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Significance of N2 fixation in dissolved fractions of organic nitrogen
1Earth and Planetary System Science, Faculty of Science, Hokkaido University, N10 W8, Sapporo 060-0810, Japan
2Ocean Research Institute, University of Tokyo, Tokyo 164 8639, Japan
3Faculty of Environmental Earth Science, Hokkaido University, N10 W5, Sapporo 060-0810, Japan
Abstract. Using the 15N2 tracer method and high-sensitivity δ15N analytical systems, we determined N2 fixation rates by dividing fractions into particulate organic nitrogen (PON: >0.7 μm) and dissolved organic nitrogen (DON: <0.7 μm). While N2 fixation in the DON fraction had been ignored in previous studies, we found significant N2 fixation signal in the DON fraction in our study. The areal N2 fixation rates estimated from the PON fractions varied from <1–160 μmol N m−2 d−1, and those estimated from the DON fractions ranged from <0.5–54 μmol N m−2 d−1. Thus, N2 fixation in the DON fractions accounted for 50% (ranging from <10% to 84%) of the total N2 fixation rates on an average. The new total N2 fixation flux, which includes fixation in DON fractions, has possibility to double the original estimates; therefore, the revised influx may reduce the imbalance in the global oceanic fixed nitrogen budget.
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Citation: Konno, U., Tsunogai, U., Komatsu, D. D., Daita, S., Nakagawa, F., Tsuda, A., Matsui, T., Eum, Y.-J., and Suzuki, K.: Significance of N2 fixation in dissolved fractions of organic nitrogen, Biogeosciences Discuss., 7, 765-786, 2010. Bibtex EndNote Reference Manager
