Stream drying drives microbial ammonia oxidation and first-flush nitrate export

Stephanie N. Merbt, Lorenzo Proia, James I. Prosser, Eugenia Marti, Emilio O. Casamayor, Daniel von Schiller

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38 Citations (Scopus)
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Stream microbial communities and associated processes are influenced by environmental fluctuations that may ultimately dictate nutrient export. Discharge fluctuations caused by intermittent stream flow are increasing worldwide in response to global change. We examined the impact of flow cessation and drying on in-stream nitrogen cycling. We determined archaeal (AOA) and bacterial ammonia oxidiser (AOB) abundance and ammonia oxidation activity in surface and deep sediments from different sites along the Fuirosos stream (Spain) subjected to contrasting hydrological conditions (i.e. running water, isolated pools and dry streambeds). AOA were more abundant than AOB, with no major changes across hydrological conditions or sediment layers. However, ammonia oxidation activity and sediment nitrate content increased with the degree of stream drying, especially in surface sediments. Upscaling of our results shows that ammonia oxidation in dry streambeds can contribute considerably (~50%) to the high nitrate export typically observed in intermittent streams during first flush events following flow reconnection. Our study illustrates how the dry channels of intermittent streams can be potential hotspots of ammonia oxidation. Consequently, shifts in the duration, spatial extent and severity of intermittent flow can play a decisive role in shaping nitrogen cycling and export along fluvial networks in response to global change.
Original languageEnglish
Pages (from-to)2192-2198
Number of pages7
Issue number9
Early online date1 Sept 2016
Publication statusPublished - Sept 2016

Bibliographical note


We thank Roser Ventosa for technical assistance at the Nutrient Analytical Service of the CEAB-CSIC, Unai Perez de Arenaza Basauri for field assistance and Iñaki Odriozola and Aitor Larrañaga for statistical advice. We also acknowledge two anonymous reviewers for valuable feedback and constructive comments on the manuscript. S. N. Merbt was supported by a JAE predoctoral fellowship from the Spanish National Research Council (CSIC). This research was granted by the projects DARKNESS (CGL2012-32747, MINECO) to E. O. Casamayor and MED_FORESTREAM (CGL2011-30590-CO2-02, MINECO) and REFRESH (244121 FP7 EU Commission) to E. Martí.


  • semiarid ecosystems
  • intermittent flow
  • stream
  • dry riverbed
  • nitrification
  • ammonia oxidation
  • ammonia oxidizing archaea (AOA)
  • ammonia oxidizing bacteria (AOB)


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