Efficient Particle Transfer to Depth in Oxygen Minimum Zones of the Pacific and Indian Oceans
Efficient Particle Transfer to Depth in Oxygen Minimum Zones of the Pacific and Indian Oceans
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DOI：
10.3389/feart.2020.00376
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发表时间：
2020-09
期刊：
影响因子：
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通讯作者：
Thomas Weber;D. Bianchi
中科院分区：
文献类型：
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作者：
Thomas Weber;D. Bianchi
下沉的有机颗粒的再矿化深度通过设置海洋内部再矿化碳的封存时间刻度来控制生物碳泵的效率。氧最小区域(OMZ)已被确定为深度颗粒转移和有效碳固存增加的区域，但直接测量在这些区域仍然很少，仅提供颗粒通量的快照。在这里，我们使用再矿化示踪剂重建东热带太平洋和阿拉伯海OMZ的时间平均粒子通量剖面。与周围的热带水域相比，这两个OMZ在亚氧水域所在的100至1000米之间表现出缓慢的通量衰减，并在1000米以下固定碳的效率是前者的两倍多。使用颗粒下沉、再矿化和解聚的机制模型，我们表明有三种不同的机制可以解释OMZ通量分布的形状：(I)当碳氧化从好氧呼吸转变为无氧呼吸(例如反硝化)时，再矿化显著减慢；(Ii)排除浮游动物，介导大颗粒从亚氧水域解聚；以及(Iii)通过向大颗粒扩散供应氧化剂(氧气和硝酸盐)来限制再矿化。我们发现，每种机制都在颗粒的尺寸分布中留下了独特的特征，这表明使用水下视觉剖面仪等光学仪器的观测对于理解通过亚氧水柱进行高效碳转移的驱动因素很有希望。反过来，这将使人们能够更准确地预测未来碳封存的变化，因为海洋在变暖的气候中失去了氧气。
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.