundCoral reefs have sustained damage of increasing scale and frequency due to climate change, thereby intensifying the need to elucidate corals’ biological characteristics, including their thermal tolerance and microbial symbioses. The sea anemone, Exaiptasia diaphana, has proven an ideal coral model for many studies due to its close phylogenetic relationship and shared traits, such as symbiosis with algae of the family Symbiodiniaceae. However, established E. diaphana clonal lines are not available in Australia thus limiting the ability of Australian scientists to conduct research with this model. To help address this, the bacterial and Symbiodiniaceae associates of four Great Barrier Reef (GBR)-sourced E. diaphana genotypes established in laboratory aquaria and designated AIMS1–4, and from proxies of wild GBR E. diaphana were identified by metabarcoding of the bacterial 16S rRNA gene and eukaryotic rRNA gene ITS2 region. The relationship between AIMS1–4 and their bacterial associates was investigated, as was bacterial community phenotypic potential. Existing data from two existing anemone clonal lines, CC7 and H2, were included for comparison.ResultsOverall, 2238 bacterial amplicon sequence variants (ASVs) were observed in the AIMS1–4 bacterial communities, which were dominated by Proteobacteria and Bacteroidetes, together comprising > 90% relative abundance. Although many low abundance bacterial taxa varied between the anemone genotypes, the AIMS1–4 communities did not differ significantly. A significant tank effect was identified, indicating an environmental effect on the microbial communities. Bacterial community richness was lower in all lab-maintained E. diaphana compared to the wild proxies, suggesting a reduction in bacterial diversity and community phenotypic potential due to culturing. Seventeen ASVs were common to every GBR lab-cultured anemone, however five were associated with the Artemia feedstock, making their specific association to E. diaphana uncertain. The dominant Symbiodiniaceae symbiont in all GBR anemones was Breviolum minutum.ConclusionDespite differences in the presence and abundance of low abundance taxa, the bacterial communities of GBR-sourced lab-cultured E. diaphana are generally uniform and comparable to communities reported for other lab-cultured E. diaphana. The data presented here add to the global E. diaphana knowledge base and make an important contribution to the establishment of a GBR-sourced coral model organism.

Highlights

  • Coral reefs have sustained damage of increasing scale and frequency due to climate change, thereby intensifying the need to elucidate corals’ biological characteristics, including their thermal tolerance and microbial symbioses

  • Three samples contained high relative abundances of Amplicon Sequence Variant (ASV) from putatively contaminant bacterial taxa from the Enterobacteriaceae and Vibrionaceae (See Supplementary Figure S7, Additional file 3). These three samples were removed from further analyses, leaving 4401 ASVs across all sample types and 2238 ASVs associated with the AIMS1–4 anemones

  • The Great Barrier Reef (GBR)-sourced, lab-cultured E. diaphana in this study were generally consistent with previous model and wild proxy E. diaphana in terms of dominant bacterial associates, and resident Symbiodiniaceae

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Summary

Introduction

Coral reefs have sustained damage of increasing scale and frequency due to climate change, thereby intensifying the need to elucidate corals’ biological characteristics, including their thermal tolerance and microbial symbioses. The loss of the coral’s energyproducing algal endosymbionts, a process known as bleaching, has increased in frequency and severity due to elevated sea surface temperatures (SST) caused by rising atmospheric greenhouse gas concentrations [3] This has led to widespread coral mortality and damage to reef systems [4], and has heightened the need to investigate mitigation solutions. As reefs succumb to the impacts of climate change, the need for a model organism to assist coral research has never been greater This need has been met in the form of the tropical sea anemone, Exaiptasia diaphana (previously Aiptasia pallida [5, 6]). None are available in Australia hampering the ability of Australian researchers to use this model for laboratory-based research and, a native Australian E. diaphana model is urgently needed

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