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<p>Fungal parasites are associated with bloom-forming algae, yet their impact on N<sub>2</sub> fixation and the fate of newly fixed nitrogen during cyanobacterial blooms is poorly understood. We report infections on the ecologically important N<sub>2</sub>-fixing cyanobacterium <i>Dolichospermum</i> (formerly <i>Anabaena</i>) in the Baltic Sea. Using single-cell isotope probing, microscopy, and biogeochemical analyses, we examine how infections affect carbon and N<sub>2</sub> fixation and elemental transfer within a natural community. Fungal sporangia infect up to 80% of filaments, mostly targeting storage cells (akinetes, 82% prevalence) and N<sub>2</sub>-fixing cells (heterocytes, 44%), but rarely vegetative cells (5%). Infections at akinete–heterocyte junctions extract 4- and 10-fold more carbon and nitrogen than those on vegetative cells, reducing host storage by 28% and 56%. Overall, 22% of newly fixed nitrogen is transferred to fungi, comparable to heterotrophic bacteria. Infections also occur in<i> Nodularia</i> and <i>Aphanizomenon</i>, suggesting fungi-like parasitism broadly affects bloom dynamics and the fate of new nitrogen.</p>

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Fungal parasites infecting N2-fixing cyanobacteria reshape carbon and N2 fixation and trophic transfer

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月2日

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  • Anna Feuring,
  • Connor D. Lawrence,
  • Jessica Salcedo,
  • Martin J. Whitehouse,
  • Angela Vogts,
  • Luca Zoccarato,
  • Isabell Klawonn

摘要

Fungal parasites are associated with bloom-forming algae, yet their impact on N2 fixation and the fate of newly fixed nitrogen during cyanobacterial blooms is poorly understood. We report infections on the ecologically important N2-fixing cyanobacterium Dolichospermum (formerly Anabaena) in the Baltic Sea. Using single-cell isotope probing, microscopy, and biogeochemical analyses, we examine how infections affect carbon and N2 fixation and elemental transfer within a natural community. Fungal sporangia infect up to 80% of filaments, mostly targeting storage cells (akinetes, 82% prevalence) and N2-fixing cells (heterocytes, 44%), but rarely vegetative cells (5%). Infections at akinete–heterocyte junctions extract 4- and 10-fold more carbon and nitrogen than those on vegetative cells, reducing host storage by 28% and 56%. Overall, 22% of newly fixed nitrogen is transferred to fungi, comparable to heterotrophic bacteria. Infections also occur in Nodularia and Aphanizomenon, suggesting fungi-like parasitism broadly affects bloom dynamics and the fate of new nitrogen.