Successive shifts in the microbial community of the surface mucus layer and tissues of the coralAcropora muricataunder thermal stress

Abstract

The coral mucus may harbor commensal bacteria that inhibit growth of pathogens. Therefore, there is a need to understand the dynamics of bacterial communities between the coral mucus and tissues. Nubbins of Acropora muricata were subjected to increasing water temperatures of 26°C-33°C, to simultaneously explore the bacterial diversity in coral mucus and tissues by 16S rRNA gene amplicon sequencing. Photochemical efficiency of symbiotic dinoflagellates within the corals declined above 31°C. Both the mucus and tissues of healthy A. muricata were dominated by γ-Proteobacteria, but under thermal stress there was a shift towards bacteria from the Verrucomicrobiaceae and α-Proteobacteria. Members of Cyanobacteria, Flavobacteria and Sphingobacteria also become more prominent at higher temperatures. The relative abundance of Vibrio spp. in the coral mucus increased at 29°C, but at 31°C, there was a drop in the relative abundance of Vibrio spp. in the mucus, with a reciprocal increase in the tissues. On the other hand, during bleaching, the relative abundance of Endozoicomonas spp. decreased in the tissues with a reciprocal increase in the mucus. This is the first systematic experiment that shows the potential for a bacterial community shift between the coral surface mucus and tissues in a thermally stressed coral.

Allelochemicals Produced by Brown Macroalgae of the Lobophora Genus Are Active against Coral Larvae and Associated Bacteria, Supporting Pathogenic Shifts to Vibrio Dominance

“…declined in the tissues of Acropora muricata and increased in the mucus, with a concurrent increase in Vibrio spp. in both the tissues and mucus (57). These studies provide additional evidence that stress may cause a shift in and/or loss of key members of the coral microbiome that can coincide with a shift to a community dominated by opportunistic and fast-growing bacteria.…”

The Assimilation of Diazotroph-Derived Nitrogen by Scleractinian Corals Depends on Their Metabolic Status

“…An increased seawater temperature also increases the abundance and diversity of coral-associated diazotrophs, shifting toward a more heat-resistant diazotroph community (62). Also, the bacterial community associated with the mucus undergoes drastic changes when exposed to heat stress (63). In the present study, 15 N 2 incubations with S. pistillata (bleached) were conducted after the heat stress period under normal temperature conditions.…”

Intergenerational effects of macroalgae on a reef coral: major declines in larval survival but subtle changes in microbiomes

“…In support of this hypothesis, we found similarly high relative abundances (>80%) of Endozoicimonaceae bacteria in adult P. damicornis coral from both healthy and degraded reefs. Recent evidence suggests that these bacteria are functionally important members of the healthy coral holobiont in multiple coral species (Meyer et al 2014, Lee et al 2015, Ding et al 2016, Neave et al 2016), including P. damicornis (Bayer et al 2013). We also detected similar abundances of Endozoicimonacaeae (1–12%) on larvae from both the MPA and fished area, adding further support for the hypothesized importance of these bacteria in P. damicornis persistence.…”