Effects of experimental warming and carbon addition on nitrate reduction and respiration in coastal sediments

Abstract

higher effects of C addition compared to warming. Combined warming and C addition had the 30 strongest effect on nitrate flux across the sediment water interface, with a complete switch early 31 in the experiment from influx to sustained efflux. Supporting this result, vial incubations with 32 added 15 N-nitrate indicated that C addition stimulated potential rates of dissimilatory nitrate 33 reduction to ammonium (DNRA), but not denitrification. Overall capacity for both 34 denitrification and DNRA was reduced in warmed treatments, possibly reflecting C losses due to 35 increased respiration with warming. Anammox potential rates were much lower than DNRA or 36 denitrification, and were slightly negatively affected by warming or C addition. Overall, results 37 indicate that warming and C addition increased ammonium production through remineralization 38 and possibly DNRA. This stimulated nitrate production through nitrification, but without a 39 comparable increase in nitrate consumption through denitrification. The response to C of 40 potential DNRA rates over denitrification, along with a switch to nitrate efflux, raises the 41 possibility that DNRA is an important and previously overlooked source of internal N cycling in 42 shelf sediments. 43Nitrate reduction in coastal sediments 3 Introduction 44

Effect of Temperature on Oxygen Profiles and Denitrification Rates in Freshwater Sediments

“…The weaker temperature effect indicates that other drivers besides temperature are of importance in controlling denitrification rates. This corroborates the findings of Brin et al (2015) and Hanke et al (2015), who both showed that availability of organic carbon is another key determinant controlling denitrification and its response to warming. In our experiment nitrate concentrations were set at 1 mg N l −1 at the start of the denitrification measurements.…”

Ecology and physiology of anaerobic ammonium oxidizing bacteria

“…The most influential environmental parameter is the dissolved oxygen (DO) concentration (Jensen et al, 2008;Kalvelage et al, 2011;Dalsgaard et al, 2012;Brabandere et al, 2014). In addition to DO, the following environmental parameters influenced the abundance of anammox bacteria and/or anammox activities: NOx − concentration (Risgaard-Petersen et al, 2004;Rich et al, 2008;Nicholls and Trimmer, 2009;Dang et al, 2010;Rush et al, 2012;Teixeira et al, 2012;Kalvelage et al, 2013;Zhu et al, 2013), salinity (Rich et al, 2008;Koop-Jakobsen and Giblin, 2009;Wang and Gu, 2013a,b;Sonthiphand et al, 2014), sulfide concentration (Wakeham et al, 2007;Jensen et al, 2008;), sediment reactivity (Nicholls and Trimmer, 2009;Li et al, 2013;Bale et al, 2014;Lisa et al, 2014), manganese oxide levels (Engström et al, 2005), temperature (Teixeira et al, 2012;Brin et al, 2015), the molar ratio of NH4 + to NOx − Li et al, 2013) and pH (Hu et al, 2012a;Li et al, 2013;Wang and Gu, 2013a,b). It is possible that these environmental parameters also affect the microbial activities of competitors who consumed NH3 or NO2 − (i.e.…”

DNRA and Denitrification Coexist over a Broad Range of Acetate/N-NO3− Ratios, in a Chemostat Enrichment Culture

“…For a long time, DNRA received little consideration in studies of nitrate respiration in natural and man-made ecosystems, like wastewater treatment plants. In the last decade, interest in DNRA increased since N-labeling experiments have indicated that DNRA may play a significant role in the N-cycling (Burgin and Hamilton, 2007; Kraft et al, 2011; Rütting et al, 2011; Brin et al, 2015). Although, the physiology and bioenergetics of DNRA are relatively well studied in a selected number of pure cultures, the (quantitative) role of DNRA in the environment is one of the least described of the nitrogen cycle processes (Streminska et al, 2012).…”