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Diatoms respire nitrate to survive dark and anoxic conditions

MPS-Authors
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Kamp,  A.
Permanent Research Group Microsensor, Max Planck Institute for Marine Microbiology, Max Planck Society;

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de Beer,  D.
Permanent Research Group Microsensor, Max Planck Institute for Marine Microbiology, Max Planck Society;

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Nitsch,  J. L.
Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Max Planck Society;

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Lavik,  G.
Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Max Planck Society;

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Stief,  P.
Permanent Research Group Microsensor, Max Planck Institute for Marine Microbiology, Max Planck Society;

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Kamp11.pdf
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Citation

Kamp, A., de Beer, D., Nitsch, J. L., Lavik, G., & Stief, P. (2011). Diatoms respire nitrate to survive dark and anoxic conditions. Proceedings of the National Academy of Sciences of the United States of America, 108(14), 5649-5654.


Cite as: http://hdl.handle.net/21.11116/0000-0001-C9A3-4
Abstract
Diatoms survive in dark, anoxic sediment layers for months to decades. Our investigation reveals a correlation between the dark survival potential of marine diatoms and their ability to accumulate NO3− intracellularly. Axenic strains of benthic and pelagic diatoms that stored 11–274 mM NO3− in their cells survived for 6–28 wk. After sudden shifts to dark, anoxic conditions, the benthic diatom Amphora coffeaeformis consumed 84–87% of its intracellular NO3− pool within 1 d. A stable-isotope labeling experiment proved that 15NO3− consumption was accompanied by the production and release of 15NH4+, indicating dissimilatory nitrate reduction to ammonium (DNRA). DNRA is an anaerobic respiration process that is known mainly from prokaryotic organisms, and here shown as dissimilatory nitrate reduction pathway used by a eukaryotic phototroph. Similar to large sulfur bacteria and benthic foraminifera, diatoms may respire intracellular NO3− in sediment layers without O2 and NO3−. The rapid depletion of the intracellular NO3− storage, however, implies that diatoms use DNRA to enter a resting stage for long-term survival. Assuming that pelagic diatoms are also capable of DNRA, senescing diatoms that sink through oxygen-deficient water layers may be a significant NH4+ source for anammox, the prevalent nitrogen loss pathway of oceanic oxygen minimum zones.