Microbiome dynamics in the tissue and mucus of acroporid corals differ in relation to host and environmental parameters

Abstract

Corals are associated with diverse microbial assemblages; however, the spatial-temporal dynamics of intra-species microbial interactions are poorly understood. The coral-associated microbial community varies substantially between tissue and mucus microhabitats; however, the factors controlling the occurrence, abundance, and distribution of microbial taxa over time have rarely been explored for different coral compartments simultaneously. Here, we test (1) differentiation in microbiome diversity and composition between coral compartments (surface mucus and tissue) of two Acropora hosts (A. tenuis and A. millepora) common along inshore reefs of the Great Barrier Reef, as well as (2) the potential linkage between shifts in individual coral microbiome families and underlying host and environmental parameters. Amplicon based 16S ribosomal RNA gene sequencing of 136 samples collected over 14 months, revealed significant differences in bacterial richness, diversity and community structure among mucus, tissue and the surrounding seawater. Seawater samples were dominated by members of the Synechococcaceae and Pelagibacteraceae bacterial families. The mucus microbiome of Acropora spp. was dominated by members of Flavobacteriaceae, Synechococcaceae and Rhodobacteraceae and the tissue was dominated by Endozoicimonaceae. Mucus microbiome in both Acropora species was primarily correlated with seawater parameters including levels of chlorophyll a, ammonium, particulate organic carbon and the sum of nitrate and nitrite. In contrast, the correlation of the tissue microbiome to the measured environmental (i.e., seawater parameters) and host health physiological factors differed between host species, suggesting host-specific modulation of the tissue-associated microbiome to intrinsic and extrinsic factors. Furthermore, the correlation between individual coral microbiome members and environmental factors provides novel insights into coral microbiome-by-environment dynamics and hence has potential implications for current reef restoration and management efforts (e.g. microbial monitoring and observatory programs).

Differential Response of the Microbiome of Pocillopora acuta to Reciprocal Transplantation Within Singapore

“…However, a similarly high abundance of Cyanobacteria was not previously observed in P. acuta from Raffles. The high abundance of Cyanobacteria found in corals from Raffles in this study could be linked to the elevated nitrate concentrations observed there, as Cyanobacteria can process nitrate and has been positively correlated with nitrate concentrations [39]. Elevated Cyanobacteria abundance has been associated with coral reef ecosystem degradation, and some Cyanobacteria can be a precursor to coral disease [40,41].…”

Corals and Sponges Under the Light of the Holobiont Concept: How Microbiomes Underpin Our Understanding of Marine Ecosystems

“…Aside from nutrient cycling and primary productivity in the ocean, marine microbes carry vital functions in host physiology. Microbiomes of several important benthic species have been studied to understand their community structure and function and how they relate to the surrounding environment's microbial pool (Barott et al, 2011;Ainsworth et al, 2015;Campbell et al, 2015;Jensen et al, 2019;Ziegler et al, 2019;Marchioro et al, 2020). Holobionts present a variable microbiome which differs across distinct individuals of the same species, and a core microbiome which is defined as a group of persistent microbes across all individuals of the same species, for which we can infer a potentially vital role in the holobiont (Hernandez-Agreda et al, 2017;Pita et al, 2018).…”

“…Host-associated microbiomes tend to present a clear distinct community composition from the surrounding environment (Barott et al, 2011;Jensen et al, 2019;Marchioro et al, 2020). It was demonstrated that deep-sea corals host highly specific bacterial communities with the most abundant OTUs (operational taxonomic units) only accounting for <0.1% of the surrounding seawater bacterial community (Jensen et al, 2019).…”

“…A recently characterized gammaproteobacterial genus, Endozoicomonas, has attracted attention since the genus (or Endozoicomonas-related bacteria) was reported from various marine invertebrates including corals, sponges, polychetes, ascidians, and mollusks in much higher abundances than in the surrounding sediment or seawater (Shiu and Tang, 2019). In corals, Endozoicomonas dominate the endodermal tissue microbial communities and appear to sustain an intimate and vital relationship with the coral host (Bayer et al, 2013;Neave et al, 2017;Pollock et al, 2018;Marchioro et al, 2020). Indeed, significant decreases of Endozoicomonas abundances in the coral microbiome were observed in diseased corals or following environmental stress (Bourne et al, 2008;Webster et al, 2016).…”

Linking photoacclimation responses and microbiome shifts between depth-segregated sibling species of reef corals

“…Synechococcus is a photoautotrophic cyanobacterium found in surface waters harbouring abundant light. Both corals and their symbiotic algae are known to actively feed on Synechococcus (Jeong et al 2012;McNally et al 2017) which is often found as a member of the coral surface mucus microbiome (Marchioro et al 2020). As a food for corals, it has been suggested that nitrogen-rich Synechococcus cells may increase bleaching recovery and coral health (Meunier et al 2019).…”