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、低叶绿素沃茨进行的铁富集实验的结果表明，这些地区的浮游植物生长和生物量受到可用铁浓度低的限制。一个关键的共同结果，几乎所有的船上铁富集实验从所有铁有限的地区是硅藻的刺激程度比其他浮游植物类群。在IlronEx 11期间观察到硅藻对其他类群的相同优先刺激，其中在赤道的原位铁施肥产生了以硅藻为主的水华。尽管这样一个一致的强烈反应的硅藻铁此外，影响的铁限制硅藻二氧化硅生产原位仍然unexamined.Dr. Brzezinski将研究影响原位铁施肥对二氧化硅生产和动力学的Si（OH）4使用在南大洋的极前地区与SOFeX项目由莫斯兰丁海洋实验室领导。南大洋是地球上最大的HNLC区域。在所有的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的积累发生在那里，形成了环绕南大洋大部分地区的大沉积蛋白石带。此外，该实验室还从两个独立的HNLC区域产生了第一批数据，这些数据表明硅藻二氧化硅生产对添加的Fe和Zn的强烈反应。考虑到硅藻生长对铁富集的强烈反应，我们新的直接观察结果表明，铁的加入增强了极地锋的二氧化硅生产，以及硅藻在南大洋浮游植物中的主导地位，他们预计硅藻二氧化硅生产的刺激将是SOFeX期间对铁施肥的最明显的生物地球化学反应之一。这一结果将对控制二氧化硅生产速率的机制以及硅藻对现代海洋二氧化硅循环主导区域碳通量的贡献产生强烈影响。

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.