The Southern Ocean hosts a large diversity of diatoms that play a major role in carbon fluxes. How the seasonal dynamics in the abundance of specific taxa in surface waters are linked to their contribution to carbon export remains, however, poorly understood. We present here synchronized observations from autonomous samplers deployed in the mixed layer (42 m) and at depth (300 m) during an entire productive season (October 2016 to March 2017) in the iron fertilized region of the central plateau of Kerguelen. Microscopic observations of surface water collected every 11 d revealed 30 different diatom taxa, each contributing to > 1% of total carbon biomass throughout the season. The synchronized sampling revealed a common pattern for diatom taxa belonging to 12 different genera, consisting, for a given taxon, in short pulses of abundance in surface waters followed by export. We explain these coupled dynamics by the formation of aggregates that are produced when a critical diatom cell abundance is reached. This control of the maximum abundance of a given diatom drives the seasonal change in the slope of the size‐class distribution of the diatom community. It further constrains the total carbon diatom biomass in a narrow range of values due to the inverse relationship between total diatom abundance and their community‐weighted mean biomass. This coupling let us conclude that aggregate formation, and the export to depth, occurs throughout the season for diatoms with different morphologies.

中文翻译：

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同步自主采样揭示了南大洋中生物量的脉冲耦合和形态不同的硅藻的输出

南大洋拥有各种各样的硅藻，它们在碳通量中起主要作用。然而，人们对地表水中大量特定分类单元的季节性动态如何与其对碳出口的贡献之间的联系仍然存在。我们在这里展示了在整个生长期（2016年10月至2017年3月）在克格伦中央高原的铁肥区中部署在混合层（42 m）和深度（300 m）中的自主采样器的同步观测结果。每11天收集一次的地表水的显微镜观察结果显示，有30种不同的硅藻类群，每个硅藻类占整个季节总碳生物量的1％以上。同步采样显示了属于12个不同属的硅藻类群的常见模式，对于给定的类群而言，在地表水中短暂的大量脉冲，然后出口。我们通过达到临界硅藻细胞丰度时产生的聚集体的形成来解释这些耦合动力学。对给定硅藻的最大丰度的这种控制驱动了硅藻群落大小分类分布的斜率的季节性变化。由于总硅藻丰度与其群落加权平均生物量之间存在反比关系，因此它将总碳硅藻生物量限制在一个狭窄的值范围内。这种耦合使我们得出结论，在整个季节中，具有不同形态的硅藻会发生聚集体形成和向深处的出口。对给定硅藻的最大丰度的这种控制驱动了硅藻群落大小分类分布的斜率的季节性变化。由于总硅藻丰度与其群落加权平均生物量之间存在反比关系，因此它将总碳硅藻生物量限制在一个狭窄的值范围内。这种耦合使我们得出结论，在整个季节中，具有不同形态的硅藻会发生聚集体形成和向深处的出口。对给定硅藻的最大丰度的这种控制驱动了硅藻群落大小分类分布的斜率的季节性变化。由于总硅藻丰度与其群落加权平均生物量之间存在反比关系，因此它将总碳硅藻生物量限制在一个狭窄的值范围内。这种耦合使我们得出结论，在整个季节中，具有不同形态的硅藻会发生聚集体形成和向深处的出口。