Intracellular nitrate storage by diatoms can be an important nitrogen pool in freshwater and marine ecosystems

Peter Stief*, Clemens Schauberger, Marie B. Lund, Andreas Greve, Raeid M.M. Abed, Mohammad A.A. Al-Najjar, Karl Attard, Stefano Bonaglia, Jörg S. Deutzmann, Belén Franco-Cisterna, Emilio García-Robledo, Moritz Holtappels, Uwe John, Adele Maciute, Michael J. Magee, Rie Pors, Tina Santl-Temkiv, Anja Scherwass, Duygu S. Sevilgen, Dirk de BeerRonnie N. Glud, Andreas Schramm, Anja Kamp

*Corresponding author for this work

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Identifying and quantifying nitrogen pools is essential for understanding the nitrogen cycle in aquatic ecosystems. The ubiquitous diatoms represent an overlooked nitrate pool as they can accumulate nitrate intracellularly and utilize it for nitrogen assimilation, dissipation of excess photosynthetic energy, and Dissimilatory Nitrate Reduction to Ammonium (DNRA). Here, we document the global co-occurrence of diatoms and intracellular nitrate in phototrophic microbial communities in freshwater (n = 69), coastal (n = 44), and open marine (n = 4) habitats. Diatom abundance and total intracellular nitrate contents in water columns, sediments, microbial mats, and epilithic biofilms were highly significantly correlated. In contrast, diatom community composition had only a marginal influence on total intracellular nitrate contents. Nitrate concentrations inside diatom cells exceeded ambient nitrate concentrations ∼100–4000-fold. The collective intracellular nitrate pool of the diatom community accounted for <1% of total nitrate in pelagic habitats and 65–95% in benthic habitats. Accordingly, nitrate-storing diatoms are emerging as significant contributors to benthic nitrogen cycling, in particular through Dissimilatory Nitrate Reduction to Ammonium activity under anoxic conditions.

Original languageEnglish
Article number154
JournalCommunications Earth and Environment
Issue number1
Number of pages11
Publication statusPublished - Jul 2022


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