Sinking flux of particulate organic matter in the oceans: Sensitivity to particle characteristics
Sinking flux of particulate organic matter in the oceans: Sensitivity to particle characteristics
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DOI：
10.1038/s41598-020-60424-5
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发表时间：
2020-03-27
影响因子：
4.6
通讯作者：
Mahadevan, Amala
中科院分区：
文献类型：
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作者：
Omand, Melissa M.;Govindarajan, Rama;Mahadevan, Amala
海洋上层阳光照射产生的有机颗粒的下沉形成了海洋生物泵的重要组成部分，影响了中层海洋的碳固存和营养物质的补给。从海洋上层倾泻而出的颗粒物会被其表面和内部定殖的细菌再矿化，导致有机物的下沉通量随深度的增加而减弱。在这里，我们为由一系列下沉、再矿化颗粒构成的与深度相关的下沉颗粒质量通量制定了一个机械模型。与之前的研究一样，我们发现该模型无法使用单一类型的颗粒实现特征“马丁曲线”通量分布，而是需要颗粒尺寸和/或属性的分布。我们考虑了适合固体/致密颗粒以及具有缺氧或含氧内部的聚集体的各种再矿化功能形式。我们探索了通量形状与深度剖面对再矿化函数、相对颗粒密度、颗粒尺寸分布和水柱密度分层的选择的敏感性，并发现幂律函数和指数函数都不能提供对建模剖面的绝对优越的拟合。该剖面还对粒子源的时间历史敏感。 3天内变化的表面颗粒尺寸分布（通过颗粒数谱的斜率）代表短暂的浮游植物大量繁殖，导致下沉质量通量的瞬时地下最大值或脉冲。这项工作有助于建立越来越多的机械出口通量模型，为将潜在的动力学和生物过程纳入全球碳循环模型提供了范围。
The sinking of organic particles produced in the upper sunlit layers of the ocean forms an important limb of the oceanic biological pump, which impacts the sequestration of carbon and resupply of nutrients in the mesopelagic ocean. Particles raining out from the upper ocean undergo remineralization by bacteria colonized on their surface and interior, leading to an attenuation in the sinking flux of organic matter with depth. Here, we formulate a mechanistic model for the depth-dependent, sinking, particulate mass flux constituted by a range of sinking, remineralizing particles. Like previous studies, we find that the model does not achieve the characteristic 'Martin curve' flux profile with a single type of particle, but instead requires a distribution of particle sizes and/or properties. We consider various functional forms of remineralization appropriate for solid/compact particles, and aggregates with an anoxic or oxic interior. We explore the sensitivity of the shape of the flux vs. depth profile to the choice of remineralization function, relative particle density, particle size distribution, and water column density stratification, and find that neither a power-law nor exponential function provides a definitively superior fit to the modeled profiles. The profiles are also sensitive to the time history of the particle source. Varying surface particle size distribution (via the slope of the particle number spectrum) over 3 days to represent a transient phytoplankton bloom results in transient subsurface maxima or pulses in the sinking mass flux. This work contributes to a growing body of mechanistic export flux models that offer scope to incorporate underlying dynamical and biological processes into global carbon cycle models.