High-resolution opal records from the eastern tropical Pacific provide evidence for silicic acid leakage from HNLC regions during glacial periods
High-resolution opal records from the eastern tropical Pacific provide evidence for silicic acid leakage from HNLC regions during glacial periods
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DOI：
10.1016/j.quascirev.2011.02.002
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发表时间：
2011-05
影响因子：
4
通讯作者：
E. Arellano‐Torres;L. Pichevin;R. Ganeshram
中科院分区：
文献类型：
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作者：
E. Arellano‐Torres;L. Pichevin;R. Ganeshram
从碳酸盐为主的初级生产到二氧化硅为主的初级生产的转变可能会显着影响海洋碳循环通过颗粒碳雨率比（有机碳：Cinorganicfluxs）的变化。C雨率比的增加被用来解释较低的glacialpCO 2;然而，缺乏在末次冰期向二氧化硅为主的生产力的生态转变的确凿证据。在这里，我们提出了新的高分辨率重建的生物硅和总产量在过去的40,000年BP在3个核心从东热带北太平洋（ETNP）墨西哥和尼加拉瓜。这些记录揭示了一个明确的区域模式，更高的硅质生产力与更高的蛋白石积累在末次冰期相比，间冰期。在这些记录中，冰川沉积物中较高的Si：C和Si：N比表明硅质产量在总产量中净增加。我们将此归因于ETNP边缘有利于硅藻而不是其他非硅质藻类的额外的草酸供应。这一建议增加供应的硅在冰期是一致的建议大规模的重新分配过量的硝酸盐从高硝酸盐低叶绿素（HNLC）地区，如赤道东太平洋（EEP）和南大洋的硅酸泄漏假说（SALH）。在这些HNLC区，硅藻硅藻壳的Si同位素组成（δ 30 Si）提供了证据，在硅藻生长过程中，在较高的铁有效性的条件下，在冰期。我们认为，从HNLC区域到邻近海洋的碳酸泄漏可能增加了碳雨率比，并最终导致冰川大气pCO 2的减少。
A shift from carbonate- to silica-dominated primary production could significantly affect the oceanic carbon cycle via changes in the particulate carbon rain-rate ratio ( Corganic:Cinorganicfluxes). An increase in C rain rate ratio has been invoked to explain lower glacialpCO2; however, firm evidence of an ecological shift towards silica-dominated productivity during the last glacial period is lacking. Here, we present new high-resolution reconstructions of biogenic silica and total production over the past 40,000 yr BP in 3 cores from the eastern tropical North Pacific (ETNP) off Mexico and Nicaragua. These records reveal a clear regional pattern of higher siliceous productivity with higher opal accumulation during the last glacial period compared to interglacial times. Higher Si:C and Si:N ratios of glacial sediments in these records suggest a net increase in siliceous production over total production. We attribute this to the additional supply of silicic acid to the ETNP margins favouring diatoms over other non-siliceous algae. This suggestion for increased supply of Si during glacial periods is consistent with the proposed large-scale redistribution of excess silicic acid from High Nitrate Low Chlorophyll (HNLC) regions like the eastern equatorial Pacific (EEP) and the Southern Ocean by the Silicic Acid Leakage Hypothesis (SALH). In these HNLC regions, the Si-isotope composition of diatom frustules (δ30Si) has provided evidence for the generation of surplus of silicic acid during diatom growth under conditions of higher Fe availability during glacial periods. We suggest that silicic acid leakage from the HNLC regions to the adjoining oceans may have increased the carbon rain rate ratio and ultimately, contributed to the decrease in glacial atmosphericpCO2.