Diatoms (> 2 μm) have traditionally been identified as the primary biological agents linking the carbon (C) and silicon (Si) cycles. However, recent research has shown that picophytoplankton species (< 2 μm) also play a crucial role in the intertwined Si-C biogeochemical cycling in marine ecosystems. In this study, we examined the spatial distribution and vertical variation of micro/nano-diatoms and picophytoplankton in the eastern Indian Ocean (EIO), aimed to differentiate the contributions of living carbon and biogenic silica (bSi) stocks between diatoms and picophytoplankton. The study revealed that the abundance of picophytoplankton surpasses that of diatoms by four to seven orders of magnitude. Synechococcus was predominantly presented in the upper layer, while Prochlorococcus, picoeukaryotes, and diatoms were primarily located in the middle layer. Aggregation Boosted Tree (ABT) and Generalized Additive Models (GAM) analyses revealed that temperature and silicate (DSi) levels strongly influenced the diatom and picophytoplankton communities in the EIO. The fractions smaller than 2 μm made substantial contributions of 86.20%, 55.69%, and 96.86% to chlorophyll a (Chl-a), particulate organic carbon (POC), and living carbon biomass, respectively, underscoring the ecological significance of picophytoplankton in the carbon cycle of oligotrophic regions. Picophytoplankton represented a 33.06% of bSi stocks in the area, comparable to the contribution of diatoms (> 20 μm). Moreover, estimated contributions of diatom living carbon and silicon quota averaged 0.47% and 0.66%, respectively, while that of Synechococcus stood at 2.58% and 1.77%, indicating the predominance of Synechococcus as a weakly siliceous organism with high cell abundance in oligotrophic seas. Overall, this study draws on data from diatom and picophytoplankton biomass in the EIO to offer insights into the disproportionate carbon and silicon budgets in oligotrophic oceans from a biological perspective.

中文翻译：

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超微型浮游植物是贫营养东印度洋生物碳和生物硅库的主要贡献者


硅藻 (> 2 μm) 传统上被认为是连接碳 (C) 和硅 (Si) 循环的主要生物制剂。然而，最近的研究表明，超微型浮游植物物种 (< 2 μm) 在海洋生态系统中相互交织的 Si-C 生物地球化学循环中也发挥着至关重要的作用。在这项研究中，我们研究了东印度洋微/纳米硅藻和超微型浮游植物（EIO）的空间分布和垂直变化，旨在区分硅藻和超微型浮游植物之间的活性碳和生物硅（bSi）库的贡献。研究表明，微型浮游植物的丰度比硅藻高出四到七个数量级。聚球藻主要存在于上层，而原绿球藻、超微核生物和硅藻主要位于中层。聚合提升树 (ABT) 和广义加性模型 (GAM) 分析表明，温度和硅酸盐 (DSi) 水平强烈影响 EIO 中的硅藻和超微型浮游植物群落。小于2μm的部分对叶绿素a（Chl-a）、颗粒有机碳（POC）和活性碳生物量的贡献分别为86.20%、55.69%和96.86%，强调了超微型浮游植物在海洋中的生态意义。寡营养区的碳循环。微型浮游植物占该地区 bSi 种群的 33.06%，与硅藻的贡献相当 (> 20 μm)。此外，硅藻活性碳和硅配额的估计贡献平均分别为0.47%和0.66%，而聚球藻的贡献量为2.58%和1.77%，表明聚球藻是贫营养海洋中细胞丰度较高的弱硅质生物体。 总的来说，这项研究利用了 EIO 中硅藻和超微型浮游植物生物量的数据，从生物学角度深入了解寡营养海洋中不成比例的碳和硅预算。