Sugar enrichment provides evidence for a role of nitrogen fixation in coral bleaching

Authors

  • Claudia Pogoreutz,

    1. Coral Reef Ecology Group (CORE), Marine Ecology Department, Faculty of Biology and Chemistry (FB 2), University of Bremen, Bremen, Germany
    2. Department of Ecology, Leibniz Center for Tropical Marine Ecology, Bremen, Germany
    3. Red Sea Research Center, Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
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    • These authors contributed equally to this work.
  • Nils Rädecker,

    1. Coral Reef Ecology Group (CORE), Marine Ecology Department, Faculty of Biology and Chemistry (FB 2), University of Bremen, Bremen, Germany
    2. Red Sea Research Center, Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
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    • These authors contributed equally to this work.
  • Anny Cárdenas,

    1. Coral Reef Ecology Group (CORE), Marine Ecology Department, Faculty of Biology and Chemistry (FB 2), University of Bremen, Bremen, Germany
    2. Red Sea Research Center, Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
    3. Department of Biogeochemistry, Leibniz Center for Tropical Marine Ecology, Bremen, Germany
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  • Astrid Gärdes,

    1. Department of Biogeochemistry, Leibniz Center for Tropical Marine Ecology, Bremen, Germany
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  • Christian R. Voolstra,

    Corresponding author
    1. Red Sea Research Center, Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
    • Correspondence

      Christian R. Voolstra, Red Sea Research Center, Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia.

      Email: christian.voolstra@kaust.edu.sa

      and

      Christian Wild, Coral Reef Ecology Group (CORE), Marine Ecology Department, Faculty of Biology and Chemistry, University of Bremen, Germany.

      Email: christian.wild@uni-bremen.de

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  • Christian Wild

    Corresponding author
    1. Coral Reef Ecology Group (CORE), Marine Ecology Department, Faculty of Biology and Chemistry (FB 2), University of Bremen, Bremen, Germany
    2. Department of Ecology, Leibniz Center for Tropical Marine Ecology, Bremen, Germany
    • Correspondence

      Christian R. Voolstra, Red Sea Research Center, Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia.

      Email: christian.voolstra@kaust.edu.sa

      and

      Christian Wild, Coral Reef Ecology Group (CORE), Marine Ecology Department, Faculty of Biology and Chemistry, University of Bremen, Germany.

      Email: christian.wild@uni-bremen.de

    Search for more papers by this author

Abstract

The disruption of the coral–algae symbiosis (coral bleaching) due to rising sea surface temperatures has become an unprecedented global threat to coral reefs. Despite decades of research, our ability to manage mass bleaching events remains hampered by an incomplete mechanistic understanding of the processes involved. In this study, we induced a coral bleaching phenotype in the absence of heat and light stress by adding sugars. The sugar addition resulted in coral symbiotic breakdown accompanied by a fourfold increase of coral-associated microbial nitrogen fixation. Concomitantly, increased N:P ratios by the coral host and algal symbionts suggest excess availability of nitrogen and a disruption of the nitrogen limitation within the coral holobiont. As nitrogen fixation is similarly stimulated in ocean warming scenarios, here we propose a refined coral bleaching model integrating the cascading effects of stimulated microbial nitrogen fixation. This model highlights the putative role of nitrogen-fixing microbes in coral holobiont functioning and breakdown.

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