Abstract
It is well known that different coral species have different tolerances to thermal or cold stress, which is presumed to be related to the density of Symbiodinium. However, the intrinsic factors between stress-tolerant characteristics and coral-associated bacteria are rarely studied. In this study, 16 massive coral and 9 branching coral colonies from 6 families, 10 genera, and 18 species were collected at the same time and location (Xinyi Reef) in the South China Sea to investigate the bacterial communities. The results of an alpha diversity analysis showed that bacterial diversities associated with massive corals were generally higher than those with branching corals at different taxonomic levels (phylum, class, order, and so on). In addition, hierarchical clustering tree and PCoA analyses showed that coral species were clustered into two large groups according to the similarity of bacterial communities. Group I consisted of massive Goniastrea, Plesiastrea, Leptastrea, Platygyra, Echinopora, Porites, and Leptoria, and group II consisted of branching Acropora and Pocillopora. These findings suggested that both massive corals and branching corals have their own preference for the choice of associated bacteria, which may be involved in observed differences in thermal/cold tolerances. Further analysis found that 55 bacterial phyla, including 43 formally described phyla and 12 candidate phyla, were detected in these coral species. Among them, 52 phyla were recovered from the massive coral group, and 46 phyla were recovered from the branching coral group. Formally described coral pathogens have not been detected in these coral species, suggesting that they are less likely to be threatened by disease in this geographic area. This study highlights a clear relationship between the high complexity of bacterial community associated with coral, skeletal morphology of coral and potentially tolerances to thermal or cold stress.
Highlights
Coral-associated microorganisms, including bacteria, fungi, Archaea, dinoflagellates, eukaryotic viruses and phage (Wegley et al, 2007), play significant roles in the biogeochemical cycle, material transformation and maintaining health of coral reef ecosystems (Lesser et al, 2004; Fiore et al, 2010; Mao-Jones et al, 2010; Mahmoud and Kalendar, 2016)
This means that the diversity and equitability of bacteria associated with massive corals (MC) are higher than branching corals (BC)
Our results from this study showed that bacterial diversities associated with MC were generally higher than those associated with BC at different taxonomic levels
Summary
Coral-associated microorganisms, including bacteria, fungi, Archaea, dinoflagellates, eukaryotic viruses and phage (Wegley et al, 2007), play significant roles in the biogeochemical cycle, material transformation and maintaining health of coral reef ecosystems (Lesser et al, 2004; Fiore et al, 2010; Mao-Jones et al, 2010; Mahmoud and Kalendar, 2016). Studies have shown that the diversities of bacterial communities associated with corals are extremely high (Li et al, 2013), and significantly affected by the factors including species (Hong et al, 2009), geography (McKew et al, 2012), season (Chen et al, 2011; Li et al, 2014), and more (Bourne et al, 2008; Ceh et al, 2012). The results indicated that bacterial diversity increased for all coral species after spawning; some bacterial groups (e.g., Roseobacter, Erythrobacter, and Alteromonadales) that may play an important role in coral reproduction were found to be prominent in these coral species (Ceh et al, 2012). Meron et al (2011) further showed that ocean acidification would affect the community structure of coral-associated bacteria, and some potential pathogens, such as Vibrionaceae and Alteromonadaceae, would become active with an increasing abundance
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