Equatorial upwelling of phosphorus drives Atlantic N2 fixation and Sargassum blooms

Abstract The Great Atlantic Sargassum Belt first appeared in 2011 and quickly became the largest interconnected floating biome on Earth. In recent years, Sargassum stranding events have caused substantial ecological and socio-economic impacts in coastal communities. Sargassum requires both phosphorus (P) and nitrogen (N) for growth, yet the primary sources of these nutrients fuelling the extensive Sargassum blooms remain unclear. Here we use coral-bound N isotopes to reconstruct N 2 fixation, the ultimate source of the ocean’s bioavailable N, across the Caribbean over the past 120 years. Our data indicate that changes in N 2 fixation were primarily controlled by multidecadal and interannual changes in equatorial Atlantic upwelling of ‘excess P’, that is, P in stoichiometric excess relative to fixed N. We show that the supply of excess P from equatorial upwelling and N from the N 2 fixation response can account for the majority of Sargassum variability since 2011. Sargassum dynamics are best explained by their symbiosis with N 2 -fixing epiphytes, which render the macroalgae highly competitive during strong equatorial upwelling of excess P. Thus, the future of Sargassum in the tropical Atlantic will depend on how global warming affects equatorial Atlantic upwelling and the climatic modes that control it.

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Publication Details

Journal
Nature Geoscience
Published
2025-11-05
DOI
https://doi.org/10.1038/s41561-025-01812-2
Citations
3
Primary Topic
Marine and coastal plant biology
Type
article
Field-Weighted Citation Impact
5.38

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article

Equatorial upwelling of phosphorus drives Atlantic N2 fixation and Sargassum blooms

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3 citations
Nature Geoscience
Marine and coastal plant biology
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article

Equatorial upwelling of phosphorus drives Atlantic N2 fixation and Sargassum blooms

Hans A. Slagter, Isabella Hrabě de Angelis, Diego K. Kersting, Denis Scholz, Christina Treinen-Crespo, Nicolas Duprey, Jonathan Jung, Hedy M. Aardema, Tanja Wald, Erin L. Murphy, Alan Foreman, Ralf Schiebel, Chuanmin Hu, Jos Lelieveld, Gerald H. Haug, Daniel M. Sigman, Ulrich Pöschl, Miguel Gómez-Batista, Reia Guppy, Juan Pablo D’Olivo, François Fripiat, Hubert Vonhof, Maria Rosabelle Ong, Carlos Manuel Alonso-Hernandez, Maayan Yehudai, Gabriel O. Cardoso, Baseerat Romshoo, José D. Carriquiry, Carlos Jiménez, Andrea Pozzer, Nathalie F. Goodkin, Brian B. Barnes, Kennedy James, Eberhard Gischler, Aaron L. Bieler, Lena Heins, Yeongjun Ryu, Paolo Montagna, Alfredo Martínez‐García, Christopher Pöhlker, Carolin Pellio, Trevor P. Noël
article en
3 citations

Abstract

Abstract The Great Atlantic Sargassum Belt first appeared in 2011 and quickly became the largest interconnected floating biome on Earth. In recent years, Sargassum stranding events have caused substantial ecological and socio-economic impacts in coastal communities. Sargassum requires both phosphorus (P) and nitrogen (N) for growth, yet the primary sources of these nutrients fuelling the extensive Sargassum blooms remain unclear. Here we use coral-bound N isotopes to reconstruct N 2 fixation, the ultimate source of the ocean’s bioavailable N, across the Caribbean over the past 120 years. Our data indicate that changes in N 2 fixation were primarily controlled by multidecadal and interannual changes in equatorial Atlantic upwelling of ‘excess P’, that is, P in stoichiometric excess relative to fixed N. We show that the supply of excess P from equatorial upwelling and N from the N 2 fixation response can account for the majority of Sargassum variability since 2011. Sargassum dynamics are best explained by their symbiosis with N 2 -fixing epiphytes, which render the macroalgae highly competitive during strong equatorial upwelling of excess P. Thus, the future of Sargassum in the tropical Atlantic will depend on how global warming affects equatorial Atlantic upwelling and the climatic modes that control it.

Nature GeoscienceVol. 18(12)
Goethe University Frankfurt (DE), Planetary Science Institute (US), Université Libre de Bruxelles (BE), American Museum of Natural History (US), International University of Monaco (MC), Cyprus Institute (CY), Lamont-Doherty Earth Observatory (US), University of Cienfuegos (CU), Universidad Autónoma de Baja California (MX), University of Trinidad and Tobago (TT), Johannes Gutenberg University Mainz (DE), Princeton University (US), Ocean Conservancy (US), ETH Zurich (CH), Instituto de Acuicultura Torre de la Sal (ES), Windward Islands Research and Education Foundation (GD), Max Planck Institute for Chemistry (DE), Scientific Centre of Monaco (MC), National Research Council (IT), Arizona State University (US), University of South Florida St. Petersburg (US), Freie Universität Berlin (DE), Columbia University (US), College of Marin (US), Universidad Nacional Autónoma de México (MX)
National Science Foundation, National Aeronautics and Space Administration, Deutsche Forschungsgemeinschaft, Fonds De La Recherche Scientifique - FNRS, Nuclear Safety and Security Commission, Max-Planck-Gesellschaft, Universidad de Costa Rica
Openalex Percentile: Top 4%
Marine and coastal plant biology
5.38
DOIOpen Access PDFOpenAlex
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