Anaerobic Nitrogen Turnover by Sinking Diatom Aggregates at Varying Ambient Oxygen Levels

Frontiers in Microbiology
Peter StiefRonnie N Glud

Abstract

In the world's oceans, even relatively low oxygen levels inhibit anaerobic nitrogen cycling by free-living microbes. Sinking organic aggregates, however, might provide oxygen-depleted microbial hotspots in otherwise oxygenated surface waters. Here, we show that sinking diatom aggregates can host anaerobic nitrogen cycling at ambient oxygen levels well above the hypoxic threshold. Aggregates were produced from the ubiquitous diatom Skeletonema marinoi and the natural microbial community of seawater. Microsensor profiling through the center of sinking aggregates revealed internal anoxia at ambient 40% air saturation (∼100 μmol O2 L(-1)) and below. Accordingly, anaerobic nitrate turnover inside the aggregates was evident within this range of ambient oxygen levels. In incubations with (15)N-labeled nitrate, individual Skeletonema aggregates produced NO2 (-) (up to 10.7 nmol N h(-1) per aggregate), N2 (up to 7.1 nmol N h(-1)), NH4 (+) (up to 2.0 nmol N h(-1)), and N2O (up to 0.2 nmol N h(-1)). Intriguingly, nitrate stored inside the diatom cells served as an additional, internal nitrate source for dinitrogen production, which may partially uncouple anaerobic nitrate turnover by diatom aggregates from direct ambient nitrate supply. S...Continue Reading

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Citations

Oct 8, 2016·Frontiers in Microbiology·Amanda M AchbergerUNKNOWN WISSARD Science Team
Dec 21, 2017·Frontiers in Microbiology·Clara A FuchsmanGabrielle Rocap
Apr 25, 2019·Environmental Science. Processes & Impacts·Jian ZengYusheng Qiu
Feb 20, 2018·Limnology and Oceanography·Ugo MarzocchiRonnie N Glud
Oct 23, 2019·The ISME Journal·Isabell KlawonnHelle Ploug
Dec 7, 2018·Frontiers in Microbiology·Jeppe N PedersenLasse Riemann
Jul 31, 2018·FEMS Microbiology Ecology·Peter StiefRonnie N Glud
May 15, 2021·Communications Biology·Steven SmrigaAndrew R Babbin
Aug 31, 2021·Annual Review of Marine Science·Anja EngelMarcus Dengler

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Methods Mentioned

BETA
microsensors
microsensor

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