Changes in the Potential Activity of Nitrite Reducers and the Microbial Community Structure After Sediment Dredging and Plant Removal in the Empuriabrava FWS-CW


In constructed wetlands (CW), denitrification usually accounts for > 60% of nitrogen removal and is supposedly affected by wetland management practices, such as dredging (and plant removal). These practices cause an impact in sediment properties and microbial communities living therein. We have quantified the effects of a sediment dredging event on dissimilatory nitrite reduction by analysing the structure and activities of the microbial community before and after the event. Potential rates for nitrate reduction to ammonia and denitrification were in accordance with changes in the physicochemical conditions. Denitrification was the predominant pathway for nitrite removal (> 60%) and eventually led to the complete removal of nitrate. On the contrary, dissimilatory nitrite reduction to ammonia (DNRA) increased from 5 to 18% after the dredging event. Both actual activities and abundances of 16S rRNA, nirK and nirS significantly decreased after sediment dredging. However, genetic potential for denitrification (qnirS + qnirK/q16S rRNA) remained unchanged. Analyses of the 16S rRNA gene sequences revealed the importance of vegetation in shaping microbial community structures, selecting specific phylotypes potentially contributing to the nitrogen cycle. Overall, we confirmed that sediment dredging and vegetation removal exerted a measurable effect on the microbial community, but not on potential nitrite + nitrate removal rates. According to redundancy analysis, nitrate concentration and pH were the main variables affecting sediment microbial communities in the Empuriabrava CWs. Our results highlight a high recovery of the functionality of an ecosystem service after a severe intervention and point to metabolic redundancy of denitrifiers. We are confident these results will be taken into account in future management strategies in CWs.

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The authors are grateful to Lluís Sala Genoher (Consorci d’Aigües Costa Brava, and the personnel at the EDAR-Empuriabrava for providing field data and access to the sampling area. Ariadna Vilar-Sanz and Laia Mauricio are acknowledged for assisting in field work and initial processing of samples.


EHdA received a grant from the University of Girona (IF-UDG2013). This work was funded by the Spanish Ministry (CGL2009-08338/BOS) and the University of Girona (MPCUdG2016/121). IEA has been recognised as a consolidated research group by the Catalan Government (2017SGR-548).

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All authors conceived and planned the experiments. EHdA, SRP and FG carried out the experiments. EHdA, FG, SRP, LB and RT assisted in field work. EHdA and SRP prepared the samples and performed chemical and kinetic determinations. EHdA, FG and RT conducted molecular work. EHdA, FG and LB contributed to the interpretation of the results. EHdA drafted the manuscript. All authors contributed to the discussion and review of the manuscript providing critical feedback. LB and FG approved the submission.

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Correspondence to Lluís Bañeras.

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Hernández-del Amo, E., Ramió-Pujol, S., Gich, F. et al. Changes in the Potential Activity of Nitrite Reducers and the Microbial Community Structure After Sediment Dredging and Plant Removal in the Empuriabrava FWS-CW. Microb Ecol 79, 588–603 (2020).

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  • Denitrification
  • DNRA
  • Constructed wetland
  • Nitrite reductase
  • Potential activity
  • Microbial community
  • Sediment dredging
  • Aquatic macrophytes