An evaluation of isotope dilution effect from conventional data sets of ¹⁵N uptake experiments

Abstract

A practical calculation procedure to correct the underestimate caused by isotope dilution in 15 N uptake experiments is described. The estimate is based on the experimental observation of 15 N incorporation into particuUtc organic matter but not on direct measurement of isotope enrichment in the substrate. Conventional data sets of 15 N uptake and an estimate of the ratio of the flux of regeneration and uptake can provide the information needed to correct for isotope dilution. Application of this method to 15 NH 4+ uptake data in the literature showed that the underestimate is small in open ocean waters but sometimes substantial in coastal or estuarine waters.