Si Cycling and Si Control of New Production and Organic Carbon Export in the Southern Ocean and the Sargasso Sea: A JGOFS Synthesis

最近在马尾藻海、赤道太平洋和南大洋等非常不同的系统中进行的几项研究表明，硅藻是表层沃茨新生产和出口生产的主要原因。 这些观察结果，结合硅藻对二氧化硅（Si）的绝对生长需求，表明溶解硅的可用性可能会调节大部分海域的新产量和出口产量。 因此，在海洋上层的碳和氮循环模型必须纳入硅控制硅藻prodctivity和有机质的出口，如果他们的目标是预测海洋的生物响应自然和人为强迫。 由于缺乏有关调控硅循环的因素的数据，这项任务目前对大多数海洋来说是不可能的（例如硅生产率、硅溶解率和硅对硅藻生产力的限制）。PI将综合美国和法国JGOFS计划期间获得的几个大型数据集，并使用新开发的物理/地球化学模型，该模型明确包括硅对硅藻生产力的调节，首次以数据为基础确定海洋上层200-500米硅循环的控制因素。 他们将研究硅循环特征的变化如何影响硅藻从地表沃茨输出碳和氮的能力。 通过数据综合和数值建模的结合，PI将：1）确定那些是海洋上层硅循环特征的最强决定因素的过程，（2）评估硅循环中的差异如何影响硅藻对新产量和出口产量的贡献。结果将为下一代全球海洋碳地球化学模型奠定基础循环，必须明确纳入硅调节碳和氮输出的系统中，硅藻生产力是有限的硅。

Several recent studies in very different systems, such as the Sargasso Sea, Equatorial Pacific and Southern Ocean, have shown that diatoms are responsible for much of the new and export production in surface waters. Those observations, combined with the diatoms' absolute growth requirement for silica (Si), suggest that the availability of dissolved SI may regulate new and export production in much of the sea. Models of carbon and nitrogen cycling in the upper ocean must therefore incorporate Si control of diatom prodctivity and organic-matter export if their goal is to predict the biological response of the oceans to natural and anthropogenic forcing. That task is currently impossible for most of the ocean due to the scarcity of data regarding factors regulating Si cycling (e.g. Si production rates, Si dissolution rates and Si limitation of diatom productivity).The PIs will synthesize several large data sets obtained during the U.S. and French JGOFS programs and use a newly developed physical/biogeochemical model, which explicitly inclues silica regulation of diatom productivity, to make the first data-based determination of the factors controlling the cycling of Si in the upper 200-500 m of the ocean. They will investigate how changes in the character of the Si cycle affect the ability of diatoms to contribute to carbon and nitrogen export from surface waters. Through a combination of data synthesis and numerical modeling the PIs will: 1) identify those processes that are the strongest determinants of the character of the Si cycle in the upper ocean, and2) assess how the resulting differences in the Si cycle affect the ability of diatoms to contribute to new and export production.The results will establish a foundation for the next generation of global biogeochemical models of marine carbon cycling, which must explicitly incorporate Si regualtion of carbon and nitrogen export in systems where diatom productivity is limited by Si.