Biogenic silica (bSi) standing stocks and carbon (C) biomass of small plankton are rarely studied together in previous analyses, especially in oligotrophic gyres. Within the oligotrophic western tropical North Pacific, based on size-fractionated bSi and biovolume-derived C analyses in three size fractions (i.e., 0.2-2 µm; 2-20 µm; >20 µm), we observed that picophytoplankton (2 μm) to total bSi standing stocks and living C biomass were 9% and 16%, respectively, suggesting that the role of diatoms in marine Si and C cycles may have been overestimated in previous analyses. Due to the overwhelming predominance of picocyanobacteria in the oligotrophic western tropical North Pacific, their contributions to total bSi stocks and C biomass were quantitatively important and accounted for more of the bSi and C associated with living cells than did diatoms. In addition, water temperature and light intensity were likely the key determinants of the variations in size-fractionated bSi standing stocks and living C biomass, but not nutrient availability. Collectively, these findings encourage a reconsideration of the previously underestimated role of small plankton in understanding the Si and C cycles in the ocean, and may provide insights into the interpretations of disproportionate budgets of Si and C in oligotrophic oceans.

中文翻译：

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西热带北太平洋尺寸分级的生物硅原存量和碳生物量：证明微型浮游生物在贫营养环流中的生态重要性的证据

在以前的分析中，很少同时研究小型浮游生物的生物二氧化硅 (bSi) 常备种群和碳 (C) 生物量，尤其是在贫营养环流中。在贫营养的西热带北太平洋，基于三个尺寸部分（即 0.2-2 µm；2-20 µm；>20 µm）的尺寸分级 bSi 和生物体积衍生的 C 分析，我们观察到微型浮游植物（2 µm）与总 bSi 常备库和活 C 生物量的比例分别为 9% 和 16%，这表明硅藻在海洋 Si 和 C 循环中的作用在之前的分析中可能被高估了。由于在贫营养的西热带北太平洋中微蓝藻的压倒性优势，它们对总 bSi 储量和 C 生物量的贡献在数量上很重要，并且与硅藻相比，与活细胞相关的 bSi 和 C 占更多。此外，水温和光照强度可能是大小分级 bSi 常备种群和活 C 生物量变化的关键决定因素，但不是养分可用性。总的来说，这些发现鼓励重新考虑先前被低估的小型浮游生物在理解海洋中硅和碳循环中的作用，并可能为解释贫营养海洋中硅和碳不成比例的预算提供见解。