Iron Limitation of Silica Production in the Southern Ocean: A Companion Proposal to the SOFeX Experiment

在赤道太平洋、亚北极太平洋和最近在南大洋的高硝酸盐、低叶绿素（HNLC）水域进行的铁富集实验结果表明，这些地区的浮游植物生长和生物量受到有效铁浓度低的限制。从所有铁限制区域进行的几乎所有船上铁富集实验的一个关键结果是，硅藻受到的刺激程度比其他浮游植物类群更大。在IlronEx 11期间观察到硅藻对其他分类群的同样优先刺激，在赤道的原位铁施肥产生了以硅藻为主的水华。尽管硅藻对铁的添加有如此一致的强烈反应，但限制铁对硅藻原位二氧化硅生产的影响仍未得到研究。布热津斯基将与Moss Landing海洋实验室领导的SOFeX项目合作，研究原位铁施肥对南大洋极地锋区二氧化硅生产和Si(OH)4使用动力学的影响。南大洋是地球上最大的HNLC区域。在所有HNLC区域中，硅藻在南大洋可能是重要的，因为超过一半的现代全球硅质沉积物积聚发生在那里，形成了环绕大部分南大洋的大沉积蛋白石带。最近AESOPS项目的数据表明，铁和硅都能调节极地锋的硅藻生物量和二氧化硅产量。此外，该实验室已经从两个独立的HNLC区域获得了第一批数据，证明硅藻二氧化硅生产对添加铁和锌的强烈响应。考虑到硅藻生长对铁富集的强烈响应，我们新的直接观察结果表明，铁的添加增加了极地锋的二氧化硅产量，并且硅藻在南大洋浮游植物中占主导地位，他们预计硅藻二氧化硅产量的刺激将是SOFeX期间铁施肥最显著的生物地球化学响应之一。这一结果将对控制硅藻生成速率的机制和硅藻对碳通量的贡献产生重大影响，而硅藻对现代海洋硅藻循环起主导作用。

The results of iron enrichment experiments in the high nitrate, low chlorophyll (HNLC) waters of the Equatorial Pacific, the Subarctic Pacific and most recently in the Southern Ocean demonstrate that phytoplankton growth and biomass in those areas is limited by low concentrations of available iron. A key result common to almost all shipboard Fe enrichment experiments from all Fe-limited regions is that diatoms are stimulated to a greater degree than are other phytoplankton taxa. The same preferential stimulation of diatoms over other taxa, was observed during IlronEx 11 where an in situ iron fertilization in the equatorial produced a bloom dominated by diatoms. Despite such a consistent strong response of diatoms to iron addition, the effects of Fe limitation on diatom silica production in situ remains un-examined.Dr. Brzezinski will examine the effect of in situ iron fertilization on silica production and the kinetics of Si(OH)4 use in the Polar Front region of the Southern Ocean in conjunction with the SOFeX projects led by Moss Landing Marine Laboratory. The Southern Ocean is the largest HNLC region on Earth. Of all the HNLC areas, diatoms are likely to be important in the Southern Ocean as over half of modem global accumulation of siliceous sediment occurs there forming the Great Sedimentary Opal Belt that girdles most of the Southern Ocean.Data from the recent AESOPS program indicate that Fe and Si both regulate diatom biomass and silica production in the Polar Front. In addition, this laboratory has produced the first data from two separate HNLC regions that demonstrate a strong response of diatom silica production to added Fe and Zn. Given the strong response of diatom growth to iron enrichment observed in several HNLC regions in the past, our new direct observations that additions of Fe enhance silica production in the Polar Front and the dominance of diatoms in the phytoplankton of the Southern Ocean, they anticipate that stimulation of diatom silica production will be one of the most pronounced biogeochemical responses to Fe fertilization during SOFeX. That result will have strong implications for the mechanisms controlling silica production rates and the contribution of diatoms to carbon flux in the very region that dominates the silica cycle of the modem ocean.