Nitrogen isotope simulations show the importance of atmospheric iron deposition for nitrogen fixation across the Pacific Ocean

作者：Somes Christopher J^*; Schmittner Andreas; Altabet Mark A

来源：Geophysical Research Letters, 2010, 37: L23605.

DOI：10.1029/2010GL044537

Nitrogen (N) fixation by specialized microorganisms (diazotrophs) influences global plankton productivity because it provides the ocean with most of its bio-available N. However, its global rate and large-scale spatial distribution is still regarded with considerable uncertainty. Here we use a global ocean nitrogen isotope model, in comparison with delta(NO3-)-N-15 observations, to constrain the pattern of N-2 fixation across the Pacific Ocean. N-2 fixation introduces isotopically light atmospheric N-2 from to the ocean (delta N-15 = parts per thousand) relative to the oceanic average near 5 parts per thousand, which makes nitrogen isotopes suitable to infer patterns of N-2 fixation. Including atmospheric iron limitation of diazotrophy in the model shifts the pattern of simulated N-2 fixation from the South Pacific to the North Pacific and from the East Pacific westward. These changes considerably improve the agreement with meridional transects of available delta(NO3-)-N-15 observations, as well as excess P (PO43- - NO3-/16), suggesting that atmospheric iron deposition is indeed important for N fixation in the Pacific Ocean. This study highlights the potential for using d15N observations and model simulations to constrain patterns and rates of N fixation in the ocean. Citation: Somes, C. J., A. Schmittner, and M. A. Altabet (2010), Nitrogen isotope simulations show the importance of atmospheric iron deposition for nitrogen fixation across the Pacific Ocean, Geophys. Res. Lett., 37, L23605, doi:10.1029/2010GL044537.

• 出版日期2010-12-3