Beschreibung:
<jats:title>Summary</jats:title><jats:p>Diazotrophic bacteria potentially play an important functional role in supplying fixed nitrogen to the coral holobiont, but the value of such a partnership depends on the stability of the association. Here we evaluate the composition of diazotroph assemblages associated with the coral <jats:styled-content style="fixed-case"><jats:italic>A</jats:italic></jats:styled-content><jats:italic>cropora</jats:italic><jats:italic> millepora</jats:italic> throughout four seasons and at two reefs, an inshore and an offshore (mid‐shelf) reef on the <jats:styled-content style="fixed-case">G</jats:styled-content>reat <jats:styled-content style="fixed-case">B</jats:styled-content>arrier <jats:styled-content style="fixed-case">R</jats:styled-content>eef, <jats:styled-content style="fixed-case">A</jats:styled-content>ustralia. Amplicon pyrosequencing of the <jats:styled-content style="fixed-case"><jats:italic>nifH</jats:italic></jats:styled-content> gene revealed that diazotrophs are ubiquitous members of the bacterial community associated with <jats:styled-content style="fixed-case"><jats:italic>A</jats:italic></jats:styled-content><jats:italic>. millepora</jats:italic>. Rhizobia (65% of the overall <jats:styled-content style="fixed-case"><jats:italic>nifH</jats:italic></jats:styled-content> sequences retrieved) and particularly <jats:styled-content style="fixed-case"><jats:italic>B</jats:italic></jats:styled-content><jats:italic>radyrhizobia</jats:italic> sp<jats:italic>.‐</jats:italic>affiliated sequences (> 50% of rhizobia sequences) dominated diazotrophic assemblages across all coral samples from the two sites throughout the year. In contrast to this consistency in the spatial and temporal patterns of occurrence of diazotroph assemblages, the overall coral‐associated bacterial community, assessed through amplicon sequencing of the general bacterial 16S ribosomal <jats:styled-content style="fixed-case">RNA</jats:styled-content> gene, differed between inshore and mid‐shelf reef locations. Sequences associated with the <jats:styled-content style="fixed-case"><jats:italic>O</jats:italic></jats:styled-content><jats:italic>ceanospirillales</jats:italic> family, particularly with <jats:styled-content style="fixed-case"><jats:italic>E</jats:italic></jats:styled-content><jats:italic>ndozoicomonas</jats:italic> sp., dominated bacterial communities associated with inshore corals. Although rhizobia represented a variable and generally small fraction of the overall bacterial community associated with <jats:styled-content style="fixed-case"><jats:italic>A</jats:italic></jats:styled-content>. <jats:italic>millepora</jats:italic>, consistency in the structure of these diazotrophic assemblages suggests that they have a functional role in the coral holobiont.</jats:p>