Journal Article10.1038/NATURE02550
Iron and phosphorus co-limit nitrogen fixation in the eastern tropical North Atlantic
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TL;DR: The results support the hypothesis that aeolian mineral dust deposition promotes nitrogen fixation in the eastern tropical North Atlantic and show that community primary productivity was nitrogen-limited, and that nitrogen fixation was co-limited by iron and phosphorus.
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Abstract: The role of iron in enhancing phytoplankton productivity in high nutrient, low chlorophyll oceanic regions was demonstrated first through iron-addition bioassay experiments1 and subsequently confirmed by large-scale iron fertilization experiments2. Iron supply has been hypothesized to limit nitrogen fixation and hence oceanic primary productivity on geological timescales3, providing an alternative to phosphorus as the ultimate limiting nutrient4. Oceanographic observations have been interpreted both to confirm and refute this hypothesis5, 6, but direct experimental evidence is lacking7. We conducted experiments to test this hypothesis during the Meteor 55 cruise to the tropical North Atlantic. This region is rich in diazotrophs8 and strongly impacted by Saharan dust input9. Here we show that community primary productivity was nitrogen-limited, and that nitrogen fixation was co-limited by iron and phosphorus. Saharan dust addition stimulated nitrogen fixation, presumably by supplying both iron and phosphorus10, 11. Our results support the hypothesis that aeolian mineral dust deposition promotes nitrogen fixation in the eastern tropical North Atlantic.
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Citations
Cross-Basin Comparison of Phosphorus Stress and Nitrogen Fixation in Trichodesmium
TL;DR: The phosphorus (P) status and N2 fixation rates of Trichodesmium populations from the North Pacific, western South Pacific, and western North Atlantic are investigated and suggest that factors other than P are constraining their N1 fixation rates in the Pacific.
Phosphorus cycling in the Sargasso Sea: Investigation using the oxygen isotopic composition of phosphate, enzyme-labeled fluorescence, and turnover times
TL;DR: The data suggests that in the euphotic zone of the Sargasso Sea, DOP may be appreciably remineralized and utilized by phytoplankton and bacteria to supplement cellular requirements.
Diazotrophic bacteria respond to Saharan dust additions
TL;DR: The results with both field and laboratory experiments indicate that Saharan dust positively affects diazotrophic phylotype abundances and changes T. erythraeum colony morphology.
Assessment of Excess Nitrate Development in the Subtropical North Atlantic
TL;DR: In this article, the authors investigate the variability in published estimates of excess nitrogen accumulation rates in the main thermocline of the subtropical North Atlantic, testing the assumptions and choices made in the analyses, and determine a total excess N accumulation rate of 7.8 ± 1.7 × 1011 mol N yr− 1.
57
New insights into the distributions of nitrogen fixation and diazotrophs revealed by high-resolution sensing and sampling methods.
Weiyi Tang,Elena Cerdán-García,Hugo Berthelot,Despo Polyviou,Seaver Wang,Alison J. Baylay,Hannah Whitby,Hannah Whitby,Hélène Planquette,Matthew C. Mowlem,Julie Robidart,Nicolas Cassar,Nicolas Cassar +12 more
TL;DR: Over this iron-replete transect spanning the western North Atlantic, the results suggest that temperature is the major factor controlling the diazotrophic community structure while phosphorous drives N 2 fixation rates.
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