The impact of bio-irrigation on the isotopic signature of benthic inorganic nitrogen fluxes

Abstract

A high degree of isotope fractionation is inherent to denitrification. However, studies have indicated that this is not expressed in sediments due to complete consumption of the nitrate pool. Yet as long as there is an efflux of NO3 from the sediment, fractionation may occur even if the sediment acts as a net nitrate sink. We conducted a model study to determine whether active pumping by the lugworm Arenicola marina allows N isotope fractionation during benthic denitrification. Our results indicate that a significant degree of fractionation may occur and that the production of light N2 is enhanced by coupled nitrification-denitrification.