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<p>Anthropogenic carbon dioxide emissions drive ocean acidification. <i>Trichodesmium</i>, a key marine nitrogen-fixing cyanobacterium, displays contrasting growth responses to ocean acidification across morphotypes: negative in filamentous free trichomes but neutral or positive in colonies. However, lacking mechanistic understanding for these discrepancies has impaired our ability to predict <i>Trichodesmium</i>’s ecophysiological response. Here, we develop ecophysiological models to underpin mechanisms behind these divergent responses. For free trichomes, ocean acidification reduces nitrogen-fixing enzyme activity and photosynthetic energy production. In colonies, however, it alleviates copper and ammonia toxicity within the microenvironment—likely synergizing with enhanced iron acquisition—thereby outweighing minor benefit from relieved inorganic carbon limitation in the colony center. Projections suggest that globally, ocean acidification will reduce nitrogen fixation of trichomes by 16 ± 6% but increase that of colonies by 19 ± 24% within this century. By resolving morphotype-specific mechanisms, our study clarifies <i>Trichodesmium</i>’s adaptive strategies for sustaining its competitiveness and biogeochemical impacts in the changing ocean.</p>

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Colony formation sustains the global competitiveness of nitrogen-fixing Trichodesmium under ocean acidification

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年2月23日

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  • Weicheng Luo,
  • Meri Eichner,
  • Ondřej Prášil,
  • Futing Zhang,
  • Keisuke Inomura,
  • Ya-Wei Luo

摘要

Anthropogenic carbon dioxide emissions drive ocean acidification. Trichodesmium, a key marine nitrogen-fixing cyanobacterium, displays contrasting growth responses to ocean acidification across morphotypes: negative in filamentous free trichomes but neutral or positive in colonies. However, lacking mechanistic understanding for these discrepancies has impaired our ability to predict Trichodesmium’s ecophysiological response. Here, we develop ecophysiological models to underpin mechanisms behind these divergent responses. For free trichomes, ocean acidification reduces nitrogen-fixing enzyme activity and photosynthetic energy production. In colonies, however, it alleviates copper and ammonia toxicity within the microenvironment—likely synergizing with enhanced iron acquisition—thereby outweighing minor benefit from relieved inorganic carbon limitation in the colony center. Projections suggest that globally, ocean acidification will reduce nitrogen fixation of trichomes by 16 ± 6% but increase that of colonies by 19 ± 24% within this century. By resolving morphotype-specific mechanisms, our study clarifies Trichodesmium’s adaptive strategies for sustaining its competitiveness and biogeochemical impacts in the changing ocean.