19 Jan 2023
19 Jan 2023
Status: this preprint is currently under review for the journal ESSD.

Version 2 of the global oceanic diazotroph database

Zhibo Shao1,, Yangchun Xu1,, Hua Wang1, Weicheng Luo1, Lice Wang1, Yuhong Huang1, and Ya-Wei Luo1 Zhibo Shao et al.
  • 1State Key Laboratory of Marine Environmental Science and College of Ocean and Earth Sciences, Xiamen University, Xiamen, Fujian 361102, China
  • These authors contributed equally.

Abstract. Marine diazotrophs convert dinitrogen (N2) in seawater into bioavailable nitrogen (N), contributing approximately half of the external input of bioavailable N to the global ocean. A global oceanic diazotroph database was previously published in 2012. Here, we compiled version 2 of the database by adding 23,095 in situ measurements of marine diazotrophic abundance and N2 fixation rates published in the past decade, increasing the number of N2 fixation rates and microscopic and qPCR-based diazotrophic abundance data by 140 %, 26 % and 443 %, respectively. Although the updated database expanded spatial coverage considerably, particularly in the Indian Ocean, the data distribution was still not uniform and most data were sampled in the surface Pacific and Atlantic Oceans. By summing the arithmetic means of the N2 fixation rates in each ocean basin, the updated database substantially increased the estimate of global oceanic N2 fixation from 137 ± 9 Tg N yr-1 using the old database to 260 ± 20 Tg N yr-1 (mean ± standard error). However, using geometric means instead, the updated database gave an estimate of global oceanic N2 fixation (60 Tg N yr-1) similar to that estimated from the old database (62 Tg N yr-1), while the new estimate had a larger uncertainty (confidence intervals based on one standard error: 47 – 107 Tg N yr-1 versus 52 – 73 Tg N yr-1), mostly attributable to elevated uncertainties in the Pacific Ocean. An analysis comparing N2 fixation rates measured at the same months and location (1° × 1° grids) showed that the new 15N2 dissolution method obtained N2 fixation rates higher than the conventional 15N2 bubble method in 65 % of cases, with this percentage increasing when the N2 fixation rates were high (> approximately 3 μmol N m-3 d-1 using the 15N2 dissolution method). With greatly increased data points, this version 2 of the global oceanic diazotrophic database can support future studies in marine ecology and biogeochemistry. The database is stored at the Figshare repository ( (Shao et al., 2022).

Zhibo Shao et al.

Status: open (until 16 Mar 2023)

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Zhibo Shao et al.

Data sets

Version 2 of the global oceanic diazotroph database Zhibo Shao, Yangchun Xu, Hua Wang, Weicheng Luo, Lice Wang, Yuhong Huang, and Ya-Wei Luo

Zhibo Shao et al.


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Short summary
N2 fixation by marine diazotrophs is an important bioavailable N source to the global ocean. This updated version of the global oceanic diazotroph database added in situ measurements of N2 fixation rates and microscopic and qPCR-based diazotrophic abundance published in 2012–2022, increasing the number of data points of these parameters by 140 %, 26 % and 443 %, respectively. Tentative estimate of global marine N2 fixation rate using the updated database still showed large uncertainties.