Abstract
A coral's capacity to alter its microbial symbionts may enhance its fitness in the face of climate change. Recent work predicts exposure to high environmental variability may increase coral resilience and adaptability to future climate conditions. However, how this heightened environmental variability impacts coral-associated microbial communities remains largely unexplored. Here, we examined the bacterial and algal symbionts associated with two coral species of the genus Siderastrea with distinct life history strategies from three reef sites on the Belize Mesoamerican Barrier Reef System with low or high environmental variability. Our results reveal bacterial community structure, as well as alpha- and beta-diversity patterns, vary by host species. Differences in bacterial communities between host species were partially explained by high abundance of Deltaproteobacteria and Rhodospirillales and high bacterial diversity in Siderastrea radians. Our findings also suggest Siderastrea spp. have dynamic core bacterial communities that likely drive differences observed in the entire bacterial community, which may play a critical role in rapid acclimatization to environmental change. Unlike the bacterial community, Symbiodiniaceae composition was only distinct between host species at high thermal variability sites, suggesting that different factors shape bacterial versus algal communities within the coral holobiont. Our findings shed light on how domain-specific shifts in dynamic microbiomes may allow for unique methods of enhanced host fitness.
Highlights
The coral holobiont is comprised of the coral animal and its phylogenetically diverse symbiotic partners including algae, bacteria, archaea, fungi, viruses, and protists (Forest Rohwer, Seguritan, Azam, & Knowlton, 2002)
Within-host beta diversity of bacterial communities differed between host species, with S. radians samples showing lower β-diversity than S. siderea samples (Table S4, permutest: P
Our findings demonstrate that the bacterial community composition (BCC) of two Caribbean coral species in the genus Sidereastrea are shaped by deterministic factors, including host species (Fig 1 and Table S4)
Summary
The coral holobiont is comprised of the coral animal and its phylogenetically diverse symbiotic partners including algae, bacteria, archaea, fungi, viruses, and protists (Forest Rohwer, Seguritan, Azam, & Knowlton, 2002). G. Bourne, Morrow, & Webster, 2016) They prevent disease by occupying niches that could otherwise be colonized by opportunistic pathogens, as well as by producing antimicrobials (Ritchie, 2006; Rypien, Ward, & Azam, 2010), and acting as a pseudo-adaptive immune system for the entire holobiont (Palmer, 2018). Disease and reduced fitness often result when coral-bacterial associations break down due to biotic or abiotic stressors (Terry P Hughes et al, 2003; Sogin, Putnam, Nelson, Anderson, & Gates, 2017)
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