South China Sea Annual Meeting 2023 (SCSAM)

47 / 2023-07-24 15:08:05

Elevated estimation for global marine N2 fixation based on new measurements in the past decade

Estimation of N2 fixation; Diazotrophic database; N2 fixation rate

The contribution of marine diazotrophs in converting dinitrogen (N2) into bioavailable nitrogen (N) is crucial for sustaining life in the global ocean. A global diazotroph database was previously published in 2012. With the contribution from nearly 100 scientists, the version 2 of the database has been compiled by incorporating more than 40,000 additional in situ measurements of marine diazotrophic abundance and N2 fixation rates from the last decade. The updated database has expanded spatial coverage considerably, although data distribution remains uneven. Based on mean N2 fixation rate in each ocean basin, the updated database suggests an increase in the estimate of global oceanic N2 fixation from 74 (95% confidence interval: 56 – 102) Tg N yr-1 to 223 (95% confidence interval: 144 – 402) Tg N yr-1. The elevated estimate is mainly attributed to high N2 fixation newly observed in the last decade in the South Pacific and North Atlantic Oceans. To better estimate the global N2 fixation rate, the quantitative relationship between the observed N2 fixation and environmental factors are analyzed and constructed. The new version of the database can facilitate future studies in marine ecology and biogeochemistry, and is stored at a public repository.