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Limnology and Oceanography: Methods








Dinitrogen (N2) fixation is an important source of biologically reactive nitrogen (N) to the global ocean. The magnitude of this flux, however, remains uncertain, in part because N2 fixation rates have been estimated following divergent protocols and because associated levels of uncertainty are seldom reported—confounding comparison and extrapolation of rate measurements. A growing number of reports of relatively low but potentially significant rates of N2 fixation in regions such as oxygen minimum zones, the mesopelagic water column of the tropical and subtropical oceans, and polar waters further highlights the need for standardized methodological protocols for measurements of N2 fixation rates and for calculations of detection limits and propagated error terms. To this end, we examine current protocols of the 15N2 tracer method used for estimating diazotrophic rates, present results of experiments testing the validity of specific practices, and describe established metrics for reporting detection limits. We put forth a set of recommendations for best practices to estimate N2 fixation rates using 15N2 tracer, with the goal of fostering transparency in reporting sources of uncertainty in estimates, and to render N2 fixation rate estimates intercomparable among studies.


© 2020 The Authors. Limnology and Oceanography: Methods published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography.

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Data Availability

Article states: "Data from this work are archived with BCO-DMO (Moisander et al. 2019)."

BCO-DMO link to data from Moisander et al. (2019) reference is doi:10.1575/1912/bco-dmo.778000.1

Original Publication Citation

White, A. E., Granger, J., Selden, C., Gradoville, M. R., Potts, L., Bourbonnais, A., ... & Tobias, C. R. (2020). A critical review of the 15N2 tracer method to measure diazotrophic production in pelagic ecosystems. Limnology and Oceanography: Methods, 18(4), 129-147. doi:10.1002/lom3.10353


0000-0001-8819-189X (Mulholland)

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