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Environ Microbiol. 2019 Jan;21(1):480-495. doi: 10.1111/1462-2920.14480. Epub 2018 Dec 19.

Diazotrophic community and associated dinitrogen fixation within the temperate coral Oculina patagonica.

Author information

1
Marine Department, Centre Scientifique de Monaco, 8 Quai Antoine Ier, MC-98000, Monaco, Principality of Monaco.
2
Sorbonne Universités, UPMC Univ Paris 06, UMR 7093, LOV, Observatoire océanologique, F-06230, Villefranche/mer, France.
3
CNRS, UMR 7093, LOV, Observatoire océanologique, F-06230, Villefranche/mer, France.
4
LEMAR - UMR 6539 UBO/CNRS/IRD, Institut Universitaire Européen de la Mer, Place Nicolas Copernic, Plouzané 29280, France.

Abstract

Dinitrogen (N2 ) fixing bacteria (diazotrophs) are an important source of new nitrogen in oligotrophic environments and represent stable members of the microbiome in tropical corals, while information on corals from temperate oligotrophic regions is lacking. Therefore, this study provides new insights into the diversity and activity of diazotrophs associated with the temperate coral Oculina patagonica from the Mediterranean Sea by combining metabarcoding sequencing of amplicons of both the 16S rRNA and nifH genes and 15 N2 stable isotope tracer analysis to assess diazotroph-derived nitrogen (DDN) assimilation by the coral. Results show that the diazotrophic community of O. patagonica is dominated by autotrophic bacteria (i.e. Cyanobacteria and Chlorobia). The majority of DDN was assimilated into the tissue and skeletal matrix, and DDN assimilation significantly increased in bleached corals. Thus, diazotrophs may constitute an additional nitrogen source for the coral host, when nutrient exchange with Symbiodinium is disrupted (e.g. bleaching) and external food supply is limited (e.g. oligotrophic summer season). Furthermore, we hypothesize that DDN can facilitate the fast proliferation of endolithic algae, which provide an alternative carbon source for bleached O. patagonica. Overall, O. patagonica could serve as a good model for investigating the importance of diazotrophs in coral recovery from bleaching.

PMID:
30452101
DOI:
10.1111/1462-2920.14480

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