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<p>The Great Atlantic <i>Sargassum</i> Belt first appeared in 2011 and quickly became the largest interconnected floating biome on Earth. In recent years, <i>Sargassum</i> stranding events have caused substantial ecological and socio-economic impacts in coastal communities. <i>Sargassum</i> requires both phosphorus (P) and nitrogen (N) for growth, yet the primary sources of these nutrients fuelling the extensive <i>Sargassum</i> blooms remain unclear. Here we use coral-bound N isotopes to reconstruct N<sub>2</sub> 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<sub>2</sub> 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<sub>2</sub> fixation response can account for the majority of <i>Sargassum</i> variability since 2011. <i>Sargassum</i> dynamics are best explained by their symbiosis with N<sub>2</sub>-fixing epiphytes, which render the macroalgae highly competitive during strong equatorial upwelling of excess P. Thus, the future of <i>Sargassum</i> in the tropical Atlantic will depend on how global warming affects equatorial Atlantic upwelling and the climatic modes that control it.</p>

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Equatorial upwelling of phosphorus drives Atlantic N2 fixation and Sargassum blooms

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年11月5日

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

摘要

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 N2 fixation, the ultimate source of the ocean’s bioavailable N, across the Caribbean over the past 120 years. Our data indicate that changes in N2 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 N2 fixation response can account for the majority of Sargassum variability since 2011. Sargassum dynamics are best explained by their symbiosis with N2-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.