期刊
GEOPHYSICAL RESEARCH LETTERS
卷 42, 期 11, 页码 4482-4489出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2015GL063756
关键词
marine N2 fixation; marine biogeochemical modeling; phytoplankton coexistence; marine N cycle; North Atlantic
资金
- Deutsche Forschungsgemeinschaft DFG [LA2919/1-1]
- DFG [SFB754]
Growing slowly, marine N-2 fixers are generally expected to be competitive only where nitrogen (N) supply is low relative to that of phosphorus (P) with respect to the cellular N:P ratio (R) of nonfixing phytoplankton. This is at odds with observed high N-2 fixation rates in the oligotrophic North Atlantic where the ratio of nutrients supplied to the surface is elevated in N relative to the average R (16:1). In this study, we investigate several mechanisms to solve this puzzle: iron limitation, phosphorus enhancement by preferential remineralization or stoichiometric diversity of phytoplankton, and dissolved organic phosphorus (DOP) utilization. Combining resource competition theory and a global coupled ecosystem-circulation model, we find that the additional N and energy investments required for exoenzymatic breakdown of DOP give N-2 fixers a competitive advantage in oligotrophic P-starved regions. Accounting for this mechanism expands the ecological niche of N-2 fixers also to regions where the nutrient supply is high in N relative to R, yielding, in our model, a pattern consistent with the observed high N-2 fixation rates in the oligotrophic North Atlantic.
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