Age-Related Shifts in Bacterial Diversity in a Reef Coral

Abstract

This study investigated the relationship between microbial communities in differently sized colonies of the massive coral Coelastrea aspera at Phuket, Thailand where colony size could be used as a proxy for age. Results indicated significant differences between the bacterial diversity (ANOSIM, R = 0.76, p = 0.001) of differently sized colonies from the same intertidal reef habitat. Juvenile and small colonies (<6cm mean diam) harboured a lower bacterial richness than medium (~10cm mean diam) and large colonies (>28 cm mean diam). Bacterial diversity increased in a step-wise pattern from juveniles<small<medium colonies, which was then followed by a slight decrease in the two largest size classes. These changes appear to resemble a successional process which occurs over time, similar to that observed in the ageing human gut. Furthermore, the dominant bacterial ribotypes present in the tissues of medium and large sized colonies of C. aspera, (such as Halomicronema, an Oscillospira and an unidentified cyanobacterium) were also the dominant ribotypes found within the endolithic algal band of the coral skeleton; a result providing some support for the hypothesis that the endolithic algae of corals may directly influence the bacterial community present in coral tissues.

Evidence for rapid, tide-related shifts in the microbiome of the coral Coelastrea aspera

“…Such exposure causes severe oxidative damage within coral tissues during extreme low tides (Brown et al 2002). In recent work, we have also highlighted age-related changes in the microbiome of C. aspera, with the highest microbial diversity in 4-to 12-yr-old corals (Williams et al 2015). Here we describe the community responses of the coral microbiome in two age classes (4-yr-old and 10-yrold colonies) over a 4-d spring-tide sequence.…”

“…The large tidal range ([3 m) means that during spring tides, waters leave the reef flat very rapidly (within 20 min), and during the dry season salinity effects induced by the tidal regime are therefore negligible, with the salinity of surface waters varying between 31 and 34% (Charuchinda and Hylleberg 1984). Two age classes of C. aspera (as outlined in Williams et al 2015) were identified on the reef flat to compare microbial communities throughout a tidal cycle in March 2014. Colony ages were determined through alizarin staining, skeleton chronology and by following the demography of this coral population from their initial settlement in the early 1990s (Brown et al 2014;Williams et al 2015).…”

“…Two age classes of C. aspera (as outlined in Williams et al 2015) were identified on the reef flat to compare microbial communities throughout a tidal cycle in March 2014. Colony ages were determined through alizarin staining, skeleton chronology and by following the demography of this coral population from their initial settlement in the early 1990s (Brown et al 2014;Williams et al 2015). The age classes selected were *4-yr-old and *10-yr-old corals (Williams et al 2015).…”

“…Colony ages were determined through alizarin staining, skeleton chronology and by following the demography of this coral population from their initial settlement in the early 1990s (Brown et al 2014;Williams et al 2015). The age classes selected were *4-yr-old and *10-yr-old corals (Williams et al 2015). The 4-yr-old corals were hemispherical colonies showing no partial mortality, while the 10-yr-old corals were micro-atolls with *30-40% mortality.…”

“…However, recently it has been recognized that, in addition to the algal symbionts, corals also host a highly diverse and specific microbiome which includes bacteria, archaea, fungi, protists and viruses (Rohwer et al 2002). Much less is known about this coral microbiome, particularly with respect to the dynamics of microbial partners through coral development (Thompson et al 2014), aging (Williams et al 2015) and their responses to changing environments (Morrow et al 2012;Hester et al 2015;Glasl et al 2016;Röthig et al 2016).…”