Coupled nitrogen and oxygen isotope fractionation of nitrate during assimilation by cultures of marine phytoplankton

• DOI: 10.4319/lo.2004.49.5.1763
• Publication Date: 2010-07-01T22:15:08Z
• Authors: Julie Granger; Daniel M. Sigman; Joseph A. Needoba; Paul J. Harrison
• Keywords: Thalassiosira pseudonana; Thalassiosira weissflogii; Nitrogen Assimilation; Isotopes of nitrogen

We report the first measurements of coupled nitrogen (N) and oxygen (O) isotopic variations nitrate (NO ) during its assimilation by laboratory cultures marine phytoplankton derive N O kinetic isotope effects for three species diatoms ( Thalassiosira weissflogii , oceanica pseudonana a coccolithophorid Emiliana huxleyi ). Large interspecies intraspecies in were observed. The effect associated with consumption was consistently close to effect, such that 18 O/ 16 15 N/ 14 varied ratio ~1 : 1, regardless or magnitude effect. In addition, internal T. grown under various environmental conditions elevated relative medium proportion 1. These findings are consistent fractionation mechanism involves reduction as chief fractionating step. observed N:O coupling suggests combined water column can provide new constraints on ocean cycle.