Basin-wide N2 fixation in the deep waters of the Mediterranean Sea

Mar Benavides; Sophie Bonnet; Nauzet Hernández; Alba María Martínez-Pérez; Mar Nieto-Cid; Xosé Antón Álvarez-Salgado; Isabel Baños; María F. Montero; Ignacio P. Mazuecos; Josep M. Gasol; Helena Osterholz; Thorsten Dittmar; Ilana Berman-Frank; Javier Arístegui

doi:10.1002/2015GB005326

Basin-wide N₂ fixation in the deep waters of the Mediterranean Sea

Mar Benavides, Sophie Bonnet, Nauzet Hernández, Alba María Martínez-Pérez, Mar Nieto-Cid, Xosé Antón Álvarez-Salgado, Isabel Baños, María F. Montero, Ignacio P. Mazuecos, Josep M. Gasol, Helena Osterholz, Thorsten Dittmar, Ilana Berman-Frank, Javier Arístegui

The Mina and Everard Goodman Faculty of Life Sciences - at Bar-Ilan University

Research output: Contribution to journal › Article › peer-review

40 Scopus citations

Abstract

Recent findings indicate that N₂ fixation is significant in aphotic waters, presumably due to heterotrophic diazotrophs depending on organic matter for their nutrition. However, the relationship between organic matter and heterotrophic N₂ fixation remains unknown. Here we explore N₂ fixation in the deep chlorophyll maximum and underneath deep waters across the whole Mediterranean Sea and relate it to organic matter composition, characterized by optical and molecular methods. Our N₂ fixation rates were in the range of those previously reported for the euphotic zone of the Mediterranean Sea (up to 0.43 nmol N L⁻¹ d⁻¹) and were significantly correlated to the presence of relatively labile organic matter with fluorescence and molecular formula properties representative for peptides and unsaturated aliphatics and associated with the presence of more oxygenated ventilated water masses. Finally, and despite that the aphotic N₂ fixation contributes largely to total water column diazotrophic activity (>50%), its contribution to overall nitrogen inputs to the basin is negligible (<0.5%).

Original language	English
Pages (from-to)	952-961
Number of pages	10
Journal	Global Biogeochemical Cycles
Volume	30
Issue number	6
DOIs	https://doi.org/10.1002/2015GB005326
State	Published - 1 Jun 2016

Bibliographical note

Publisher Copyright:
©2016. American Geophysical Union. All Rights Reserved.

Funding

The data included in this study are available from the authors on request. This work was supported by project HOTMIX—“Dark-ocean water mass boundaries and mixing zones as “hot-spots” of biodiversity and biogeochemical fluxes across the Mediterranean Sea and Eastern North Atlantic”—(CTM2011-30010-C02-01 and CTM2011-30010-C02-02) to J.A., X.A.A.S., and J.M.G. M.B. was funded by the Marie Sklodowska-Curie Actions of the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement 625185. S.B. was funded by the Institut de Recherche pour le Développement (IRD). A.M.M.-P. was funded by FPI and short stay fellowships from the Spanish Ministry of Economy and Competitiveness. M.N.-C. was supported by the CSIC Program “Junta para la Ampliación de Estudios” cofinanced by the ESF. I.B-F. was supported by a collaborative grant with S.B. from MOST Israel and the High Council for Science and Technology (HCST)-France. We are grateful to the captain and crew of the R/V Sarmiento de Gamboa and the staff of the Unit of Marine Technology from the Spanish Research Council (UTM-CSIC), as well as O. Grosso for his help with IRMS analyses and K. Klaproth for her help with FT-ICR-MS analysis. The authors declare no conflict of interest.

Funders	Funder number
Junta para la Ampliación de Estudios
Mediterranean Sea and Eastern North Atlantic	CTM2011-30010-C02-02, CTM2011-30010-C02-01
UTM-CSIC
Seventh Framework Programme	625185
Institut de recherche pour le développement
Family Process Institute
HORIZON EUROPE Marie Sklodowska-Curie Actions
Ministry of Science, Technology and Space
Ministerio de Economía y Competitividad
Consejo Superior de Investigaciones Científicas
European Social Fund
Seventh Framework Programme
Higher Council for Science and Technology

Keywords

diazotrophy

Access to Document

10.1002/2015GB005326

Cite this

Benavides, M., Bonnet, S., Hernández, N., Martínez-Pérez, A. M., Nieto-Cid, M., Álvarez-Salgado, X. A., Baños, I., Montero, M. F., Mazuecos, I. P., Gasol, J. M., Osterholz, H., Dittmar, T., Berman-Frank, I., & Arístegui, J. (2016). Basin-wide N₂ fixation in the deep waters of the Mediterranean Sea. Global Biogeochemical Cycles, 30(6), 952-961. https://doi.org/10.1002/2015GB005326

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abstract = "Recent findings indicate that N2 fixation is significant in aphotic waters, presumably due to heterotrophic diazotrophs depending on organic matter for their nutrition. However, the relationship between organic matter and heterotrophic N2 fixation remains unknown. Here we explore N2 fixation in the deep chlorophyll maximum and underneath deep waters across the whole Mediterranean Sea and relate it to organic matter composition, characterized by optical and molecular methods. Our N2 fixation rates were in the range of those previously reported for the euphotic zone of the Mediterranean Sea (up to 0.43 nmol N L−1 d−1) and were significantly correlated to the presence of relatively labile organic matter with fluorescence and molecular formula properties representative for peptides and unsaturated aliphatics and associated with the presence of more oxygenated ventilated water masses. Finally, and despite that the aphotic N2 fixation contributes largely to total water column diazotrophic activity (>50%), its contribution to overall nitrogen inputs to the basin is negligible (<0.5%).",

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Benavides, M, Bonnet, S, Hernández, N, Martínez-Pérez, AM, Nieto-Cid, M, Álvarez-Salgado, XA, Baños, I, Montero, MF, Mazuecos, IP, Gasol, JM, Osterholz, H, Dittmar, T, Berman-Frank, I & Arístegui, J 2016, 'Basin-wide N₂ fixation in the deep waters of the Mediterranean Sea', Global Biogeochemical Cycles, vol. 30, no. 6, pp. 952-961. https://doi.org/10.1002/2015GB005326

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AU - Bonnet, Sophie

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AU - Martínez-Pérez, Alba María

AU - Nieto-Cid, Mar

AU - Álvarez-Salgado, Xosé Antón

AU - Baños, Isabel

AU - Montero, María F.

AU - Mazuecos, Ignacio P.

AU - Gasol, Josep M.

AU - Osterholz, Helena

AU - Dittmar, Thorsten

AU - Berman-Frank, Ilana

AU - Arístegui, Javier

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