Estimating Carbon Flux From Optically Recording Total Particle Volume at Depths Below the Primary Pycnocline
Estimating Carbon Flux From Optically Recording Total Particle Volume at Depths Below the Primary Pycnocline
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根据光学记录初级密度跃层以下深度的总颗粒体积估算碳通量
DOI：
10.3389/fmars.2019.00778
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发表时间：
2019
影响因子：
3.7
通讯作者：
G. Herndl
中科院分区：
文献类型：
--
作者：
Alexander B. Bochdansky;R. Dunbar;Dennis A. Hansell;G. Herndl
光学仪器可以快速、灵敏地测定水柱颗粒的数量和特性。在这里，我们展示了光学评估的主要跃层以下的总颗粒体积在估计两个系统中的碳出口的有效性：开放的亚北极北大西洋和南极洲的罗斯海。这两个区域都表现出季节性的高浮游植物产量和高效的出口(即，强大的生物泵)。中大洋(200-300m)和上覆表层混合层(50-60m)的总颗粒体积显著相关，表明大部分表层颗粒反映了表层的输出。然而，这种连通性受到水柱的物理结构和颗粒类型的调节(例如，南极棕囊藻与硅藻的菌落的存在)。来自这两个地区的证据表明，强烈的跃层可以延缓甚至可能阻止颗粒沉降到更深的层，然后颗粒会屈服于崩解，或者微生物和/或浮游动物的消耗。罗斯海强烈的赤道风可能会加深混合层，导致粒子通过混合层泵快速转移到中大洋深处。根据上层水柱碳质量平衡对罗斯海季节性综合出口产量的独立估计与1)来自图像的总颗粒体积、2)颗粒有机碳和3)叶绿素荧光显著相关(按共同方差顺序)，所有这些都记录在200-300米深度范围内。碳输出与库尔特计数器在相同深度范围内测量的颗粒丰度没有显著相关性。因此，测量初级跃层以下的总颗粒体积是估计碳出口的有用方法，至少在颗粒出口季节性较高的地区是这样。
Optical instruments can rapidly determine numbers and characteristics of water column particles with high sensitivity. Here we show the usefulness of optically assessed total particle volume below the main pycnocline to estimate carbon export in two systems: the open subarctic North Atlantic and the Ross Sea, Antarctica. Both regions exhibit seasonally high phytoplankton production and efficient export (i.e., a strong biological pump). Total particle volumes in the mesopelagic (200-300 m) were significantly correlated with those in the overlying surface mixed layer (50 - 60 m), indicating that most particles at depth reflect export from the surface. This connectivity, however, is modulated by the physical structure of the water column and by particle type (e.g., the presence of colonies of the haptophyte Phaeocystis antarctica versus diatoms). Evidence from both regions show that a strong pycnocline can delay or may even prevent particles from settling to deeper layers, which then succumb to disintegration, or microbial and/or zooplankton consumption. Strong katabatic winds in the Ross Sea may deepen the mixed layer, causing a rapid transfer of particles to mesopelagic depths through the mixed-layer pump. Independent estimates of seasonally integrated export production in the Ross Sea, based on upper water column carbon mass balance, were significantly correlated (in the order of shared variance) with 1) total particle volumes from images, 2) particulate organic carbon, and 3) chlorophyll fluorescence, all recorded at a depth range of 200 – 300 m. Carbon export was not significantly correlated with particle abundance measured by a Coulter Counter at the same depth range. Measuring total particle volume below the primary pycnocline is therefore a useful approach to estimate carbon export at least in regions characterized by seasonally high particle export.