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Application of the isotope pairing technique in sediments where anammox and denitrification coexist
Author(s) -
RisgaardPetersen Nils,
Nielsen Lars Peter,
Rysgaard Søren,
Dalsgaard Tage,
Meyer Rikke Louise
Publication year - 2003
Publication title -
limnology and oceanography: methods
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.898
H-Index - 72
ISSN - 1541-5856
DOI - 10.4319/lom.2003.1.63
Subject(s) - anammox , denitrification , sediment , chemistry , slurry , environmental chemistry , environmental science , isotope , soil science , nitrogen , environmental engineering , geology , physics , denitrifying bacteria , quantum mechanics , paleontology , organic chemistry
The isotope pairing technique (IPT) is a well‐established 15N method for estimation of denitrification. Presence of anammox, the anaerobic oxidation of NH 4 + to N 2 with NO 2 − results in violation of central assumptions on which the IPT is built. It is shown that anammox activity causes overestimation of the N 2 production calculated by the IPT. However, experiments with different additions of 15 NO 3 − will reveal the problems posed by anammox. Two alternative calculation procedures are presented, which enable a more accurate quantification of anammox and denitrification activity in sediments where the processes coexist. One procedure is based on measurements of 15 N ‐ N 2 production in 15 NO x − ‐amended intact sediment cores and data addressing the contribution of anammox to total N 2 production estimated from slurry incubations. The other procedure is based on measurements of 15 N 2 production in at least two parallel series of sediment cores incubated with different 15 NO x − additions. The calculation procedure presented is used on field data from four studies where the IPT was used and the potential anammox rate measured. The IPT overestimated total 14N‐ N 2 production rates by 0%, 2.5%, 31%, and 82% relative to the revised estimates from the 4 different sites, where anammox accounted for 0%, 6%, 18%, and 69.8%, respectively, of N 2 production. The overestimation of true denitrification was, however, up to several hundred percent. Our analysis suggests however that the IPT does not seriously overestimate N 2 production in estuarine sediments because anammox accounts for <6% of N 2 production in such sediments, according to present knowledge.