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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Deep ocean nutrients during the Last Glacial Maximum deduced from sponge silicon isotopic compositions
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Deep ocean nutrients during the Last Glacial Maximum deduced from sponge silicon isotopic compositions

机译：由海绵硅同位素组成推断出的最后一次冰期末期深海营养

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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.
机译：在冰川间时间尺度上，南大洋内生物和物理过程对于碳和大气pCO（2）的存储的相对重要性仍然不确定。过去了解地表生物生产对碳出口的影响依赖于上升深水营养供应的重建。特别是，硅酸（Si（OH）（4））的上升流与硅藻生产力在南大洋的碳出口紧密相关。在这里，我们解决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针的Delta Si-30，并显示它们反映了海水中Si（OH）（4）的浓度。与海水三角洲Si-30相比，海绵三角洲Si-30的分馏因子与Si（OH）（4）呈正相关，这可能是生长速率的影响。在来自斯科舍海的两个下层记录中使用此代理后，发现最后一次冰河极大期（LGM）期间南大洋深处的Si（OH）（4）浓度与今天相同。我们的结果不支持LGM期间孤立的深海储层中碳和养分的累积耦合。如果硅藻硅化同时减少或从硅质浮游植物转变为有机壁浮游植物，我们的数据与硅藻稳定同位素的记录相结合，仅与增强的LGM南方海洋营养素利用相一致。

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