In the open ocean, elevated carbon flux (ECF) events increase the delivery of particulate carbon from surface waters to the seafloor by severalfold compared to other times of year. Since microbes play central roles in primary production and sinking particle formation, they contribute greatly to carbon export to the deep sea. Few studies, however, have quantitatively linked ECF events with the specific microbial assemblages that drive them. Here, we identify key microbial taxa and functional traits on deep-sea sinking particles that correlate positively with ECF events. Microbes enriched on sinking particles in summer ECF events included symbiotic and free-living diazotrophic cyanobacteria, rhizosolenid diatoms, phototrophic and heterotrophic protists, and photoheterotrophic and copiotrophic bacteria. Particle-attached bacteria reaching the abyss during summer ECF events encoded metabolic pathways reflecting their surface water origins, including oxygenic and aerobic anoxygenic photosynthesis, nitrogen fixation, and proteorhodopsin-based photoheterotrophy. The abundances of some deep-sea bacteria also correlated positively with summer ECF events, suggesting rapid bathypelagic responses to elevated organic matter inputs. Biota enriched on sinking particles during a spring ECF event were distinct from those found in summer, and included rhizaria, copepods, fungi, and different bacterial taxa. At other times over our 3-y study, mid- and deep-water particle colonization, predation, degradation, and repackaging (by deep-sea bacteria, protists, and animals) appeared to shape the biotic composition of particles reaching the abyss. Our analyses reveal key microbial players and biological processes involved in particle formation, rapid export, and consumption, that may influence the ocean’s biological pump and help sustain deep-sea ecosystems.

在开阔的海洋中，与一年中的其他时间相比，升高的碳通量 (ECF) 事件使从地表水向海底输送的颗粒碳增加了数倍。由于微生物在初级生产和下沉颗粒形成中发挥着核心作用，因此它们对向深海输出碳做出了巨大贡献。然而，很少有研究将 ECF 事件与驱动它们的特定微生物组合定量联系起来。在这里，我们确定了与 ECF 事件正相关的深海下沉颗粒的关键微生物分类群和功能特征。夏季 ECF 事件中下沉颗粒上富集的微生物包括共生和自由生活的固氮蓝藻、根际硅藻、光养和异养原生生物以及光异养和共养细菌。在夏季 ECF 事件期间到达深渊的颗粒附着细菌编码了反映其地表水来源的代谢途径，包括有氧和有氧无氧光合作用、固氮和基于蛋白视紫红质的光异养。一些深海细菌的丰度也与夏季 ECF 事件呈正相关，表明深海对有机质输入升高的快速反应。春季 ECF 事件中下沉颗粒上富集的生物群与夏季发现的不同，包括根茎、桡足类、真菌和不同的细菌类群。在我们 3 年研究的其他时间，中水和深水粒子的定殖、捕食、降解和重新包装（通过深海细菌、原生生物和动物）似乎塑造了到达深渊的粒子的生物组成。