Diatom primary productivity is tightly coupled with carbon export through the ballasted nature of the silica-based cell wall, linking the oceanic silicon and carbon cycles. However, despite low productivity, iron (Fe)-limited regimes are considered ‘hot spots’ of diatom silica burial with enhanced carbon export efficiency, raising questions about the mechanisms driving the biogeochemistry of these regions. Marine viruses are classically recognized as catalysts of remineralization through host lysis, short-circuiting the trophic transfer of carbon and facilitating the retention of dissolved organic matter and associated elements in the surface ocean. Here we used metatranscriptomic analysis of diatoms and associated viruses, along with a suite of physiological and geochemical metrics, to study the interaction between diatoms and viruses in Fe-limited regimes of the northeast Pacific. We found low cell-associated diatom virus diversity and abundance in a chronically Fe-limited region of the subarctic northeast Pacific. In a coastal upwelling region of the California Current, transient iron limitation also substantially reduced viral replication. These observations were recapitulated in Fe-limited cultures of the bloom-forming, centric diatom, Chaetoceros tenuissimus, which exhibited delayed virus-mediated mortality in addition to reduced viral replication. We suggest Fe-limited diatoms escape viral lysis and subsequent remineralization in the surface ocean, providing an additional mechanism contributing to enhanced carbon export efficiency and silica burial in Fe-limited oceanic regimes.

硅藻的初级生产力通过二氧化硅基细胞壁的压载特性与碳输出密切相关，将海洋硅和碳循环联系起来。然而，尽管生产力低，但铁 (Fe) 限制状态被认为是硅藻二氧化硅掩埋的“热点”，碳输出效率提高，这引发了对这些地区生物地球化学驱动机制的质疑。海洋病毒通常被认为是通过宿主裂解、缩短碳的营养转移并促进溶解的有机物和相关元素在表层海洋中保留的再矿化催化剂。在这里，我们使用了硅藻和相关病毒的宏转录组学分析，以及一套生理和地球化学指标，研究东北太平洋铁限制区硅藻与病毒之间的相互作用。我们在亚北极东北太平洋的一个长期铁含量有限的地区发现了低细胞相关硅藻病毒的多样性和丰度。在加利福尼亚海流的沿海上升流地区，短暂的铁限制也大大减少了病毒复制。这些观察结果在形成花朵的中心硅藻的铁限制培养物中得到了概括，Chaetoceros tenuissimus，除了减少病毒复制外，还表现出病毒介导的死亡率延迟。我们建议铁限制的硅藻在海洋表层中逃避病毒裂解和随后的再矿化，提供了一种额外的机制，有助于提高碳输出效率和在铁限制的海洋环境中埋藏二氧化硅。