The upper ocean silicon cycle of the subarctic Pacific during the EXPORTS field campaign
The upper ocean silicon cycle of the subarctic Pacific during the EXPORTS field campaign
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DOI：
10.1525/elementa.2021.00087
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
M. Brzezinski;D. Varela;B. Jenkins;K. Buck;Sile M. Kafrissen;Janice L. Jones
中科院分区：
文献类型：
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作者：
M. Brzezinski;D. Varela;B. Jenkins;K. Buck;Sile M. Kafrissen;Janice L. Jones
硅藻是海洋初级生产力和碳输出的主要贡献者，因为它们在高营养环境中快速生长，并且具有重硅压载。他们的贡献是高度修改在高营养低叶绿素地区，由于低铁（Fe）造成的上层海洋硅和碳循环的脱钩。在美国航天局遥感海洋出口过程实地研究期间，在亚北极太平洋东北部HNLC区域的Papa海洋站对硅循环和硅藻在生物碳泵中的作用进行了研究。采样发生在每年最低的表面硅酸（Si（OH）4）浓度。尽管Si（OH）4浓度高达约15 μM，但生物硅（bSi）浓度很低，在数十纳摩尔范围内。平均而言，>5.0-µm粒度部分主导了硅动力学，与小部分（0.6-5.0 μm）相比，占bSi储备的65%和Si吸收的81%。在小的，但不是大的，尺寸部分中检测到的Si吸收的限制。在小硅藻的生长速率是有限的铁，而他们的硅吸收的限制由Si（OH）4浓度，而较大的硅藻只生长限制由铁。大约三分之一的bSi产品出口到了100米以上的地区。硅藻对碳输出的贡献（9-13%）是其对初级生产力贡献（3-7%）的两倍。低bSi生产，低硅藻初级生产力和高bSi输出效率在OSP的组合更类似于在亚热带环流的动态比其他高营养低叶绿素区。
Diatoms are major contributors to marine primary productivity and carbon export due to their rapid growth in high-nutrient environments and their heavy silica ballast. Their contributions are highly modified in high-nutrient low-chlorophyll regions due to the decoupling of upper-ocean silicon and carbon cycling caused by low iron (Fe). The Si cycle and the role of diatoms in the biological carbon pump was examined at Ocean Station Papa (OSP) in the HNLC region of the northeastern subarctic Pacific during the NASA EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field study. Sampling occurred during the annual minimum in surface silicic acid (Si(OH)4) concentration. Biogenic silica (bSi) concentrations were low, being in the tens of nanomolar range, despite high Si(OH)4 concentrations of about 15 μM. On average, the >5.0-µm particle size fraction dominated Si dynamics, accounting for 65% of bSi stocks and 81% of Si uptake compared to the small fraction (0.6–5.0 μm). Limitation of Si uptake was detected in the small, but not the large, size fraction. Growth rate in small diatoms was limited by Fe, while their Si uptake was restricted by Si(OH)4 concentration, whereas larger diatoms were only growth-limited by Fe. About a third of bSi production was exported out of the upper 100 m. The contribution of diatoms to carbon export (9–13%) was about twice their contribution to primary productivity (3–7%). The combination of low bSi production, low diatom primary productivity and high bSi export efficiency at OSP was more similar to the dynamics in the subtropical gyres than to other high-nutrient low-chlorophyll regions.