Article (Scientific journals)
Iron-dependent nitrogen cycling in a ferruginous lake and the nutrient status of Proterozoic oceans
Michiels, Celine C.; Darchambeau, François; Roland, Fleur et al.
2017In Nature Geoscience, 10 (0), p. 217–221
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Abstract :
[en] Nitrogen limitation during the Proterozoic has been inferred from the great expanse of ocean anoxia under low-O2 atmospheres, which could have promoted NO3- reduction to N2 and fixed N loss from the ocean. The deep oceans were Fe rich (ferruginous) during much of this time, yet the dynamics of N cycling under such conditions remain entirely conceptual, as analogue environments are rare today. Here we use incubation experiments to show that a modern ferruginous basin, Kabuno Bay in East Africa, supports high rates of NO3- reduction. Although 60 of this NO3- is reduced to N2 through canonical denitrification, a large fraction (40\%) is reduced to NH4+, leading to N retention rather than loss. We also find that NO3- reduction is Fe dependent, demonstrating that such reactions occur in natural ferruginous water columns. Numerical modelling of ferruginous upwelling systems, informed by our results from Kabuno Bay, demonstrates that NO3- reduction to NH4+ could have enhanced biological production, fuelling sulfate reduction and the development of mid-water euxinia overlying ferruginous deep oceans. This NO3- reduction to NH4+ could also have partly offset a negative feedback on biological production that accompanies oxygenation of the surface ocean. Our results indicate that N loss in ferruginous upwelling systems may not have kept pace with global N fixation at marine phosphorous concentrations (0.04-0.13[thinsp][mu]M) indicated by the rock record. We therefore suggest that global marine biological production under ferruginous ocean conditions in the Proterozoic eon may thus have been P not N limited.
Research center :
FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
Disciplines :
Aquatic sciences & oceanology
Author, co-author :
Michiels, Celine C.
Darchambeau, François ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (AGO)
Roland, Fleur ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (AGO)
Morana, Cédric ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (COU)
Lliros, Marc
Garcia-Armisen, Tamara
Thamdrup, Bo
Borges, Alberto  ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (AGO)
Canfield, Donald E.
Servais, Pierre
Descy, Jean-Pierre ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (COU)
Crowe, Sean A.
Language :
English
Title :
Iron-dependent nitrogen cycling in a ferruginous lake and the nutrient status of Proterozoic oceans
Publication date :
2017
Journal title :
Nature Geoscience
ISSN :
1752-0894
eISSN :
1752-0908
Publisher :
Nature Publishing Group, London, United Kingdom
Volume :
10
Issue :
0
Pages :
217–221
Peer reviewed :
Peer Reviewed verified by ORBi
European Projects :
FP7 - 240002 - AFRIVAL - African river basins: catchment-scale carbon fluxes and transformations.
Name of the research project :
AFRIVAL
Funders :
CE - Commission Européenne [BE]
Commentary :
Article
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since 02 March 2017

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