Abstract
Coral disease is one of the major causes of reef degradation. Dark Spot Syndrome (DSS) was described in the early 1990's as brown or purple amorphous areas of tissue on a coral and has since become one of the most prevalent diseases reported on Caribbean reefs. It has been identified in a number of coral species, but there is debate as to whether it is in fact the same disease in different corals. Further, it is questioned whether these macroscopic signs are in fact diagnostic of an infectious disease at all. The most commonly affected species in the Caribbean is the massive starlet coral Siderastrea siderea. We sampled this species in two locations, Dry Tortugas National Park and Virgin Islands National Park. Tissue biopsies were collected from both healthy colonies and those with dark spot lesions. Microbial-community DNA was extracted from coral samples (mucus, tissue, and skeleton), amplified using bacterial-specific primers, and applied to PhyloChip G3 microarrays to examine the bacterial diversity associated with this coral. Samples were also screened for the presence of a fungal ribotype that has recently been implicated as a causative agent of DSS in another coral species, but the amplifications were unsuccessful. S. siderea samples did not cluster consistently based on health state (i.e., normal versus dark spot). Various bacteria, including Cyanobacteria and Vibrios, were observed to have increased relative abundance in the discolored tissue, but the patterns were not consistent across all DSS samples. Overall, our findings do not support the hypothesis that DSS in S. siderea is linked to a bacterial pathogen or pathogens. This dataset provides the most comprehensive overview to date of the bacterial community associated with the scleractinian coral S. siderea.
Highlights
Diseases of reef-building corals are considered a major cause of global coral reef ecosystem decline [1,2]
The most variable family across all samples was the Vibrionaceae, which appeared slightly higher in some Dark Spot Syndrome (DSS) samples from the Virgin Islands (VIISSSD06, VIISSSD08, VIISSSD09, and VIISSSD10), and was enriched in a healthy sample (VIISSH05) (Fig. 3, Fig. S2)
Less variation was observed across the other major families represented on the PhyloChip G3 and detected in these samples: Aquabacteriaceae, Bacillaceae, Comamonadaceae, Corynebacteriaceae, Enterobacteriaceae, Flavobacteriaceae, Lachnospiraceae, Micrococcaceae, Phyllobacteriaceae, Planctomycetaceae, Pseudoalteromonadaceae, Pseudomonadaceae, Rhizobiaceae, Rhodobacteraceae, Rhodospirillaceae, Rikenellaceae II, Ruminococcaceae, Staphylococcaceae, Streptococcaceae, and Ulvophyceae (Fig. 3)
Summary
Diseases of reef-building corals are considered a major cause of global coral reef ecosystem decline [1,2]. The past two decades have seen a dramatic increase in the number of reports of coral diseases, in the Caribbean [3,4,5]. Most of these diseases are known or suspected to be microbial in origin [6]. Microbiology is a key part of coral biology, in the same way that human microbiome studies are revealing microbes to be a critical part of human biology [7]. Siderastera siderea, known as the massive starlet coral, is a common component of Caribbean reefs, occurring from the Gulf of Mexico to South America [8]. There has been little attention focused on the bacterial communities associated with this coral, other than one culture-based study [9], two clone library studies focused on black band lesions [10,11] and a recent pyrosequencing study of a white plague-like disease [12]
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