Deep ocean nutrients during the Last Glacial Maximum deduced from sponge silicon isotopic compositions
Deep ocean nutrients during the Last Glacial Maximum deduced from sponge silicon isotopic compositions
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DOI：
10.1016/j.epsl.2010.02.005
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发表时间：
2010-04-01
影响因子：
5.3
通讯作者：
Halliday, Alex N.
中科院分区：
文献类型：
--
作者：
Hendry, Katharine R.;Georg, R. Bastian;Halliday, Alex N.
南大洋内生物和物理过程对于冰期-间冰期时间尺度上碳和大气 pCO(2) 储存的相对重要性仍不确定。过去了解地表生物生产对碳输出的影响依赖于重建上涌深水的营养供应。特别是，硅酸（Si(OH)(4)）的上升与南大洋通过硅藻生产力的碳输出紧密相关。在这里，我们讨论如何使用深海海绵的硅同位素组成来重建深水 Si(OH)(4) 浓度的变化。我们报告了现代深海海绵骨针的 delta Si-30 并表明它们反映了海水 Si(OH)(4) 浓度。海绵δ Si-30 与海水δ Si-30 的分馏因子与Si(OH)(4) 呈正相关，这可能是生长速率效应。在斯科舍海的两个下岩心记录中应用这一替代指标表明，末次盛冰期 (LGM) 期间南大洋深处的 Si(OH)(4) 浓度与今天没有什么不同。我们的结果并不支持末次盛冰期期间孤立的深海水库中碳和营养物积累的耦合。我们的数据，结合硅藻稳定同位素的记录，只有在硅藻硅化同时减少或从硅质向有机壁浮游植物转变的情况下，才与末次盛冰期南大洋养分利用的增强相一致。 (C) 2010 Elsevier B.V. 保留所有权利。
The relative importance of biological and physical processes within the Southern Ocean for the storage of carbon and atmospheric pCO(2) on glacial-interglacial timescales remains uncertain. Understanding the impact of surface biological production on carbon export in the past relies on the reconstruction of the nutrient supply from upwelling deep waters. In particular, the upwelling of silicic acid (Si(OH)(4)) is tightly coupled to carbon export in the Southern Ocean via diatom productivity. Here, we address how changes in deep water Si(OH)(4) concentrations can be reconstructed using the silicon isotopic composition of deep-sea sponges. We report delta Si-30 of modern deep-sea sponge spicules and show that they reflect seawater Si(OH)(4) concentration. The fractionation factor of sponge delta Si-30 compared to seawater delta Si-30 shows a positive relationship with Si(OH)(4), which may be a growth rate effect. Application of this proxy in two down-core records from the Scotia Sea reveals that Si(OH)(4) concentrations in the deep Southern Ocean during the Last Glacial Maximum (LGM) were no different than today. Our result does not support a coupling of carbon and nutrient build up in an isolated deep ocean reservoir during the LGM. Our data, combined with records of stable isotopes from diatoms, are only consistent with enhanced LGM Southern Ocean nutrient utilization if there was also a concurrent reduction in diatom silicification or a shift from siliceous to organic-walled phytoplankton. (C) 2010 Elsevier B.V. All rights reserved.