idw – Informationsdienst Wissenschaft

Nachrichten, Termine, Experten

Grafik: idw-Logo
Science Video Project
idw-Abo

idw-News App:

AppStore

Google Play Store



Instance:
Share on: 
06/02/2016 15:42

Bacteria may help some corals survive bleaching events

Eberhard Scholz Pressestelle
Universität Bremen

    Researchers have shown for the first time that some corals surviving bleaching events obtain more nutrients from a particular group of bacteria, which may make the coral more heat-tolerant and enhance their recovery.

    This is the key finding of a new study carried out by an international research team under the supervision of Prof. Dr. Christian Wild (Marine Ecology, University of Bremen, Germany). The study was recently published in the prestigious international journal “Environmental Microbiology”. Dr. Ulisse Cardini, who graduated last year at the University of Bremen and now works as researcher at the University of Vienna (Austria), is the first author of the study.

    Coral bleaching and its linkage to ocean warming

    Warm water corals are animals that grow optimally in water temperatures between ca. 23° and 30 °C. If temperatures exceed this comfort zone, then often coral bleaching occurs. In this process, corals loose most of their color as millions of microalgae that live within the corals leave their animal host. As bleaching occurs, corals are not dead, but in a state of great weakness since they lack the algae that normally provide them with essential energy and nutrients. That is why bleaching often leads to mass mortality of corals, particularly if the heat stress is long-lasting and pronounced. Conversely, corals can re-uptake the microalgae and recover from bleaching when temperatures drop back to normal.

    In recent years, ocean warming in combination with El-Nino phenomena led to a high frequency of extended coral bleaching events with ensuing mass mortality (e.g. 1998 in the Indian Ocean, 2002 in the Pacific Ocean, and 2005 in the Caribbean). At the moment, we are witnessing the worst mass coral bleaching on record affecting all world oceans.

    The important role of bacteria in bleached corals

    The study by Ulisse Cardini, Christian Wild, and others provided evidence supporting the hypothesis that a group of bacteria capable of nitrogen fixation may help their host corals to better survive through heat stress events. In fact, these microbes are able to provide essential nutrients that may be deficient in the coral when their symbiosis with microalgae is heat impaired.

    During field and laboratory experiments at the Northern Red Sea (Aqaba, Jordan) the research team could demonstrate that nitrogen fixation increased by up to 300% in some of the corals exposed to heat stress. However, the outcome of the temperature stress was different in different corals.

    In this context, the highly under-investigated interplay between the coral animals, the symbiotic algae, and the associated bacteria plays an important role and may select winners and losers in the world's coral reefs of the future.

    Publication:
    Cardini et al. (2016) Microbial dinitrogen fixation in coral holobionts exposed to thermal stress and bleaching (in press at Environmental Microbiology).

    Further information:

    Prof. Dr. Christian Wild
    University of Bremen
    Faculty Biology / Chemistry
    Marine Ecology
    Phone. 0421 218 63367
    E-mail: christian.wild@uni-bremen.de

    Dr. Ulisse Cardini
    University of Vienna
    Department of Microbiology and Ecosystem Science
    Division of Microbial Ecology
    www.ulissecardini.info
    Phone: +43 677 61633148
    E-mail: cardini@microbial-ecology.net


    Images

    One of the corals that bleached during the experiment, with the coral polyps expanded.
    One of the corals that bleached during the experiment, with the coral polyps expanded.
    "Dr. Ulisse Cardini"
    None


    Criteria of this press release:
    Business and commerce, Journalists, Scientists and scholars
    Biology, Chemistry, Environment / ecology, Oceanology / climate
    transregional, national
    Research results
    English


     

    One of the corals that bleached during the experiment, with the coral polyps expanded.


    For download

    x

    Help

    Search / advanced search of the idw archives
    Combination of search terms

    You can combine search terms with and, or and/or not, e.g. Philo not logy.

    Brackets

    You can use brackets to separate combinations from each other, e.g. (Philo not logy) or (Psycho and logy).

    Phrases

    Coherent groups of words will be located as complete phrases if you put them into quotation marks, e.g. “Federal Republic of Germany”.

    Selection criteria

    You can also use the advanced search without entering search terms. It will then follow the criteria you have selected (e.g. country or subject area).

    If you have not selected any criteria in a given category, the entire category will be searched (e.g. all subject areas or all countries).