Details zur Publikation

Kategorie Textpublikation
Referenztyp Zeitschriften
DOI 10.1038/s41396-019-0514-9
Lizenz creative commons licence
Titel (primär) Distinct nitrogen cycling and steep chemical gradients in Trichodesmium colonies
Autor Klawonn, I.; Eichner, M.J.; Wilson, S.T.; Moradi, N.; Thamdrup, B.; Kümmel, S.; Gehre, M.; Khalili, A.; Grossart, H.-P.; Karl, D.M.; Ploug, H.
Quelle ISME Journal
Erscheinungsjahr 2020
Department ISOBIO
Band/Volume 14
Heft 2
Seite von 399
Seite bis 412
Sprache englisch
Abstract Trichodesmium is an important dinitrogen (N2)-fixing cyanobacterium in marine ecosystems. Recent nucleic acid analyses indicate that Trichodesmium colonies with their diverse epibionts support various nitrogen (N) transformations beyond N2 fixation. However, rates of these transformations and concentration gradients of N compounds in Trichodesmium colonies remain largely unresolved. We combined isotope-tracer incubations, micro-profiling and numeric modelling to explore carbon fixation, N cycling processes as well as oxygen, ammonium and nitrate concentration gradients in individual field-sampled Trichodesmium colonies. Colonies were net-autotrophic, with carbon and N2 fixation occurring mostly during the day. Ten percent of the fixed N was released as ammonium after 12-h incubations. Nitrification was not detectable but nitrate consumption was high when nitrate was added. The consumed nitrate was partly reduced to ammonium, while denitrification was insignificant. Thus, the potential N transformation network was characterised by fixed N gain and recycling processes rather than denitrification. Oxygen concentrations within colonies were ~60–200% air-saturation. Moreover, our modelling predicted steep concentration gradients, with up to 6-fold higher ammonium concentrations, and nitrate depletion in the colony centre compared to the ambient seawater. These gradients created a chemically heterogeneous microenvironment, presumably facilitating diverse microbial metabolisms in millimetre-sized Trichodesmium colonies.
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Klawonn, I., Eichner, M.J., Wilson, S.T., Moradi, N., Thamdrup, B., Kümmel, S., Gehre, M., Khalili, A., Grossart, H.-P., Karl, D.M., Ploug, H. (2020):
Distinct nitrogen cycling and steep chemical gradients in Trichodesmium colonies
ISME J. 14 (2), 399 - 412 10.1038/s41396-019-0514-9