In situ denitrification rates from a salt marsh after sediment addition

Abstract Salt marshes globally are rapidly being outpaced by sea level rise. One strategy used to boost marsh elevation is thin layer sediment placement (also known as TLP). Yet the impact of TLP on marsh nitrogen cycling largely remains unknown. To address this knowledge gap, we used the push‐pull and isotope pairing technique to measure in situ growing season rates of denitrification in experimental TLP and control plots in a temperate salt marsh. We found that median total (ambient + direct) denitrification was ~ 1.5 times greater in the TLP plots compared to the control, though this difference was not statistically significant. Direct denitrification was dominant in the TLP plots. In contrast, coupled nitrification–denitrification accounted for ~ 60% of the denitrification in the control plots. These data suggest that in addition to boosting elevation, sediment addition also preserves important biogeochemical functions such as the capacity for nitrogen removal.