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Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate to ammonium reducers

Helen Decleyre (UGent) , Kim Heylen (UGent) and Anne Willems (UGent)
Author
Organization
Abstract
In estuaries, the nitrogen cycle can be substantially altered due to anthropogenic activities resulting in increased amounts of inorganic nitrogen (mainly nitrate). Nitrate can be lost from these systems via anaerobic ammonium oxidation (anammox), denitrification or dissimilatory nitrate reduction to ammonium (DNRA). In the past, denitrification was often viewed as the main ecosystem process that removes reactive N from the ecosystem. However, recent reports on the contribution of DNRA to N removal in these systems indicated similar or higher importance, although the ratio between both processes remains ambiguous. Compared to denitrification, DNRA has been underexplored for the last decades and, despite some attempts, the key organisms carrying out the process in marine environments and their response to increased N loading are largely unknown. Hence, to better understand the relative importance of denitrification, DNRA and reduction of nitrate to nitrite in estuarine sediments, nitrogen reduction potentials were determined. In addition, to increase the availability of marine DNRA representatives, nitrate reducing bacteria were cultivated, identified and the N-reducing metabolism involved was verified. Substantial small scale heterogeneity in dominant N removing processes over a short distance (1.6m) could be observed. N2O production rates appeared to be more or less stable over all 5 sampling sites, while NH4+ and NO2- production rates varied enormously depending on the sampling site. Out of the 35 isolates obtained from estuarine sediments, 15 were able to use nitrate as electron acceptor and all demonstrated a DNRA phenotype. For 12 out of the 15 nitrate reducers, the DNRA phenotype was re-confirmed through nrf gene amplification. To our knowledge, this is the first report that members of Thalassospira, Celeribacter and Halomonas are capable of performing DNRA. The merit of these new isolates is that they provide an alternative to the common model organisms (e.g. E.coli, Wollinella succinogenes) for testing influences of different environmental parameters (e.g. pH, initial NO3+ concentration) on their ability to perform DNRA, i.e. their ecophysiology.

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MLA
Decleyre, Helen, Kim Heylen, and Anne Willems. “Dissimilatory Nitrogen Reduction in Intertidal Sediments of a Temperate Estuary: Small Scale Heterogeneity and Novel Nitrate to Ammonium Reducers.” Nitrogen Cycle, 20th European Meeting, Abstracts. 2015. Print.
APA
Decleyre, H., Heylen, K., & Willems, A. (2015). Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate to ammonium reducers. Nitrogen Cycle, 20th European meeting, Abstracts. Presented at the 20th European Nitrogen Cycle meeting.
Chicago author-date
Decleyre, Helen, Kim Heylen, and Anne Willems. 2015. “Dissimilatory Nitrogen Reduction in Intertidal Sediments of a Temperate Estuary: Small Scale Heterogeneity and Novel Nitrate to Ammonium Reducers.” In Nitrogen Cycle, 20th European Meeting, Abstracts.
Chicago author-date (all authors)
Decleyre, Helen, Kim Heylen, and Anne Willems. 2015. “Dissimilatory Nitrogen Reduction in Intertidal Sediments of a Temperate Estuary: Small Scale Heterogeneity and Novel Nitrate to Ammonium Reducers.” In Nitrogen Cycle, 20th European Meeting, Abstracts.
Vancouver
1.
Decleyre H, Heylen K, Willems A. Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate to ammonium reducers. Nitrogen Cycle, 20th European meeting, Abstracts. 2015.
IEEE
[1]
H. Decleyre, K. Heylen, and A. Willems, “Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate to ammonium reducers,” in Nitrogen Cycle, 20th European meeting, Abstracts, Aberdeen, Scotland, UK, 2015.
@inproceedings{7010314,
  abstract     = {In estuaries, the nitrogen cycle can be substantially altered due to anthropogenic activities resulting in increased amounts of inorganic nitrogen (mainly nitrate). Nitrate can be lost from these systems via anaerobic ammonium oxidation (anammox), denitrification or dissimilatory nitrate reduction to ammonium (DNRA). In the past, denitrification was often viewed as the main ecosystem process that removes reactive N from the ecosystem. However, recent reports on the contribution of DNRA to N removal in these systems indicated similar or higher importance, although the ratio between both processes remains ambiguous. Compared to denitrification, DNRA has been underexplored for the last decades and, despite some attempts, the key organisms carrying out the process in marine environments and their response to increased N loading are largely unknown.	 
Hence, to better understand the relative importance of denitrification, DNRA and reduction of nitrate to nitrite in estuarine sediments, nitrogen reduction potentials were determined. In addition, to increase the availability of marine DNRA representatives, nitrate reducing bacteria were cultivated, identified and the N-reducing metabolism involved was verified. Substantial small scale heterogeneity in dominant N removing processes over a short distance (1.6m) could be observed. N2O production rates appeared to be more or less stable over all 5 sampling sites, while NH4+ and NO2- production rates varied enormously depending on the sampling site. Out of the 35 isolates obtained from estuarine sediments, 15 were able to use nitrate as electron acceptor and all demonstrated a DNRA phenotype. For 12 out of the 15 nitrate reducers, the DNRA phenotype was re-confirmed through nrf gene amplification. To our knowledge, this is the first report that members of Thalassospira, Celeribacter and Halomonas are capable of performing DNRA. The merit of these new isolates is that they provide an alternative to the common model organisms (e.g. E.coli, Wollinella succinogenes) for testing influences of different environmental parameters (e.g. pH, initial NO3+ concentration) on their ability to perform DNRA, i.e. their ecophysiology.},
  author       = {Decleyre, Helen and Heylen, Kim and Willems, Anne},
  booktitle    = {Nitrogen Cycle, 20th European meeting, Abstracts},
  language     = {eng},
  location     = {Aberdeen, Scotland, UK},
  title        = {Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate to ammonium reducers},
  year         = {2015},
}