The remineralization depth of sinking organic particles controls the efficiency of the biological carbon pump by setting the sequestration timescale of remineralized carbon in the ocean interior. Oxygen minimum zones (OMZs) have been identified as regions of elevated particle transfer and efficient carbon sequestration at depth, but direct measurements remain sparse in these regions and only provide snapshots of the particle flux. Here, we use remineralization tracers to reconstruct time-mean particle flux profiles in the OMZs of the Eastern Tropical Pacific and the Arabian Sea. Compared to the surrounding tropical waters, both OMZs exhibit slow flux attenuation between 100 and 1000 m where suboxic waters reside, and sequester carbon beneath 1000 m more than twice as efficiently. Using a mechanistic model of particle sinking, remineralization, and disaggregation, we show that three different mechanisms might explain the shape of the OMZ flux profiles: (i) a significant slow-down of remineralization when carbon oxidation transitions from aerobic to anaerobic respiration (e.g., denitrification); (ii) the exclusion of zooplankton that mediate disaggregation of large particles from suboxic waters, and (iii) the limitation of remineralization by the diffusive supply of oxidants (oxygen and nitrate) into large particles. We show that each mechanism leaves a unique signature in the size distribution of particles, suggesting that observations with optical instruments such as Underwater Vision Profilers hold great promise for understanding the drivers of efficient carbon transfer though suboxic water columns. In turn, this will allow more accurate prediction of future changes in carbon sequestration as the ocean loses oxygen in a warming climate.

沉没有机颗粒的再矿化深度通过设置海洋内部再矿化碳的固存时间尺度来控制生物碳泵的效率。氧气最小区域（OMZ）已被确定为深处颗粒迁移增加和有效固碳的区域，但直接测量在这些区域仍然稀疏，仅提供了颗粒通量的快照。在这里，我们使用再矿化示踪剂来重建东部热带太平洋和阿拉伯海的OMZ中的时间平均粒子通量分布。与周围的热带水域相比，两种OMZ都在100至1000 m处存在低氧的水域中表现出较慢的通量衰减，而在1000 m以下的碳固存效率是后者的两倍以上。使用颗粒下沉，再矿化的机械模型，从分解来看，我们发现三种不同的机制可以解释OMZ通量分布的形状：（i）当碳的氧化从有氧呼吸转变为无氧呼吸（例如反硝化）时，矿化作用显着降低。（ii）排除介导大颗粒从低氧水体中解体的浮游动物，以及（iii）通过扩散供应氧化剂（氧气和硝酸盐）进入大颗粒而限制矿化作用。我们表明，每种机制在颗粒的尺寸分布中均具有独特的特征，这表明使用光学仪器（如Underwater Vision Profilers）进行的观测对于了解通过低氧水柱进行有效的碳传输的驱动器具有广阔的前景。反过来，