Characterization of the Microbiome of Corals with Stony Coral Tissue Loss Disease along Florida's Coral Reef.

Abigail S Clark,Sara D Williams,Lindsay K Huebner,Jan H Landsberg,Erinn M Muller,Stephanie M Rosales,John H Hunt,Kerry Maxwell

doi:10.3390/microorganisms9112181

Abstract

Stony coral tissue loss disease (SCTLD) is an emergent and often lethal coral disease that was first reported near Miami, FL (USA) in 2014. Our objective was to determine if coral colonies showing signs of SCTLD possess a specific microbial signature across five susceptible species sampled in Florida’s Coral Reef. Three sample types were collected: lesion tissue and apparently unaffected tissue of diseased colonies, and tissue of apparently healthy colonies. Using 16S rRNA high-throughput gene sequencing, our results show that, for every species, the microbial community composition of lesion tissue was significantly different from healthy colony tissue and from the unaffected tissue of diseased colonies. The lesion tissue of all but one species (Siderastrea siderea) had higher relative abundances of the order Rhodobacterales compared with other types of tissue samples, which may partly explain why S. siderea lesions often differed in appearance compared to other species. The order Clostridiales was also present at relatively high abundances in the lesion tissue of three species compared to healthy and unaffected tissues. Stress often leads to the dysbiosis of coral microbiomes and increases the abundance of opportunistic pathogens. The present study suggests that Rhodobacterales and Clostridiales likely play an important role in SCTLD.

Highlights

Corals host a diversity of microorganisms composed of viruses, fungi, archaea, endolithic algae, protozoa, bacteria, and algal symbionts [1,2,3,4,5]
A permutational multivariate analysis of variance (PERMANOVA) test found that bacterial communities of tissue sampled from apparently healthy (AH) colonies in the vulnerable zone were significantly different from the bacterial communities associated with AH tissue in the epidemic zone for each species: Colpophyllia natans (Figure 3A; F1,16 = 1.6007, R2 = 0.06298, p = 0.0053), Pseudodiploria strigosa (Figure 3B; F1,15 = 2.6, R2 = 0.1044, p < 0.0001), Montastraea cavernosa (Figure 3C; F1,15 = 1.7394, R2 = 0.07, p = 0.0002), Orbicella faveolata (Figure 3D; F1,15 = 2.4137, R2 = 0.09132, p < 0.0001), and Siderastrea siderea (Figure 3E; F1,15 = 1.935, R2 = 0.07603, p < 0.0001)
As a result of the differences across zones and among sites, the amplicon sequence variants (ASVs) generated from colonies in the vulnerable zone were analyzed independently of ASVs associated with the epidemic zone

Summary

Introduction

Corals host a diversity of microorganisms composed of viruses, fungi, archaea, endolithic algae, protozoa, bacteria, and algal symbionts [1,2,3,4,5]. Microbes living in or on a coral can be beneficial to the coral host by playing important roles in the cycling and recycling of nutrients [6,7,8], the production of amino acids [8,9], protection against pathogens [10,11], and enhancing larval settlement and metamorphosis [12] Disturbances, such as those caused by climate change, can alter coral–microbe interactions and lead to bleaching, disease, and the mortality of the coral host [13,14,15]. As a result of these stressors and others (e.g., sedimentation), there has been an increase in widespread bleaching events, disease incidence, and subsequent mortality among coral communities in recent decades [18,19,20,21,22].

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Conclusion